WO2020211952A1

WO2020211952A1 - Client device, network access node and methods for changing radio link monitoring configuration

Info

Publication number: WO2020211952A1
Application number: PCT/EP2019/060170
Authority: WO
Inventors: Chaitanya TUMULA; Rama Kumar MOPIDEVI
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2019-04-18
Filing date: 2019-04-18
Publication date: 2020-10-22
Also published as: CN113748704B; CN113748704A

Abstract

The invention relates to radio link monitoring and when to change the radio link monitoring configuration for a client device (100). The client device (100) performs radio link monitoring for a radio link to a network access node (300) based on a measured quality of the radio link and a first set of parameters. The client device (100) further compares the measured quality of the radio link with a second set of parameters and indicates the comparison of the measured quality of the radio link with at least one parameter of the second set of parameters to the network access node (300). Based on the indication the network access node (300) can determine if the radio link can support a second service associated with the second set of parameters and transmit a first reconfiguration instruction to the client device (100) if the radio link can support the second service. The first reconfiguration instruction instructs the client device (100) to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link. Thereby, the network access node (300) can deliver data associated with the second service to the client device (100) over the radio link. Furthermore, the invention also relates to corresponding methods and a computer program.

Description

CLIENT DEVICE, NETWORK ACCESS NODE AND METHODS FOR CHANGING RADIO LINK MONITORING CONFIGURATION

Technical Field

The invention relates to a client device and a network access node for changing radio link monitoring configuration. Furthermore, the invention also relates to corresponding methods and a computer program.

Background

Radio Link Monitoring (RLM) is a procedure used for monitoring the received signal quality of a radio link between a network access node and a client device. Typically, the network access node configures two threshold values to monitor the received signal quality of the radio link using predefined reference signals. A first threshold value, Qout, at which a client device will go out-of-synchronization (OOS) and a second threshold value, Qin, at which the client device will return to in-synchronization (IS). The Qout and Qin threshold values can be specified in terms of hypothetical physical downlink control channel (PDCCH) block error rate (BLER). For example, Qout can be a received BLER on PDCCH of greater than X%. This is valid also when no PDCCH is received. In that case, a mapping between the BLER and signal-to-noise ratio (SNR) or some other metric of signal quality must be utilized to set the threshold. As long as the estimated performance of the PDCCH, for a given payload size and allocation size (code rate), is less than X%, the radio link is considered to be useful for data transmission. When the estimated BLER is above X%, OOS is declared and the client device ceases to transmit. In particular, the physical layer in the client device signals OOS to higher layers and terminates transmission, when the client device is unable to successfully decode PDCCH at the X% BLER for a number of predefined time intervals specified in the parameter N310. This starts a timer T310 (in seconds). If the client device does not regain IS status before expiry of the timer T310, the client device reports radio link failure and triggers radio resource control (RRC) reconfiguration request, if access stratum (AS) security has been activated. If the AS security has not been activated, the client device moves to idle mode (e.g. RRCJDLE) upon radio link failure.

A higher reception quality is required to return a client device to IS. In particular, after OOS has been declared, an estimated BLER on PDCCH of Y% or less (Qin) is required, where Y<X. The client device must successfully decode PDCCH at this level for a number of predefined time intervals specified in the parameter N31 1 . If the received signal quality is consistently too poor for reliable communications, the client device is preferably“handed over” to a different network access node providing better signal quality. If the client device cannot be handed over, and the received signal quality continues to deteriorate, the client device goes into OOS and the network terminates service to the client device.

Summary

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 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 be connected to a network access node over at least one radio link, and further being configured to

perform radio link monitoring for the radio link based on a measured quality of the radio link, and at least one of a first in-synchronization threshold value and a first out-of- synchronization threshold value included in a first set of parameters;

compare the measured quality of the radio link with at least one of a second in synchronization threshold value and a second out-of-synchronization threshold value included in a second set of parameters;

transmit a first control message to the network access node, wherein the first control message indicates the comparison of the measured quality of the radio link with at least one parameter of the second set of parameters.

That the client device is configured to be connected to a network access node over at least one radio link can herein mean that the client device may be connected to two network access nodes over two radio links, for example as in a dual connectivity mode.

The comparison indicated in the first control message can be a comparison of the measured quality of the radio link with the second in-synchronization threshold value or a comparison of the measured quality of the radio link with the second out-of-synchronization threshold value.

The measured quality can e.g. be a measure signal-to-noise ratio (SNR) of predefined reference signals associated with the radio link. The threshold values can e.g. be specified in terms of hypothetical PDCCH BLER such as a measured or predicted BLER on PDCCH of greater than X%. However, the measured quality can also be any other suitable quality metric.

An advantage of the client device according to the first aspect is that by comparing the measured radio link quality with at least one of the second in-synchronization threshold value and the second out-of-synchronization threshold value, the client device can obtain the information whether a second service associated with the second set of parameters can be supported or not, and transmit this information to the network access node in a first control message to help the network access node make a better decision to maintain the first radio link.

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

compare the measured quality of the radio link with at least one parameter of the second set of parameters upon the start of a timer associated with the radio link monitoring.

The timer associated with the radio link monitoring can be a timer which is started upon determining that the measured quality of the radio link falls below the first out-of- synchronization threshold value. Thus, the timer can e.g. be the timer T310 used in convention radio link monitoring.

An advantage with this implementation form is that the client device can perform the comparison of the measured radio link quality with the parameters of the second set of parameters only after determining that the radio link quality is below the threshold parameters of the first set of parameters and thereby save computing resources.

transmit the first control message to the network access node upon expiry of the timer associated with the radio link monitoring.

An advantage with this implementation form is that the client device need not transmit the information in the first control message to the network access node, if the radio link quality is recovered while the timer associated with radio link monitoring is running. In an implementation form of a client device according to the first aspect, the first control message is a radio resource control, RRC, message or a physical uplink control channel, PUCCH, message.

An advantage with this implementation form is that the client device can send the first control message as a part of RRC signalling if the client device does not support delay critical applications. However, if the client device supports delay critical applications, the first control message can be transmitted using a PUCCH message.

receive a second control message from the network access node, wherein the second control message comprises a first reconfiguration instruction to change from the first set of parameters to the second set of parameters for performing radio link monitoring;

perform radio link monitoring for the radio link based on a measured quality of the radio link and the second set of parameters according to the first reconfiguration instruction.

An advantage with this implementation form is that after reconfiguration of radio link monitoring parameters by the network access node, the client device can still maintain the radio link connection to the network access node.

transmit a third control message to the network access node, wherein the third control message comprises an indication that the measured quality of the radio link is higher than the first in-synchronization threshold value.

An advantage with this implementation form is that while the client device is performing radio link monitoring with respect to the second set of parameters, it can also compare the measured radio link quality against the first set of parameters and inform the network access node if the radio link quality has improved and can support a first service.

receive a fourth control message from the network access node, wherein the fourth control message comprises a second reconfiguration instruction to change from the second set of parameters to the first set of parameters for performing radio link monitoring; perform radio link monitoring for the radio link based on a measured quality of the radio link and the first set of parameters according to the second reconfiguration instruction.

An advantage with this implementation form is that the client device after receiving a fourth control message containing the second reconfiguration instruction can perform the radio link monitoring using the first set of parameters.

In an implementation form of a client device according to the first aspect, the second set of parameters is a default set of radio link parameters for performing radio link monitoring.

That the second set of parameters is a default set of radio link parameters can be understood to mean that the second set of parameters are known to the network access node and the client device such that, after the connection establishment with the network access node, if the client device does not receive any parameter set for radio link monitoring, the client device can use the second set of parameters for radio link monitoring.

In an implementation form of a client device according to the first aspect, the first set of parameters is associated with an ultra-reliable low latency communication service, and the second set of parameters is associated with an enhanced mobile broadband service.

An advantage with this implementation form is that the described procedure can be applied for a predefined mapping of the first and second set of parameters with a specific data service.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a network access node for a wireless communication system, the network access node being configured to be connected to a client device over at least one radio link, and to configure the client device with a first set of parameters for performing radio link monitoring for the radio link, the network access node further being configured to

receive a first control message from the client device, wherein the first control message indicates a comparison of a measured quality of the radio link with at least one parameter of a second set of parameters for performing radio link monitoring;

transmit a second control message to the client device, wherein the second control message comprises a first reconfiguration instruction instructing the client device to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link. The second set of parameters can be known to the client device, e.g. due to the fact that the second set of parameters are default parameters for the client device. Default radio link parameters are known to the network access node and the client device after the radio link establishment. If the client device does not receive any parameter set for radio link monitoring, the client device uses the default radio link parameters for radio link monitoring.

An advantage of the network access node according to the second aspect is that after receiving the first control message from the client device, the network access node can determine if the radio link can support a second service based on the first control message. If the radio link can support the second service, the network access node can reconfigure the radio link monitoring parameters so that the network access node can still deliver data associated with the second service. Thereby, providing uninterrupted service.

In an implementation form of a network access node according to the second aspect, the first set of parameters comprises a first in-synchronization threshold value and a first out-of- synchronization threshold value, and the second set of parameters comprises a second in synchronization threshold value and a second out-of-synchronization threshold value.

An advantage with this implementation form is that by defining two sets of parameters, the two sets of parameters can be mapped to different services. Thereby, the radio link quality can be monitored efficiently and better service can be provided by the network access node.

In an implementation form of a network access node according to the second aspect, the network access node is further configured to

receive a third control message from the client device, wherein the third control message comprises an indication that the measured quality of the radio link is higher than the first in synchronization threshold value;

transmit a fourth control message to the client device, wherein the fourth control message comprises a second reconfiguration instruction instructing the client device to change from the second set of parameters to the first set of parameters for performing radio link monitoring for the radio link.

An advantage with this implementation form is that the network access node can reconfigure the radio link monitoring parameters to the first set of parameters and support a first data service. In an implementation form of a network access node according to the second aspect, the first control message is a RRC message or a PUCCH message.

In an implementation form of a network access node according to the second aspect, the first set of parameters is associated with an ultra-reliable low latency communication service, and the second set of parameters is associated with an enhanced mobile broadband service.

According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for a client device being connected to a network access node over at least one radio link, the method comprises

performing radio link monitoring for the radio link based on a measured quality of the radio link, and at least one of a first in-synchronization threshold value and a first out-of- synchronization threshold value included in a first set of parameters;

comparing the measured quality of the radio link with at least one of a second in synchronization threshold value and a second out-of-synchronization threshold value included in a second set of parameters;

transmitting a first control message to the network access node, wherein the first control message indicates the comparison of the measured quality of the radio link with at least one parameter of the second set of parameters.

The method according to the third 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 third aspect are the same as those for the corresponding implementation forms of the client device according to the first aspect.

According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a network access node being configured to be connected to a client device over at least one radio link, and to configure the client device with a first set of parameters for performing radio link monitoring for the radio link, the method comprises receiving a first control message from the client device, wherein the first control message indicates a comparison of a measured quality of the radio link with at least one parameter of a second set of parameters for performing radio link monitoring;

transmitting a second control message to the client device, wherein the second control message comprises a first reconfiguration instruction instructing the client device to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link.

The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the network access node according to the second aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network access node.

The advantages of the methods according to the fourth aspect are the same as those for the corresponding implementation forms of the network access node according to the second 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 shows a network access node according to an embodiment of the invention;

- Fig. 4 shows a method for a network access node according to an embodiment of the invention; - Fig. 5 shows a wireless communication system according to an embodiment of the invention;

- Fig. 6 shows threshold values of a first set of parameters and a second set of parameters according to an embodiment of the invention;

- Fig. 7 shows signalling between a client device and a network access node according to an embodiment of the invention;

- Fig. 8 illustrates radio link monitoring based on a first set of parameters and a second set of parameters according to an embodiment of the invention; and

- Fig. 9 shows radio link monitoring after reconfiguration according to an embodiment of the invention.

Detailed Description

In 3GPP NR, it has been agreed to support more than one set of threshold parameters Qout and Qin for radio link monitoring. The corresponding text from 3GPP TS 38.133v15.2.0 is reproduced below.

The out-of-sync block error rate (BLERout) and in-sync block error rate (BLERin) are determined from the network configuration via parameter RLM-IS-OOS-thresholdConfig (or rlmlnSyncOutOfSyncThreshold according to 38.331 ) signaled by higher layers. The network can configure one of the two pairs of out-of-sync and in-sync block error rates which are shown in Table 8.1 .1 -1 . When UE is not configured with RLM-IS-OOS-thresholdConfig from the network, UE determines out-of-sync and in-sync block error rates from Configuration #0 in Table 8.1 .1 -1 as default.

Table 8.1.1 -1 : Out-of-sync and in-sync block error rates

The motivation to support two different sets of RLM parameters is to support different services with different QoS requirements.

In conventional solutions, no explicit solution is provided for determining when the network access node can change the RLM threshold values for a client device from a first set to a second set, e.g. from a default set to a new set or vice versa. An implicit method may be one, in which repeated RRC connection re-establishment messages from the client device triggers a change from a first to a second set of RLM thresholds. However, the inventors have identified that in such a method, the network access node does not know if the radio link has sufficient quality to meet the requirements of the second set of RLM threshold values. The network access node can only obtain this knowledge after changing RLM thresholds and after seeing whether RLF is declared or not for the new set of threshold values. To overcome the identified shortcomings of conventional solutions embodiments of the invention provide a solution in which the network access node can change the RLM threshold values for a client device from a first set of RLM parameters to a second set of RLM parameters based on an indication signaled by the client device.

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 communication in a wireless communication system.

That the client device 100 is configured to perform certain actions can 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 be connected to a network access node 300 over at least one radio link, and further being configured to perform radio link monitoring for the radio link based on a measured quality of the radio link, and at least one of a first in-synchronization threshold value and a first out-of-synchronization threshold value included in a first set of parameters. The client device 100 is further configured to compare the measured quality of the radio link with at least one of a second in synchronization threshold value and a second out-of-synchronization threshold value included in a second set of parameters and transmit a first control message 510 to the network access node 300. The first control message 510 indicates the comparison of the measured quality of the radio link with at least one parameter of the second set of parameters.

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 client device 100 is configured to be connected to a network access node 300 over at least one radio link, and the method 200 comprises performing 202 radio link monitoring for the radio link based on a measured quality of the radio link, and at least one of a first in-synchronization threshold value and a first out-of- synchronization threshold value included in a first set of parameters. The method 200 further comprises comparing 204 the measured quality of the radio link with at least one of a second in-synchronization threshold value and a second out-of-synchronization threshold value included in a second set of parameters and transmitting 206 a first control message 510 to the network access node 300. The first control message 510 indicates the comparison of the measured quality of the radio link 602 with at least one parameter of the second set of parameters.

Fig. 3 shows a network access node 300 according to an embodiment of the invention. In the embodiment shown in Fig. 3, the network access node 300 comprises a processor 302, a transceiver 304 and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 by communication means 308 known in the art. The network access node 300 may be configured for both wireless and wired communication in wireless and wired communication systems, respectively. The wireless communication capability is provided with an antenna or antenna array 310 coupled to the transceiver 304, while the wired communication capability is provided with a wired communication interface 312 coupled to the transceiver 304.

That the network access node 300 is configured to perform certain actions can in this disclosure be understood to mean that the network access node 300 comprises suitable means, such as e.g. the processor 302 and the transceiver 304, configured to perform said actions.

According to embodiments of the invention the network access node 300 is configured to be connected to a client device 100 over at least one radio link, and to configure the client device 100 with a first set of parameters for performing radio link monitoring for the radio link. The network access node 300 is further configured to receive a first control message 510 from the client device 100. The first control message 510 indicates a comparison of a measured quality of the radio link 602 with at least one parameter of a second set of parameters for performing radio link monitoring. Furthermore, the network access node 300 is configured to transmit a second control message 512 to the client device 100. The second control message 512 comprises a first reconfiguration instruction instructing the client device 100 to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link.

Fig. 4 shows a flow chart of a corresponding method 400 which may be executed in a network access node 300, such as the one shown in Fig. 3. The network access node 300 is configured to be connected to a client device 100 over at least one radio link, and to configure the client device 100 with a first set of parameters for performing radio link monitoring for the radio link. The method 400 comprises receiving 402 a first control message 510 from the client device 100. The first control message 510 indicates a comparison of a measured quality of the radio link with at least one parameter of a second set of parameters for performing radio link monitoring. The method 400 further comprises transmitting 404 a second control message 512 to the client device 100. The second control message 512 comprises a first reconfiguration instruction instructing the client device 100 to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link.

Fig. 5 shows a wireless communication system 500 according to an embodiment 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. 5 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.

In the wireless communication system 500, the client device 100 is connected to the network access node 300 over at least one radio link 602. Only one radio link 602 is illustrated in Fig. 5 but the invention is not limited thereto. For example, the client device 100 may be connected to more than one network access node 300 over multiple radio link with one radio link corresponding to a connection between the client device 100 and one of the network access nodes 300.

To determine whether the quality of the radio link 602 is suitable for data transmissions, the client device 100 performs radio link monitoring for the radio link 602. The radio link monitoring may be performed based on a first set of parameters or a second set of parameters, i.e. by comparing a measured quality of the radio link 602 with either the first set of parameters or the second set of parameters. The first set of parameters and/or the second set of parameters may be pre-defined in the client device 100 e.g. pre-defined in a standard such as specified by 3GPP. The client device 100 may further be configured with the first set of parameters and/or the second set of parameters, e.g. by the network access node 300. Which one of the two sets of parameters the client device 100 should currently use for radio link monitoring, may be configured for the client device 100 by the network access node 300.

In embodiments, the second set of parameters may be a default set of radio link parameters for performing radio link monitoring. The second set of parameters may e.g. be a default set of radio link parameters pre-defined in a standard, such as 3GPP. In such embodiments, the second set of parameters is known to the client device 100 and can be used by the client device 100 although the client device 100 is configured to perform radio link monitoring based on the first set of parameters. Furthermore, the first set of parameters and the second set of parameters may in embodiments be associated with different services. For example, the first set of parameters may be associated with an ultra-reliable low latency communication service, and the second set of parameters may be associated with an enhanced mobile broadband service. Hence, when the client device 100 supports both URLLC and eMBB services, the network access node 300 may configure the client device 100 with the first set of parameters for radio link monitoring based on the client device’s capability to support URLLC service. If the client device 100 cannot support URLLC services, the network access node 300 may not configure any parameters for radio link monitoring. In such a scenario, the client device 100 should use the default set of parameters for radio link monitoring. Optionally, if the client device 100 cannot support URLLC services, the network access node 300 may configure the client device 100 with the second set of parameters for the radio link monitoring.

In Fig. 5, the client device 100 is configured to perform radio link monitoring for the radio link 602 based on a measured quality of the radio link and the first set of parameters. The quality of the radio link may be measured in a conventional manner and the measure quality can e.g. be a measured SNR of predefined reference signals associated with the radio link 602, where the measured SNR of the predefined reference signals may be mapped to hypothetical PDCCH BLER of the associated control channel. According to embodiments of the invention the client device 100 further compares the measured quality of the radio link with the second set of parameters, i.e. with the set of parameters currently not configured for radio link monitoring. The client device 100 may indicate the comparison of the measured quality of the radio link 602 with at least one parameter of the second set of parameters to the network access node 300. The indication may be comprised in a first control message 510 as will be further described below with reference to Fig. 7. Based on the indication received from the client device 100, the network access node 300 may determine to reconfigure the client device 100 to use the second set of parameters for performing radio link monitoring for the radio link 602. The network access node 300 can reconfigure the client device 100 by transmitting a first reconfiguration instruction to the client device 100. The first reconfiguration instruction may be comprised in a second control message 512 as will be further described below with reference to Fig. 7.

In embodiments, the first set of parameters comprise a first in-synchronization threshold value and a first out-of-synchronization threshold value, and the second set of parameters comprise a second in-synchronization threshold value and a second out-of-synchronization threshold value. Fig. 6 shows an example illustration of the threshold values of the first set of parameters and the second set of parameters according to an embodiment of the invention and the example BLER curves for aggregation level four AL 4 and aggregation level eight AL 8 for PDCCH. In the embodiment shown in Fig. 6, the first set of parameters comprise a first in synchronization threshold value T1 in and a first out-of-synchronization threshold value T1 out and is associated with an URLLC service. The second set of parameters comprise a second in-synchronization threshold value T2in and a second out-of-synchronization threshold value T2out and is associated with an eMBB service. Furthermore, the second set of parameters is the default set of parameters, i.e. the second in-synchronization threshold value T2in and the second out-of-synchronization threshold value T2out are the default threshold values. As shown in Fig. 6, the first in-synchronization threshold value T1 in and the first out-of- synchronization threshold value T1 out are stricter in respect of error rate than the second in synchronization threshold value T2in and the second out-of-synchronization threshold value T2out. For example, if the measured quality of the radio link is above the first out-of- synchronization threshold value Thl out it is also above the second out-of-synchronization threshold value Th2out.

When the client device 100 supports URLLC services together with eMBB services, the network access node 300 may configure the client device 100 with the first set of parameters for radio link monitoring, e.g. during connection setup. The selection of the first set of parameters may e.g. be based on the capability of the client deice 100 to support URLLC services. When configured with the first set of parameters for radio link monitoring, the client device 100 uses the first in-synchronization threshold value T1 in and the first out-of- synchronization threshold value T1 out to evaluate the radio link quality. This ensure that the radio link quality is suitable for both URLLC and eMBB services, as the first set of parameters are stricter than the second set of parameters. The network access node 300 can hence transmit data associated with both services to the client device 100 over the radio link. However, if the quality of the radio link deteriorates, the quality may no longer be suitable for URLLC service but may still be good enough for eMBB services. In such scenarios, it may be beneficial to reconfigure the client device 100 to use the second set of parameters instead of the first set of parameters for radio link monitoring. The invention provides a way to reconfigure the set of parameters used for radio link monitoring based on an indication from the client device 100, as will now be described with reference to Fig. 7.

Fig. 7 shows signalling between the client device 100 and the network access node 300 for reconfiguring the set of parameters used for radio link monitoring according to an embodiment of the invention. In step I, the client device 100 performs radio link monitoring for a radio link based on the measured quality of the radio link, and at least one of the first in-synchronization threshold value and the first out-of-synchronization threshold value included in the first set of parameters. The client device 100 compares the measured quality of the radio link with at least one parameter of the first set of parameters to determine whether the client device 100 is in synchronization or out-of-synchronization. As previously described, the client device 100 may be configured to use the first set of parameters for radio link monitoring e.g. by the network access node 300. The radio link monitoring is performed in a conventional way. Thus, if the measured quality of the radio link falls below the first out-of-synchronization threshold value, the physical layer in the client device 100 sends an out-of-synchronization indication to a higher layer. After a predefined consecutive number of out-of-synchronization indications, a timer is started in the client device. After the timer is started, the client device compares the measured radio link quality with the first in-synchronization threshold. If the client device 100 does not regain in-synchronization while the timer is running, the client device 100 declares radio link failure upon expiry of the timer. The client device 100 further triggers RRC connection re establishment if access stratum security is active.

In step II, the client device 100 compares the measured quality of the radio link with at least one of the second in-synchronization threshold value and the second out-of-synchronization threshold value included in the second set of parameters. The comparison may determine whether the measured quality of the radio link is higher or lower than the second in synchronization threshold value and/or the second out-of-synchronization threshold value. For example, if the measured quality of the radio link is higher than the second in-synchronization threshold value or the second out-of-synchronization threshold value, the first control message 510 may indicate TRUE, otherwise FALSE. Step II may be performed in parallel with step I or be triggered by an event detected in step I such as e.g. the start of the timer described above. Thus, the client device 100 may in embodiments compare the measured quality of the radio link with at least one parameter of the second set of parameters upon the start of the timer associated with the radio link monitoring.

Furthermore, the client device 100 transmits a first control message 510 to the network access node 300, as shown in step III. The first control message 510 indicates the comparison of the measured quality of the radio link with at least one parameter of the second set of parameters performed in step II. In embodiments, the first control message 510 may be a RRC message or a physical uplink control channel (PUCCH) message. The client device 100 may transmit the first control message 510 to the network access node 300 at any time during the comparison of the radio link quality with the second set of parameters. The transmission of the first control message 510 may in embodiments be triggered when an event is detected during the comparison, e.g. that the measured quality is above the second in-synchronization threshold value and/or the second out-of-synchronization threshold value. In embodiments, where the comparison in step II is started upon the start of the timer associated with the radio link monitoring, the client device 100 may transmit the first control message 510 to the network access node 300 upon expiry of the timer associated with the radio link monitoring. For example, include the first control message 510 in a RRC re-establishment message being triggered by the expiry of the timer.

The network access node 300 receives the first control message 510 from the client device 100. In case the first control message 510 is received along with an RRC re-establishment message due to the radio link failure detection associated with the first set of parameters, the network access node 300 may determine if the radio link can support the second service (eMBB) based on the indication in the first control message 510. In case the radio link can support the second service, the network access node 300 may determine that the second set of parameters should be used for radio link monitoring. If the network access node 300 determines to reconfigure the set of parameters for radio link monitoring for the client device 100, the network access node 300 transmits a second control message 512 to the client device 100, as shown in step IV. The second control message 512 comprises a first reconfiguration instruction instructing the client device 100 to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link.

The client device 100 receives the second control message 512 from the network access node 300, and hence the first reconfiguration instruction to change from the first set of parameters to the second set of parameters for performing radio link monitoring. In step V, the client device 100 performs radio link monitoring for the radio link based on the measured quality of the radio link and the second set of parameters according to the first reconfiguration instruction.

While performing radio link monitoring based on the second set of parameters, the client device 100 may additionally in step VI compare the measured quality of the radio link against at least one of the first set of parameters. Based on the comparison against at least one of the first set of parameters the client device 100 may transmit a third control message 514 to the network access node 300, as shown in step VII. The third control message 514 may comprise an indication that the measured quality of the radio link is higher than the first in-synchronization threshold value, i.e. that the measured quality of the radio link is again suitable for services associated with the first set of parameters (first service). The network access node 300 receives the third control message 514 from the client device 100, where the third control message 514 comprises the indication that the measured quality of the radio link is higher than the first in-synchronization threshold value. Based on the indication in the third control message 514, the network access node 300 transmits a fourth control message 516 to the client device 100 in step VIII. The fourth control message 516 comprises a second reconfiguration instruction instructing the client device 100 to change from the second set of parameters to the first set of parameters for performing radio link monitoring for the radio link.

The client device 100 receives the fourth control message 516 from the network access node 300, where the fourth control message 516 comprises the second reconfiguration instruction to change from the second set of parameters to the first set of parameters for performing radio link monitoring. In step IX, the client device 100 performs radio link monitoring for the radio link based on the measured quality of the radio link and the first set of parameters according to the second reconfiguration instruction. Step IX may correspond to step I and the reconfiguration back to radio link monitoring based on the first set of parameters may hence correspond to the procedure described in Fig. 7 being started anew.

Further details related to the invention will now be described with reference to Figs. 8 and 9. Fig. 8 shows radio link monitoring based on the first set of parameters and the second set of parameters according to an embodiment of the invention and Fig. 9 shows radio link monitoring after reconfiguration according to an embodiment of the invention. In the embodiments shown in Figs. 8 and 9, the first set of parameters is associated with an URLLC service, and the second set of parameters is associated with an eMBB service. Furthermore, the second set of parameters is a default set of parameters. As shown in Fig. 8, the client device 100 is at time instance t1 configured to perform radio link monitoring based on the first set of parameters, i.e. based on the first in-synchronization threshold value T1 in and the first out-of-synchronization threshold value T1 out. The radio link monitoring is performed for a radio link with the network access node 300 and the radio link monitoring configuration may be received from the network access node 300. If the measured quality of the radio link falls below the first out-of- synchronization threshold value T1 out, the client device 100 send an out-of-synchronization OOS indication to higher layer. After a number of predefined time intervals N310 of consecutive out-of-synchronization OOS indications are sent, a timer T310 is started. In the embodiment shown in Fig. 8, the number of predefined time intervals N310 is equal to four and hence when four consecutive out-of-synchronization OOS indications have been sent at time instance t2, the timer T310 is started. While the timer T310 is running, the client device 100 continues to perform radio link monitoring based on the first set of parameters to determine in-synchronization status and starts to compare the measured quality of the radio link with the second set of parameters. As previously described, the client device 100 may indicate the comparison with the second set of parameters to the network access node 300 in the first control message 510. The indication of the comparison may e.g. be a TRUE or FALSE indication. In such embodiments, the first control message 510 may e.g. indicate TRUE if the measured quality of the radio link is better than at least one parameter of the second set of parameters, and FALSE if the measured quality of the radio link is worse than at least one parameter of the second set of parameters. In a similar way as for the conventional radio link monitoring, the indication in the first control message 510 may be based on a preconfigured number of consecutive indications that the measured quality of the radio link is better or worse than at least one parameter of the second set of parameters.

In the embodiment shown in Fig. 8, the client device 100 transmits the first control message 510 to the network access node 300 upon expiry of the timer T310 at the time instance t3. However, the first control message 510 may be transmitted at any time. In embodiments, the transmission of the first control message 510 may e.g. be triggered when a preconfigured number of consecutive indications has been detected by the comparison with the second set of parameters.

Upon expiry of the timer T310, the client device 100 further declares radio link failure and triggers RRC connection re-establishment if access stratum security is active. The network access node 300 is thereby informed that the quality of the radio link is worse than the first out- of-synchronization threshold value T1 out and hence that the radio link is no longer suitable for URLLC service. If the indication in the first control message 510 indicates that the measured quality of the radio link is also worse than at least one parameter of the second set of parameters, the network access node 100 may initiate a handover procedure and/or stop both the URLLC and eMBB services to the client device 100. On the other hand, if the indication in the first control message 510 indicates that the measured quality of the radio link is better than at least one parameter of the second set of parameters, the network access node 300 may reconfigure the client device 100 to use the second set of parameters for radio link monitoring. The network access node 300 may further stop transmitting data associated with the URLLC service but continue to transmit data associated with the eMBB service. Fig. 8 shows an embodiment where the network access node 300 determines to reconfigure the radio link monitoring for the client device 100 and therefore transmits the second control message 512 to the client device 100 at the time instance t4. The second control message 512 indicates that the second set of parameters should be used for radio link monitoring.

Fig. 9 shows radio link monitoring after reconfiguration according to an embodiment of the invention. After the reconfiguration at time instance t4 by receiving the second control message 512, the client device 100 performs radio link monitoring based on the second set of parameters, i.e. measures the quality of the radio link and compares it with the second in synchronization threshold value T2in and/or the second out-of-synchronization threshold value T2out. If the measured quality of the radio link falls below the second out-of-synchronization threshold value T2out, the client device 100 sends out-of-synchronization indications to higher layers. If the measured radio link quality is better than the second in-synchronization threshold value T2in, the client device 100 sends send in-synchronization indications to higher layers. Furthermore, the client device 100 compares the measured quality of the radio link with the first in-synchronization threshold value T1 in. If the measured quality of the radio link is higher than the first in-synchronization threshold value T1 in, in a number of predefined time intervals N31 1 , the client device 100 transmits the third control message 514 to the network access node 300, as shown in Fig. 6. The third control message 514 comprises an indication that the measured quality of the radio link is higher than the first in-synchronization threshold value. Hence, the third control message 514 indicates to the network access node 300 that the quality of the radio link has returned to a level that is suitable for the URLLC service. Upon receiving the third control message 514, the network access node 100 may determine to reconfigure the client device 100 to use the first set of parameters for radio link monitoring. Fig. 9 shows an embodiment where the network access node 300 reconfigures the radio link monitoring for the client device 100 by transmitting the previously described fourth control message 516 to the client device 100 at the time instance t7. The fourth control message 516 comprises the second reconfiguration instruction to change from the second set of parameters to the first set of parameters for performing radio link monitoring. The network access node 300 further resumes URLLC service to the client device 100.

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 together for 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 be connected to a network access node (300) over at least one radio link (602), and further being configured to

perform radio link monitoring for the radio link (602) based on a measured quality of the radio link, and at least one of a first in-synchronization threshold value and a first out-of- synchronization threshold value included in a first set of parameters;

transmit a first control message (510) to the network access node (300), wherein the first control message (510) indicates the comparison of the measured quality of the radio link (602) with at least one parameter of the second set of parameters.

2. The client device (100) according to claim 1 , configured to

compare the measured quality of the radio link (602) with at least one parameter of the second set of parameters upon the start of a timer associated with the radio link monitoring.

3. The client device (100) according to claim 2, configured to

transmit the first control message (510) to the network access node (300) upon expiry of the timer associated with the radio link monitoring.

4. The client device (100) according to any of the preceding claims, wherein the first control message (510) is a radio resource control, RRC, message or a physical uplink control channel, PUCCH, message.

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

receive a second control message (512) from the network access node (300), wherein the second control message (512) comprises a first reconfiguration instruction to change from the first set of parameters to the second set of parameters for performing radio link monitoring; perform radio link monitoring for the radio link (602) based on a measured quality of the radio link and the second set of parameters according to the first reconfiguration instruction.

6. The client device (100) according to any of the preceding claims, configured to transmit a third control message (514) to the network access node (300), wherein the third control message (514) comprises an indication that the measured quality of the radio link (602) is higher than the first in-synchronization threshold value.

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

receive a fourth control message (516) from the network access node (300), wherein the fourth control message (516) comprises a second reconfiguration instruction to change from the second set of parameters to the first set of parameters for performing radio link monitoring; perform radio link monitoring for the radio link (602) based on a measured quality of the radio link (602) and the first set of parameters according to the second reconfiguration instruction.

8. The client device (100) according to any of the preceding claims, wherein the second set of parameters is a default set of radio link parameters for performing radio link monitoring.

9. The client device (100) according to any of the preceding claims, wherein the first set of parameters is associated with an ultra-reliable low latency communication service, and the second set of parameters is associated with an enhanced mobile broadband service.

10. A network access node (300) for a wireless communication system (500), the network access node (300) being configured to be connected to a client device (100) over at least one radio link (602), and to configure the client device (100) with a first set of parameters for performing radio link monitoring for the radio link (602), the network access node (300) further being configured to

receive a first control message (510) from the client device (100), wherein the first control message (510) indicates a comparison of a measured quality of the radio link (602) with at least one parameter of a second set of parameters for performing radio link monitoring;

transmit a second control message (512) to the client device (100), wherein the second control message (512) comprises a first reconfiguration instruction instructing the client device (100) to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link (602).

1 1 . The network access node (300) according to claim 10, wherein the first set of parameters comprises a first in-synchronization threshold value and a first out-of-synchronization threshold value, and the second set of parameters comprises a second in-synchronization threshold value and a second out-of-synchronization threshold value.

12. The network access node (300) according to claim 1 1 , configured to receive a third control message (514) from the client device (100), wherein the third control message (514) comprises an indication that the measured quality of the radio link (602) is higher than the first in-synchronization threshold value;

transmit a fourth control message (516) to the client device (100), wherein the fourth control message (516) comprises a second reconfiguration instruction instructing the client device (100) to change from the second set of parameters to the first set of parameters for performing radio link monitoring for the radio link (602).

13. The network access node (300) according to any of claims 10 to 12, wherein the first control message (510) is a RRC message or a PUCCH message.

14. The network access node (300) according to any of claims 10 to 13, wherein the first set of parameters is associated with an ultra-reliable low latency communication service, and the second set of parameters is associated with an enhanced mobile broadband service.

15. A method (200) for a client device (100) being connected to a network access node 300 over at least one radio link 602, the method (200) comprising

performing (202) radio link monitoring for the radio link (602) based on a measured quality of the radio link, and at least one of a first in-synchronization threshold value and a first out-of-synchronization threshold value included in a first set of parameters;

comparing (204) the measured quality of the radio link with at least one of a second in synchronization threshold value and a second out-of-synchronization threshold value included in a second set of parameters;

transmitting (206) a first control message (510) to the network access node (300), wherein the first control message (510) indicates the comparison of the measured quality of the radio link (602) with at least one parameter of the second set of parameters.

16. A method (400) for a network access node (300) being configured to be connected to a client device (100) over at least one radio link (602), and to configure the client device (100) with a first set of parameters for performing radio link monitoring for the radio link (602), the method (400) comprising

receiving (402) a first control message (510) from the client device (100), wherein the first control message (510) indicates a comparison of a measured quality of the radio link (602) with at least one parameter of a second set of parameters for performing radio link monitoring; transmitting (404) a second control message (512) to the client device (100), wherein the second control message (512) comprises a first reconfiguration instruction instructing the client device (100) to change from the first set of parameters to the second set of parameters for performing radio link monitoring for the radio link (602).

17. A computer program with a program code for performing a method according to claim 15 or 16 when the computer program runs on a computer.