Patent Description:
In <NUM> new radio (<NUM>-NR) there are three radio resource control (RRC) states for a user equipment (UE). The RRC states defined in <NUM>-NR are RRC_IDLE, RRC_INACTIVE and RRC_CONNECTED. In each of these RRC states discontinuous reception (DRX) can be utilized to decrease the energy consumption of the UE. When the UE is in RRC_IDLE state or RRC_INACTIVE state, DRX allows the UE to go into a sleep state between paging occasions. When the UE is in RRC_CONNECTED state, the network can parameterise the UE to allow DRX to be used between data transmissions.

<CIT> relates to wireless communications and, more particularly, to configuration of reference signals for beam refinement, based on DRX parameters. It is described that, for example, a method of wireless communications by a base station may include determining a reference signal configuration for a user equipment (UE) based, at least in part, on one or more discontinuous reception (DRX) parameters, and signaling the reference signal configuration and the one or more DRX parameters to the UE.

<CIT> describes a method and apparatus for transmitting a physical random access channel (PRACH) in a wireless communication system. It is described that a user equipment (UE) receives multiple PRACH configurations which include a first PRACH configuration for new radio access technology (NR) downlink/uplink (DL/UL) carrier in a NR band and a second PRACH configuration for a supplemental UL carrier in a long-term evolution (LTE) band, and transmits at least one of a first PRACH for accessing the NR DL/UL carrier in the NL band by using a first PRACH power based on the first PRACH configuration, or a second PRACH for accessing the supplemental UL carrier in the LTE band by using a second PRACH power based on the second PRACH configuration. It is described that the first PRACH configuration and the second PRACH configuration include different PRACH power configurations.

<NPL>, describes that the document provides an overview and overall description of the NG-RAN and focuses on the radio interface protocol architecture of NR connected to 5GC (E-UTRA connected to 5GC is covered in the <NUM> series).

In long term evolution (LTE), wake-up signalling is currently being standardized. Hence, it is highly likely that wake-up signalling will be adopted in <NUM>-NR standards as well. Wake-up signalling can be used by the network to instruct a UE in a sleep state to continue to sleep or to wake-up to receive upcoming control information and data transmission.

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.

Appended claim <NUM> defines a client device. Appended claim <NUM> defines a network access node. Appended claim <NUM> defines a method for a client device. Appended claim <NUM> defines a method for a network access node. Appended claim <NUM> defines a computer program. Appended claim <NUM> defines a computer program. The invention and its scope of protection is defined by these independent claims.

In the following, implementations not falling within the scope of the claims are to be understood as examples useful for understanding the application.

A serving beam configuration can in this disclosure be understood to mean a configuration defining the serving beams to be used by the network access node to serve the client device. That the client device is in connected state can in this disclosure be understood to mean that the client device has an established connection with a network access node. That the client device is in the power saving state can in this disclosure be understood to mean that the client device does not have an established connection with a network access node or that its connection has been suspended. In the power saving state the client device may have turned one or more of its transceivers partially or fully off. The power saving state can be a so-called sleep state.

An advantage of the client device according to the invention is that the network can reach the client with low latency, and at the same time the client device saves energy e.g. compared to when being in a connected state.

A further advantage is that the network increases the capacity of paging messages, and the client is reachable with low latency while saving energy. The capacity can be considered as the radio resources used for paging.

A further advantage is that the network can maintain reachability to the client device.

A further advantage is that the network can associate the serving beam to the client device corresponding to the I-RNTI.

A further advantage is that the client device is acknowledged of the updated serving beams.

A further advantage is that the network can maintain reachability to the client device while the latter is in a power saving state.

A further advantage is that the client device can save energy by only monitoring the serving beams. Furthermore, an updating mechanism is provided so to solve a beam failure detected by the client device.

An advantage of the network access node is that the network can reach the client with low latency, and at the same time the client device can save energy.

A further advantage is that the network can increase the capacity of the paging messages.

A further advantage is that the network can maintain reachability to the client device while the latter is in power saving state.

A further advantage is that the network access node acknowledges the update of the serving beams.

A further advantage is that the network access node can maintain reachability to the client device while allowing the client device to save energy by focusing on monitoring the serving beams.

Beam management is a distinguishing feature of <NUM>-NR. In LTE, which does not consider beam management, wake-up signalling for waking up UEs in RRC_IDLE state is being standardized. The aim is to have a wake-up signal indicating whether a UE is required to wake-up for upcoming paging occasion or not. Also wake-up signal for connected state DRX has been discussed.

In <NUM>-NR beam management is based on synchronization signal blocks (SSBs) and channel state information reference signals (CSI-RSs). Hence, in addition to cell level mobility also beam level mobility is considered in RRC_CONNECTED state. However, in RRC_IDLE state or RRC_INACTIVE state beam level mobility is not considered. In multi-beam operation, paging can be sent with multiple beams to increase the chance of reaching the UE. In this case, each beam has its own synchronization signal (SS) and physical broadcast channel (PBCH) block. These SS/PBCH blocks are transmitted in bursts by the network. The periodicity of the bursts can be configured and can be between <NUM> and <NUM>. By receiving and measuring such bursts, the UE can determine the serving beam(s).

To improve energy efficiency, wake-up signalling may be introduced for <NUM>-NR. Moreover, the inventors have identified that it could be beneficial to considered beam level mobility in at least RRC_INACTIVE state in addition to RRC_CONNECTED state. This could improve wake-up signalling reachability and radio resource efficiency.

Hence, embodiments of the invention provide ways to manage beams for UEs in power saving state, such as RRC_INACTIVE state or RRC_IDLE state. Thereby, energy efficiency can be improved, while still maintain wake-up signalling and paging reachability for UEs in power saving state.

<FIG> shows a client device <NUM> according to an embodiment of the invention. In the embodiment shown in <FIG>, the client device <NUM> comprises a processor <NUM>, a transceiver <NUM> and a memory <NUM>. The processor <NUM> is coupled to the transceiver <NUM> and the memory <NUM> by communication means <NUM> known in the art. The client device <NUM> further comprises an antenna or antenna array <NUM> coupled to the transceiver <NUM>, which means that the client device <NUM> is configured for wireless communications in a wireless communication system.

That the client device <NUM> is configured to perform certain actions can in this disclosure be understood to mean that the client device <NUM> comprises suitable means, such as e.g. the processor <NUM> and the transceiver <NUM>, configured to perform said actions.

According to embodiments of the invention the client device <NUM> is configured to obtain a serving beam configuration when being in a connected state. The serving beam configuration indicates one or more serving beams to be monitored by the client device <NUM> when being in a power saving state. The client device <NUM> is further configured to monitor the one or more serving beams of a network access node <NUM> (shown in <FIG>) according to the serving beam configuration when being in the power saving state. Upon detecting a beam failure for the one or more monitored serving beams when being in the power saving state, the client device <NUM> is configured to perform a beam reconfiguration procedure.

<FIG> shows a flow chart of a corresponding method <NUM> which may be executed in a client device <NUM>, such as the one shown in <FIG>. The method <NUM> comprises obtaining <NUM> a serving beam configuration when being in a connected state. The serving beam configuration indicates one or more serving beams to be monitored by the client device <NUM> when being in a power saving state. The method <NUM> further comprises monitoring <NUM> the one or more serving beams of a network access node <NUM> according to the serving beam configuration when being in the power saving state. Furthermore, the method <NUM> comprises performing <NUM> a beam reconfiguration procedure upon detecting a beam failure for the one or more monitored serving beams when being in the power saving state.

<FIG> shows a network access node <NUM> according to an embodiment of the invention. In the embodiment shown in <FIG>, the network access node <NUM> comprises a processor <NUM>, a transceiver <NUM> and a memory <NUM>. The processor <NUM> is coupled to the transceiver <NUM> and the memory <NUM> by communication means <NUM> known in the art. The network access node <NUM> may be configured for both wireless and wired communications in wireless and wired communication systems, respectively. The wireless communication capability is provided with an antenna or antenna array <NUM> coupled to the transceiver <NUM>, while the wired communication capability is provided with a wired communication interface <NUM> coupled to the transceiver <NUM>.

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

According to embodiments of the invention the network access node <NUM> is configured to obtain a serving beam configuration for a client device <NUM>. The serving beam configuration indicates one or more serving beams to be monitored by the client device <NUM> when the client device <NUM> is in a power saving state. The network access node <NUM> is further configured to transmit a reference signal in each one of the one or more serving beams to the client device <NUM> when the client device <NUM> is in the power saving state.

<FIG> shows a flow chart of a corresponding method <NUM> which may be executed in a network access node <NUM>, such as the one shown in <FIG>. The method <NUM> comprises obtaining <NUM> a serving beam configuration for a client device <NUM>. The serving beam configuration indicates one or more serving beams to be monitored by the client device <NUM> when the client device <NUM> is in a power saving state. The method <NUM> further comprises transmitting <NUM> a reference signal in each one of the one or more serving beams to the client device <NUM> when the client device <NUM> is in the power saving state.

<FIG> shows a wireless communication system <NUM> according to an implementation. The wireless communication system <NUM> comprises a client device <NUM> and a network access node <NUM> configured to operate in the wireless communication system <NUM>. For simplicity, the wireless communication system <NUM> shown in <FIG> only comprises one client device <NUM> and one network access node <NUM>. However, the wireless communication system <NUM> may comprise any number of client devices <NUM> and any number of network access nodes <NUM> without deviating from the scope of the invention.

In the wireless communication system <NUM>, the client device <NUM> can be in a connected state or in a power saving state. In the connected state, the client device has an established connection with a network access node, e.g. the network access node <NUM> shown in <FIG>. In the power saving state, the client device does not have a connection with any network access node or its connection have been suspended. In the power saving state the client device <NUM> may have turned one or more of its transceivers partially of fully off. The power saving state can e.g. be a RRC_INACTIVE state or a RRC_IDLE state.

When the client device <NUM> is in the connected state, the client device <NUM> obtains a serving beam configuration indicating one or more serving beams to be monitored by the client device <NUM> when being in the power saving state. The serving beam configuration for the power saving state may be specific for beam monitoring in the power saving state or may be the same as a serving beam configuration used by the client device <NUM> when being in the connected state. In the embodiment shown in <FIG>, the client device <NUM> is assumed to have obtained a serving beam configuration indicating three serving beams <NUM>, <NUM>, <NUM> to be monitored by the client device <NUM> when the client device <NUM> is in the power saving state. The network access node <NUM> transmit a reference signal in each one of the three serving beams <NUM>, <NUM>, <NUM> to the client device <NUM> and the client device <NUM> monitors the three serving beams <NUM>, <NUM>, <NUM> transmitted from a network access node <NUM> when the client device <NUM> is in the power saving state. The serving beam configuration may in embodiments be received from the network access node <NUM>, as will now be described with reference to <FIG>.

<FIG> shows signalling and interworking between a network access node <NUM> and a client device <NUM> according to embodiments of the invention. In step I in <FIG>, the network access node <NUM> transmits a serving beam configuration <NUM> to the client device <NUM> when the client device <NUM> is in connected state. The serving beam configuration <NUM> indicates one or more serving beams to be monitored by the client device <NUM> when the client device <NUM> is in the power saving state. The network access node <NUM> obtains the serving beam configuration for the client device <NUM> by determining the serving beam configuration or by obtaining the serving beam configuration from e.g. another network node. In embodiments where the network access node <NUM> determines the serving beam configuration, the network access node <NUM> may e.g. determine the serving beam configuration based on downlink measurements performed by and received periodically from the client device <NUM>. The serving beam configuration can be signalled in a control channel to the client device <NUM>, e.g. in a PDCCH.

The client device <NUM> receives the serving beam configuration <NUM> from the network access node <NUM>. The serving beam configuration <NUM> is transmitted by the network access node <NUM> and received by the client device <NUM>, when the client device <NUM> is in the connected state. In step II in <FIG>, the state of the client device <NUM> changes from the connected state to the power saving state. The state change may e.g. be triggered by a state change request from the network access node <NUM>, as known in the art.

When the client device <NUM> is in the power saving state, the network access node <NUM> transmits reference signals RSs to the client device <NUM>, as shown in step III in <FIG>. The network access node <NUM> transmits one or more reference signals in each one of the one or more serving beams indicated in the serving beam configuration <NUM>. The reference signals RSs may e.g. be SSBs and/or CSI-RSs and may be transmitted periodically. Each reference signal is associated with a specific serving beam according to embodiments of the invention.

In step IV in <FIG>, the client device <NUM> in the power saving state monitors the one or more serving beams transmitted from a network access node <NUM> based on the received reference signals RSs from the network access node <NUM>. Upon detecting a beam failure for the one or more monitored serving beams, the client device <NUM> performs a beam reconfiguration procedure in step V in <FIG>. The beam reconfiguration procedure may comprise the client device <NUM> selecting a candidate beam and initiate a random access procedure to restore beam synchronization with the network access node <NUM>, as will now be described with reference to <FIG>.

<FIG> shows a beam reconfiguration procedure according to an embodiment of the invention.

The beam reconfiguration procedure is performed by a client device <NUM> in power saving state and is triggered when a beam failure is detected, as described with reference to <FIG>. Hence, step I in <FIG> is performed when the client device <NUM> in the power saving state detects a beam failure for the one or more monitored serving beams. In step I in <FIG>, the client device <NUM> selects at least one candidate beam. The client device <NUM> further transmits a random access preamble <NUM> associated with the selected candidate beam to the network access node <NUM>, as shown in step II in <FIG>. The selection of candidate beams can be performed in a number of different ways. In a non-limiting example the client device <NUM> measures all beams from the network and selects one or more of the beams with the highest quality or with a quality above a predefined threshold. The quality mentioned herein can e.g. correspond to a measured SINR value or a received signal strength.

When the network access node <NUM> receives the random access preamble <NUM> associated with the candidate beam from the client device <NUM> the network access node <NUM> transmits a random access response <NUM> to the client device <NUM> in response to the reception of the random access preamble <NUM>, as shown in step III in <FIG>. Upon reception of the random access response <NUM> from the network access node <NUM>, the client device <NUM> transmits a connection resume request <NUM> to the network access node <NUM>, as shown in step IV in <FIG>. The connection resume request <NUM> may e.g. be a RRC connection resume request.

The connection resume request <NUM> may comprise different information depending on whether the selected candidate beam is within a current radio access network notification area (RNA) of the client device <NUM> or not. When the selected candidate beam is within the current RNA of the client device <NUM>, the connection resume request <NUM> may indicate a serving beam configuration update request for the power saving state. On the other hand, when the selected candidate beam is outside the current RNA of the client device <NUM>, the connection resume request <NUM> may further indicate a RNA update request. Normally, the network access node <NUM> thereafter transmits a RRC connection release/resume message to the client device <NUM>.

When the network access node <NUM> receive a connection resume request <NUM> from the client device <NUM>, where the connection resume request <NUM> further indicates a serving beam update request for the power saving state, when the candidate beam is within a current RNA of the client device <NUM>, the network access node <NUM> may update the serving beam configuration for the client device <NUM>. The network access node <NUM> further transmits the updated serving beam configuration to the client device <NUM> (not shown in <FIG>). Hence, in response to the transmission of the connection resume request <NUM>, the client device <NUM> may receive an updated serving beam configuration from the network access node <NUM>, where the updated serving beam configuration indicates one or more updated serving beams to be monitored by the client device <NUM> when being in the power saving state. In this case, the client device <NUM> monitors the one or more updated serving beams according to the updated serving beam configuration when being in the power saving state. Hence, an updating mechanism in respect of the serving beam configuration is provided.

In step V in <FIG>, the network access node <NUM> transmits a connection release 670a or a connection resume 670b, in response to the connection resume request <NUM>. For example, when the network access node <NUM> receive a connection resume request <NUM> indicating a serving beam update request, the network access node <NUM> may initiate the update of the serving beam configuration and transmit a connection release 670a to the client device <NUM>, if no other data transmission with the client device <NUM> is pending. In this case, the client device <NUM> returns to the power saving state, where the client device <NUM> monitors the one or more updated serving beams according to the updated serving beam configuration. A connection resume 670b may e.g. be transmitted if further data transmission with the client device <NUM> is pending.

In embodiments of the invention, the client device <NUM> uses an inactive radio network temporary identifier (I-RNTI) to inform the network access node <NUM> about the selected candidate beam. In this way, the client device <NUM> may perform the beam reconfiguration procedure during the power saving state. <FIG> shows an embodiment where a beam reconfiguration procedure is performed based on a I-RNTI.

Step I and step II in <FIG> corresponds to step I and step II in <FIG>, respectively. In other words, the client device <NUM> selects at least one candidate beam in step I in <FIG> and transmits a random access preamble <NUM> associated with the selected candidate beam to the network access node <NUM> in step II in <FIG>. The client device <NUM> further transmits an I-RNTI of the client device <NUM> to the network access node <NUM> upon transmitting the random access preamble <NUM>, as shown in step III in <FIG>. Although shown as a separate step in <FIG>, the I-RNTI may in embodiments not being part of the invention be transmitted together with the random access preamble <NUM>.

For example, the client device <NUM> may transmit one message comprising both the random access preamble <NUM> and the I-RNTI.

The network access node <NUM> receives the I-RNTI of the client device <NUM> from the client device <NUM> upon reception of the random access preamble <NUM> from the client device <NUM> and identifies the client device <NUM> based on the I-RNTI of the client device <NUM>. Based on the received random access preamble <NUM> associated with the selected candidate beam, the network access node <NUM> may update the serving beam configuration for the client device <NUM>. and transmit the updated serving beam configuration to the client device <NUM> (not shown in <FIG>). In an alternative the network access node <NUM> may transmit an acknowledge message to the client device <NUM> in response to the random access preamble <NUM>.

The network access node <NUM> transmits a response message <NUM> to the client device <NUM>, as shown in step IV in <FIG>, when the client device <NUM> is in the power saving state. The response message <NUM> is addressed to the I-RNTI of the client device <NUM>. Hence, the client device <NUM> receives the response message <NUM> from the network access node <NUM> in response to the transmission of the I-RNTI of the client device <NUM> when the client device <NUM> is in the power saving state, where the response message <NUM> is addressed to the I-RNTI of the client device <NUM>. The response message <NUM> may be used for acknowledging the serving beam update and may in embodiments be a paging message addressed to the I-RNTI of the client device <NUM>.

Furthermore, in embodiments of the invention the random access preamble <NUM> may comprise a preamble sequence which is dedicated to the client device <NUM> e.g. by the network access node <NUM>. The client device <NUM> may be informed about the dedicated preamble sequence when being in connected state. In this case the I-RNTI can be excluded, since the client device <NUM> can be identified based on the dedicated preamble sequence. In further embodiments, a special cause value for the random access may be assigned for the beam reconfiguration procedure, i.e. to initiate a serving beam update procedure. By using dedicated preamble sequences or a special random access cause value for the beam reconfiguration procedure the signalling between the network access node <NUM> and the client device <NUM> can be reduced. However, with the beam reconfiguration procedure based on I-RNTI the response message <NUM> addressed to the client device <NUM> can be used for acknowledgement, thereby increasing the reliability.

<FIG> shows a method <NUM> for beam management of a client device <NUM> in the power saving state. In step <NUM>, the client device <NUM> monitors one or more serving beams transmitted from a network access node <NUM> according to a serving beam configuration when being in the power saving state. As previously described, the client device <NUM> obtains the serving beam configuration e.g. from the network access node <NUM>. The monitoring in step <NUM> may comprise the client device <NUM> determining a quality of each serving beam indicated in the serving beam configuration. The quality of each serving beam may be determined based on measurements of reference signals, such as e.g. SSBs or CSI-RSs, associated with each serving beam.

In step <NUM>, the quality of each serving beam is compared to a quality threshold value, to determine whether the quality of each serving beam is below the quality threshold value or not. When the determined quality of all serving beams are below the quality threshold value, i.e. the outcome of the determination in step <NUM> is YES, the client device <NUM> detects a beam failure and moves to step <NUM>. On the other hand, when the determined quality of a serving beam is above the quality threshold value, i.e. the outcome of the determination in step <NUM> is NO, the client device <NUM> continues to monitor the one or more serving beams in step <NUM>. Generally, it is not considered a beam failure if the quality of at least one of the serving beams is over the quality threshold value.

Upon detecting the beam failure for the one or more monitored serving beams in step <NUM>, the client device <NUM> evaluates possible candidate beams in step <NUM>. Step <NUM> may comprise the client device <NUM> evaluating the quality of one or more candidate beams to find at least one suitable candidate beam to select from the one or more evaluated candidate beams. In step <NUM>, the client device <NUM> determines whether a candidate beam was selected or not. If the client device <NUM> cannot find a suitable candidate beam to select after a certain time, the client device <NUM> performs step <NUM>, where the client device <NUM> enters an idle state. Step <NUM> may e.g. be performed if an inactivity timer expires before a suitable candidate beam has been found. For example, when the power saving state is an inactivity state, the client device <NUM> may enter an idle state when no candidate beam has been selected upon detecting a beam failure for the one or more monitored serving beams and when an inactivity timer associated with the one or more monitored serving beams has expired. The candidate beam is a beam which is not a beam belonging to the set of serving beams.

If a candidate beam is selected, the client device <NUM> determines in step <NUM> whether the selected candidate beam belongs to the same RAN as the one or more serving beams or not. When the selected candidate beam belongs to the same RAN as the one or more serving beams, i.e. the outcome of the determination in step <NUM> is YES, the client device <NUM> transmits a connection resume request <NUM> indicating a serving beam configuration update request for the power saving state in step <NUM>, as described with reference to <FIG>. Step <NUM> comprises the client device <NUM> transmitting a random access preamble <NUM> and a I-RNTI of the client device <NUM>, as described with reference to <FIG>. On the other hand, when the selected candidate beam belongs to a different RAN than the one or more serving beams, i.e. the outcome of the determination in step <NUM> is NO, the client device <NUM> transmits a connection resume request <NUM> indicating indicates a RNA update request in step <NUM>.

By using the serving beam monitoring in power saving state and beam reconfiguration procedure according to embodiments of the invention, the network access node <NUM> is aware of the serving beams the network access node <NUM> can use to reach the client device <NUM>, when the client device <NUM> is in the power saving state. Thereby, the network access node <NUM> can reach or wake-up the client device <NUM> rapidly and without wasting radio resources. For example, the network access node <NUM> may page the client device <NUM> only in the one or more serving beams, instead of paging the client device <NUM> within the whole RAN.

According to embodiments of the invention, the client device <NUM> hence monitors for a paging message <NUM> in the one or more serving beams when being in the power saving state. If the network access node <NUM> want to reach the client device <NUM>, the network access node <NUM> may transmit a paging message <NUM> to the client device <NUM> in the one or more serving beams, monitored by the client device <NUM>, when the client device <NUM> is in the power saving state.

In a similar way, wake-up signalling may be performed based on the one or more serving beams monitored by the client device <NUM> in the power saving state. In embodiments, the client device <NUM> is configured with a wake-up signalling configuration based on which the client device <NUM> monitors wake-up signals.

According to embodiments of the invention the client device <NUM> obtains a wake-up signalling configuration when being in the connected state. The wake-up signalling configuration indicates wake-up signals to be monitored by the client device <NUM> on the one or more serving beams when being in the power saving state. The client device <NUM> may e.g. receive the wake-up signalling configuration from the network access node <NUM>. In this case, the network access node <NUM> may determine the wake-up signalling configuration for the client device <NUM> when the client device <NUM> is in the power saving state and transmit the wake-up signalling configuration to the client device <NUM>.

When being in the power saving state, the client device <NUM> monitors wake-up signals <NUM> in the one or more serving beams according to the wake-up signalling configuration. If the network access node <NUM> want to wake-up the client device <NUM>, the network access node <NUM> transmits wake-up signals <NUM> in the one or more serving beams to the client device <NUM> when the client device <NUM> is in the power saving state.

The client device <NUM> herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (IoT) 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 <NUM>-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 <NUM> 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 <NUM>-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 (<NUM>) wireless systems.

Moreover, it is realized by the skilled person that embodiments of the client device <NUM> and the network access node <NUM> 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 <NUM> and the network access node <NUM> 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.

Claim 1:
A client device (<NUM>) for a wireless communication system (<NUM>), the client device (<NUM>) being configured to
obtain a serving beam configuration when being in a connected state, wherein the serving beam configuration indicates one or more serving beams to be monitored by the client device (<NUM>) when being in a power saving state;
monitor the one or more serving beams of a network access node (<NUM>) according to the serving beam configuration when being in the power saving state;
perform a beam reconfiguration procedure upon detecting a beam failure for the one or more monitored serving beams when being in the power saving state; wherein
the client device is further configured to
select a candidate beam upon detecting the beam failure for the one or more monitored serving beams;
transmit a random access preamble (<NUM>) associated with the selected candidate beam;
transmit an inactive radio network temporary identifier, I-RNTI, of the client device (<NUM>) upon transmitting the random access preamble (<NUM>).