Technical Field

The disclosure relates to a client device for operation of a deactivation timer associated with a secondary serving cell. Furthermore, the disclosure also relates to corresponding methods and a computer program.

Background

The concept of Carrier Aggregation (CA) was introduced in Long Term Evolution (LTE) Release-10. CA refers to concatenation of multiple carriers which increases bandwidth and consecutively data rate of the system. LTE Release-10 supports up to 5 Component Carriers (CCs) and five bandwidth options, i.e. 1.4, 3, 5, 10 and 20 MHz.

The 5 ^th generation of cellular network or mobile network (5G) new radio (NR) supports CA up to 16 CCs. Dual Connectivity (DC) can also be supported in 5G which may support multiple carriers from different cells. A User Equipment (UE) may receive or transmit on one CC or on multiple CCs simultaneously depending on its capabilities, and CA is supported for both contiguous and non-contiguous CCs. There are three types of CA in general, i.e. intra-band contiguous, intra-band non-contiguous, and inter-band non-contiguous.

A UE capable of CA has one downlink primary CC with or without an associated uplink primary CC for primary serving cell, i.e., a PCell. In addition, it may have one or several secondary CCs for secondary serving cell, i.e., a SCell. Different UEs may have different carriers as their primary CC, i.e., the configuration of the primary CC is UE specific.

To enable reasonable UE battery consumption when CA is configured, an activation/deactivation mechanism of SCells is supported. If the UE is configured with one or more SCells, the evolved NodeB (eNodeB) or next generation nodeB (gNB) may activate or deactivate the configured SCells. Activation and deactivation do however not apply to the PCell.

After configuring/adding the SCell, as explained herein, the SCell is in deactivated state. When the SCell is modified, the UE does not change the activation status. During handover, if the same SCell is in use in the target PCell, i.e., the SCell is not released during handover, the SCell in the target cell is initially in the deactivated state. For a frequency-division duplex (FDD) system, there is no explicit activation/deactivation signaling for an uplink CCs whenever a downlink CC is activated/deactivated. The corresponding uplink CC is also activated/deactivated because of the paring of downlink and uplink CC. In order for the UE to receive data on the SCell, it has to be activated which is different from configuring the SCell. If the SCell is deactivated, the UE maintains the configuration for the SCell provided by radio resource control (RRC) signaling but it is not possible to receive either the physical downlink control channel (PDCCH) or the physical downlink shared channel (PDSCH) when the SCell is deactivated.

A typical use case of activation of the SCell is when the network configures the UE with one or more CCs but deactivates all of them except the primary CC. When there is a need for more data throughput, e.g., there is a huge amount of data to delivered to the UE in the downlink, the network can activate one or several secondary CCs to maximize the downlink throughput.

Another use case of activation of the SCell is when the PCell is fully loaded and the SCell(s) can be activated so that the data transfer can be scheduled only on the SCell, i.e. for load balancing in the system. The network can deactivate the SCell when there is no more data to be delivered to the UE and/or the channel quality of the SCell turning to be bad.

The UE and the network can deactivate an activated SCell without explicit signaling which in this case is based on a deactivation timer, i.e. the sCellDeactivationTimer. Said timer defines the amount of time, in radio frames, the UE has not received any data on the SCell. SCell activation is done via medium access control (MAC) control element (CE) whereas the deactivation mechanism is either by using MAC CE or by the expiry of the sCellDeactivationTimer. The network may configure the UE with the sCellDeactivationTimer via RRC signaling. The sCellDeactivationTimer can take values starting from 20ms to 1280ms.

If the UE receives a MAC CE in subframe #n activating the SCell, the UE shall start or restart the sCellDeactivationTimer associated with the SCell in subframe #n+8. If the UE receives PDCCH on the activated SCell indicating an uplink grant or a downlink assignment it shall restart the sCellDeactivationTimer associated with the SCell.

Similarly, if the UE receives PDCCH on the serving cell scheduling the activated SCell (cross carrier scheduling) indicating an uplink grant or a downlink assignment, the UE shall restart the sCellDeactivationTimer associated with the SCell. If the UE receives an activation/deactivation MAC CE in subframe #n deactivating the SCell or if the sCellDeactivationTimer associated with the activated SCell expires in subframe #n, the UE shall activate/deactivate the SCell no later than in subframe #n+8. The NG radio access network (RAN) configures sCellDeactivationTimer only if the UE is configured with one or more SCells. If the field is absent, the UE shall delete any existing value for this field and assume the value to be set to infinity. The UE maintains the sCellDeactivationTimer per configured SCell and deactivates the associated SCell upon its expiry. The same initial timer value applies to each instance of the sCellDeactivationTimer.

In 3GPP NR standard, a UE power saving mechanism for bandwidth adaptation are defined for CA and DC, i.e., SCell (or secondary cell group (SCG)) addition/modification/release is done by RRC control message; SCell activation/deactivation is controlled by MAC control signaling and sCellDeactivationTimer.

Summary

An objective of embodiments of the disclosure 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 disclosure can be found in the dependent claims.

According to a first aspect of the disclosure, the above mentioned and other objectives are achieved with a client device for a communication system, the client device being configured to operate in a connected mode discontinuous reception, C-DRX, and being served by at least one secondary cell; and further being configured to obtain C-DRX configuration parameters associated with a secondary serving cell; and adapt operation of a deactivation timer associated with the secondary serving cell based on the C-DRX configuration parameters.

Hence, the client device may be served by one or more primary serving cells and one or more secondary serving cells.

To adapt operation of a deactivation timer may mean that the deactivation timer is somehow manipulated, e.g. by suspending, stopping, resuming said deactivation timer. This can also imply that the value of the deactivation timer will change due to the mentioned manipulation.

An advantage of the client device according to the first aspect is that it can reduce both MAC control signaling overhead and the latency for activation or deactivation of the secondary serving cell when the client device is in C-DRX. In an implementation form of a client device according to the first aspect, adapt operation of the deactivation timer associated with the secondary serving cell comprises adapt operation of the deactivation timer based on a status of the C-DRX configuration parameters.

The status of the C-DRX configuration parameters may include the operation related to the C- DRX configuration parameters, such as stop, start, or expiry of the DRX related timers.

In an implementation form of a client device according to the first aspect, the client device is configured with a short DRX cycle, and further configured to suspend the deactivation timer when a DRX off duration starts during the short DRX cycle; and resume the deactivation timer when a DRX on duration starts during the short DRX cycle.

An advantage with this implementation form is reduced data latency by keeping the secondary serving cell(s) in active mode during a short DRX cycle in which a large amount of data may be transmitted.

In an implementation form of a client device according to the first aspect, the client device is configured to stop the deactivation timer upon switching from the short DRX cycle to a long DRX cycle.

In an implementation form of a client device according to the first aspect, the client device is configured to deactivate the secondary serving cell upon stopping the deactivation timer.

An advantage with this implementation form is improved power saving in the client device by deactivating the secondary serving cell(s) during a long DRX cycle in which data rarely may be transmitted.

In an implementation form of a client device according to the first aspect, the client device is only configured with a long DRX cycle, and further configured to stop the deactivation timer when a DRX inactivity timer expires.

In an implementation form of a client device according to the first aspect, the client device is configured to deactivate the secondary serving cell upon stopping the deactivation timer.

An advantage with this implementation form is improved power saving in the client device by deactivating the secondary serving cell(s) during a long DRX cycle in which data rarely may be transmitted.

In an implementation form of a client device according to the first aspect, wherein the deactivation timer is a secondary cell deactivation timer.

Thereby, embodiments of the disclosure can easily be implemented in LTE and NR.

In an implementation form of a client device according to the first aspect, wherein obtain the C-DRX configuration parameters comprises receive the C-DRX configuration parameters from a network access node of the communication system.

In an implementation form of a client device according to the first aspect, the C-DRX configuration parameters comprises any of: DRX Cycle, onDurationTimer, drx-lnactivityTimer, drx-Retransmission timer, shortDRX-Cycle, or drxShortCycleTimer.

According to a second aspect of the disclosure, the above mentioned and other objectives are achieved with a method for a client device configured to operate in a C-DRX and being served by at least one secondary cell; the method comprising obtaining C-DRX configuration parameters associated with a secondary serving cell; and adapting operation of a deactivation timer associated with the secondary serving cell based on the C-DRX configuration parameters.

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

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

The disclosure 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 disclosure. Further, the disclosure 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 disclosure 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 disclosure, in which:

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

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

- Fig. 3 illustrates a communication system according to an embodiment of the disclosure;

- Fig. 4 shows a timing diagram of an embodiment of the disclosure;

- Fig. 5 shows a timing diagram of an embodiment of the disclosure; and

- Fig. 6 shows a timing diagram of an embodiment of the disclosure.

Detailed Description

Previously, PCell and SCell activation and deactivation in LTE and NR was discussed. Furthermore, in order to save energy in the UE a discontinuous reception (DRX) mechanism was introduced in LTE and NR. In DRX mode the UE may go into sleep mode for a certain period of time and wake up for another period of time. In normal operation, i.e. not in DRX mode, the UE has to be awake all the time and monitor a control channel for every subframe meaning that it has to be awake all the time since the UE will not know exactly when the network will transmit data. However, if UE is always awake even when there is no data being transmitted to the UE from the network, the power consumption will be an issue.

According to a conventional solution, a MAC entity for all activated serving cells should perform C-DRX operation with a common DRX configuration. However, the inventors have realized that SCell deactivation due to the DeactivationTimer expiry in C-DRX may cause excessive MAC control signaling overhead. For example, if a short DRX cycle is configured with C-DRX mode, the DRX on duration and the DRX off duration may be frequently switched depending on the values of the C-DRX parameters and downlink and/or uplink assignment for a UE in C-DRX mode. If the DeactivationTimer expires during the DRX off duration, but the UE is scheduled after the DRX off duration, the UE should be reactivated due to the expiration of the DeactivationTimer. If data rate changes frequently, this will make the UE reactivate the SCell frequently which exhausts excessive signaling overhead with limited power saving and causes the additional latency for the SCell reactivation.

How to balance the signaling overhead and power saving should therefore also be considered according to the view of the inventors. It has been identified a tradeoff between UE power saving and data latency/throughput when the UE operates in C-DRX mode and with CA. A UE in C-DRX mode with one or more activated SCells consumes more power not only by monitoring the PDCCH on the PCell but also the PDCCH on the one or more activated SCells during the DRX on duration.

Furthermore, in C-DRX mode, SCell deactivation based on an associated timer should not be affected by DRX off duration for which the UE may not monitor the PDCCH. This requirement can make the related cell specific timer, e.g. sCellDeactivationTimer, be set to appropriate values for all UEs in RRC_CONNECTED regardless of their mode, i.e., whether or not they are in C-DRX mode. The inventors also suggest that the operation of C-DRX with short DRX cycle and long DRX cycle should also be considered to reduce MAC control signaling when activating/deactivating a SCell based on the associated timer expiration.

Therefore, the inventors propose that the operation of a deactivation timer associated with at least one secondary serving cell can be dependent on related C-DRX configuration parameters as stated herein in the present disclosure.

Fig. 1 shows a client device 100 according to an embodiment of the disclosure. 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 may be coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The client device 100 may further comprise an antenna or antenna array 110 coupled to the transceiver 104, which means that the client device 100 may be configured for wireless communications in a wireless communication system. That the client device 100 may be 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.

The client device 100 in this disclosure includes but is not limited to: a UE such as a smart phone, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having a wireless communication function, a computing device or another processing device connected to a wireless modem, an in-vehicle device, a wearable device, an integrated access and backhaul node (IAB) such as mobile car or equipment installed in a car, a drone, a device-to- device (D2D) device, a wireless camera, a mobile station, an access terminal, an user unit, a wireless communication device, a station of wireless local access network (WLAN), a wireless enabled tablet computer, a laptop-embedded equipment, an universal serial bus (USB) dongle, a wireless customer-premises equipment (CPE), and/ora chipset. In an Internet of things (IOT) scenario, the client device 100 may represent a machine or another device or chipset which performs communication with another wireless device and/or a network equipment.

The UE may further be referred to as a mobile telephone, a cellular telephone, a computer tablet or laptop with wireless capability. The UE in this context may e.g. be portable, pocket- storable, hand-held, computer-comprised, or vehicle-mounted mobile device, 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 802.11 -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 NR.

The processor 102 of the client device 100 may be referred to as one or more general-purpose central processing units (CPUs), one or more digital signal processors (DSPs), one or more application-specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs), one or more programmable logic devices, one or more discrete gates, one or more transistor logic devices, one or more discrete hardware components, and one or more chipsets.

The memory 106 of the client device 100 may be a read-only memory, a random access memory, or a non-volatile random access memory (NVRAM). The transceiver 104 of the client device 100 may be a transceiver circuit, a power controller, an antenna, or an interface which communicates with other modules or devices.

In embodiments, the transceiver 104 of the client device 100 may be a separate chipset or being integrated with the processor 102 in one chipset. While in some embodiments, the processor 102, the transceiver 104, and the memory 106 of the client device 100 are integrated in one chipset.

According to embodiments of the disclosure the client device 100 is configured to operate in a C-DRX mode and being served by at least one secondary cell. The client device 100 is further configured to obtain C-DRX configuration parameters associated with a secondary serving cell. The client device 100 is further configured to adapt operation of a deactivation timer associated with the secondary serving cell based on the C-DRX configuration 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 method 200 comprises obtaining 202 C-DRX configuration parameters associated with a secondary serving cell. The method 200 further comprises adapting 204 operation of a deactivation timer associated with the secondary serving cell based on the C-DRX configuration parameters.

Fig. 3 shows a communication system 500 according to an embodiment of the disclosure. The communication system 500 illustrates a client device 100 and a network access node 300 configured to operate in the communication system 500. For simplicity, the communication system 500 shown in Fig. 5 only comprises one client device 100 and one network access node 300. However, the 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 disclosure.

As illustrated in Fig. 3, the client device 100 may be configured to communicate with the network access node 300 in the downlink (DL) and in the uplink (UL) using control and data channels, such as PDCCH, PDSCH, physical uplink control channel (PUCCH) and physical uplink shared channel (PUSCH). The network of the communication system 500 may via the network access node 300 configure the client device 100 for different C-DRX operations e.g. as defined in 3GPP specifications. Hence, in embodiments to obtain the C-DRX configuration parameters comprises receive the C-DRX configuration parameters 510 from a network access node 300 of the communication system 500, e.g. through downlink signaling as illustrated in Fig. 3. The communication system 500 includes at least a frequency-division duplex (FDD) system and a time-division duplex (TDD) system.

In embodiments, the C-DRX configuration parameters comprises any of: DRX Cycle, onDurationTimer, drx-lnactivityTimer, drx-Retransmission timer, shortDRX-Cycle, or drxShortCycleTimer. Hence, the client device 100 will adapt its operation of the deactivation timer associated with one or more secondary serving cells based on mentioned C-DRX configuration parameters.

In NR the network decides when to let a UE sleep and when to wake up the UE and inform the timing to the UE using RRC messages. The network informs the UE of the DRX timing using RRC ConnectionReconfiguration or RRC Connection Setup. Table 1 below shows the meaning of each DRX parameter.

Table 1

Some typical use cases when the UE is in DRX mode include:

1 . Only long DRX cycle is configured and no PDCCH is received during the cycle. 2. Only long DRX cycle is configured and a PDCCH is received during a cycle.

3. Only long DRX cycle is configured and a PDCCH and DRX command MAC CE are received during a cycle.

4. Both long DRX cycle and short DRX cycle are configured and no PDCCH is received during the cycle. This may be the most complicated case related to DRX cycle. The overall logic goes like this: i. when C DRX is configured and the last DCI arrived, ii. drx-lnactivityTimer starts/restart and 'Wake-up status' continues until the drx- InactivityTimer expires, iii. after drx-lnactivityTimer expired and the shortDRX-Cycle condition meet, the shortDRX-Cycle starts and drxShortCycleTimer starts, iv. if there is no downlink control information (DCI), e.g. no PDCCH, until drxShortCycleTimer expires and then long Drx cycle starts, and v. if a DCI arrives during the wake-up period of any DRX cycle, go to step ii).

Moreover, for providing even deeper understanding of embodiments of the disclosure Figs. 4 to 6 illustrates different embodiments set in a NR context hence the terminology and expressions used in these sections. For example, the deactivation timer is a sCellDeactivationTimer, and the client device 100 is a UE in these examples. However, embodiments of the disclosure are not limited thereto.

Further, the upper timeline in Figs. 4 to 6 illustrates the C-DRX configuration of the client device/UE 100. The lower timeline in Figs. 4 to 6 illustrates the CA set up and operation of the sCellDeactivationTimer, i.e. the deactivation timer, in relation to the C-DRX configuration parameters.

Fig. 4 illustrates a general embodiment for adapting operation of the deactivation timer (i.e. sCellDeactivationTimer in NR) associated with at least one secondary serving cell (i.e. SCell in NR). Fig.4 shows a solution for the operation the sCellDeactivationTimer regardless of the client device 100 is configured with short DRX cycle or not.

According to this embodiment if a DRX off duration starts, e.g. when the drx-lnactivityTimer expires, the sCellDeactivationTimer is suspended if the sCellDeactivationTimer is running. Further, the sCellDeactivationTimer is resumed when the DRX on duration starts if the sCellDeactivationTimer is suspended, e.g., when the drx-OnDurationTimer starts at the beginning of the next DRX cycle. In step I at time instance to in Fig. 4, there is data to be transmitted and/or received to and/or from the UE which is illustrated with the dashed block on the upper timeline. Hence the UE is in active state and a PCell serving the UE is activated.

In step II at time instance t1 in Fig. 4, at least one SCell is activated and serves the UE. The SCell can be activated though predefined control signaling, e.g. using MAC CE, as previously discussed.

In step III at time instance t2 in Fig. 4, the sCellDeactivationTimer is started according to predefined rules, e.g. given by communication specifications or standards.

In step IV at time instance t3 in Fig. 4, the drx-lnactivityTimer expires (see upper timeline) which means that the sCellDeactivationTimer is suspended. The time between time t3 and t4 is a so called DRX off duration.

In step V at time instance t4 in Fig. 4, the UE wakes up since the drx-OnDurationTimer starts. Therefore, the sCellDeactivationTimer is resumed.

Possible non-limiting suggestion of proposed operation of activation/deactivation of SCells are as below:

The MAC entity shall for each configured SCell:

1 > DRX is configured:

2> If the drx-lnactivityTimer expires and the sCellDeactivationTimer is running:

3> suspend the sCellDeactivationTimer associated with the SCell.

2> if the drx-OnDurationTimer starts and the sCellDeactivationTimer is being suspended

3> resume the suspended sCellDeactivationTimer associated with the SCell.

In Fig. 5 embodiments considering both short DRX cycles and long DRX cycles is illustrated which is adaptation of bandwidth in C-DRX when the UE is configured with short DRX cycle.

According to this embodiment, during short DRX cycle, the sCellDeactivationTimer is suspended and resumed based on DRX off duration and DRX on duration start. Further, during long DRX cycle, the sCellDeactivationTimer is stopped and the secondary serving cell(s) is deactivated. This embodiment may be stated as:

• If the DRX OFF duration starts, e.g., the drx-lnactivityTimer expires: o start or restart the drx-ShortCycleTimer; and o suspend the sCellDeactivationTimer if the sCellDeactivationTimer is running;

• If the DRX ON duration starts, e.g., the drx-OnDurationTimer starts, etc., and the drx- ShortCycleTimer is running: o resume the sCellDeactivationTimer if the sCellDeactivationTimer is running;

• If drx-ShortCycleTimer expires: o stop the sCellDeactivationTimer if the sCellDeactivationTimer is running, o deactivate any activated secondary serving cells, and o use the long DRX cycle.

In step I at time instance to in Fig. 5, there is data to be transmitted and/or received to and/or from the UE and hence the UE is in active state and a PCell serving the UE is activated.

In step II at time instance t1 in Fig. 5, at least one SCell is activated. The SCell can be activated though control signaling, e.g. using MAC CE, as previously described.

In step III at time instance t2 in Fig. 5, the drx-lnactivityTimer expires and the sCellDeactivationTimer is therefore suspended.

In step IV at time instance t3 in Fig. 5, the UE is configured with short DRX cycle and the drx- ShortCycleTimer starts running. The sCellDeactivationTimer is resumed. During the time period the UE is configured with short DRX cycle, the sCellDeactivationTimer is resumed when a DRX on duration starts and suspended when a DRX on duration ends. In other words, the UE 100 is configured to suspend the deactivation timer when a DRX off duration starts during the short DRX cycle; and resume the deactivation timer when a DRX on duration starts during the short DRX cycle.

In step V at time instance t4 in Fig. 5, the drx-ShortCycleTimer expires and the UE is thereafter configured with long DRX cycle. When the drx-ShortCycleTimer expires the sCellDeactivationTimer is stopped at time instance t4.

In step VI in Fig. 5, upon stopping the sCellDeactivationTimer the SCell(s) is deactivated which means that only the PCell is active. In other words, the UE 100 is configured to stop the deactivation timer upon switching from the short DRX cycle to a long DRX cycle, and further configured to deactivate the secondary serving cell upon stopping the deactivation timer. When the UE is configured with long DRX cycle the UE wakes up at each DRX on duration and is served by the PCell. Possible non-limiting suggestion of proposed operation may be:

1 > if drx-lnactivityTimer expires or a DRX Command MAC CE is received:

2> if the Short DRX cycle is configured:

3> start or restart drx-ShortCycleTimer in the first symbol after the expiry of drx- lnactivityTimer or in the first symbol after the end of DRX Command MAC CE reception;

3> use the Short DRX Cycle.

3> If sCellDeactivationTimer is running:

4> suspend the sCellDeactivationTimer associated with the SCell.

2>else:

3> use the Long DRX cycle.

1 > if the drx-OnDurationTimer starts:

2> if drx-ShortCycleTimer is running:

3> if sCellDeactivationTimer is being suspended:

4> resume the suspended sCellDeactivationTimer associated with the

SCell.

1 > if drx-ShortCycleTimer expires:

2>use the Long DRX cycle.

2>stop sCellDeactivationTimer if it is running

2> deactivate the SCell associated with the sCellDeactivationTimer.

1> if a Long DRX Command MAC CE is received:

2 > stop drx-ShortCycleTimer,

2>use the Long DRX cycle.

2>stop sCellDeactivationTimer if it is running

2> deactivate the SCell associated with the sCellDeactivationTimer.

An alternative solution when the short DRX cycle is configured is also proposed. In order not to deactivate any active secondary serving cells during the short DRX cycle period, the sCellDeactivationTimer can be set to an infinite value when the C-DRX with short DRX cycle is configured. In this case, if the secondary serving cells is activated for a UE in C-DRX mode by the secondary serving cells activation/deactivation MAC CE during DRX on duration, the secondary serving cells can be deactivated only by secondary serving cells activation/deactivation MAC CE. For this case, the following non-limiting operation may be:

The MAC entity shall for each configured SCell:

1 > DRX with Short DRX cycle is configured:

2> sCellDeactivationTimer is set to infinity. In Fig. 6, the operation of the sCellDeactivationTimer when the UE is not configured with short DRX cycle but only configured with long DRX cycle is considered and illustrated. According to this embodiment, if a DRX off duration starts, e.g. the drx-lnactivityTimer expires, the UE stops the sCellDeactivationTimer if any of them is running, and thereafter deactivates any activated secondary serving cells. In other words, the UE is configured to stop the deactivation timer when a DRX inactivity timer expires, and to deactivate the secondary serving cell upon stopping the deactivation timer.

In step I at time instance to in Fig. 6, there is data to be transmitted and/or received to and/or from the UE which is illustrated with the dashed block on the upper C-DRX drawing. Hence the UE is active and a PCell serving the UE is activated.

In step II at time instance t1 in Fig. 6, at least one SCell is activated. The SCell can be activated though control signaling e.g. using MAC CE.

In step III at time instance t2 in Fig. 6, the sCellDeactivationTimer is started according to predefined rules.

In step IV at time instance t3 in Fig. 6, when the drx-lnactivityTimer expires the sCellDeactivationTimer is stopped.

In step V in Fig. 6, upon stopping the sCellDeactivationTimer the SCell(s) is deactivated which means that only the PCell is active. When the UE is configured with long DRX cycle the UE wakes up at each DRX on duration and is served by the PCell.

In step VI at time instance t4, the UE wakes up and is served by the PCell and this process is continued.

Possible non-limiting suggestion of proposed operation may be:

When DRX is configured, the MAC entity shall:

1 > if drx-lnactivityTimer expires or a DRX Command MAC CE is received:

2> if the Short DRX cycle is configured:

3> start or restart drx-ShortCycleTimer in the first symbol after the expiry of drx- lnactivityTimer or in the first symbol after the end of DRX Command MAC CE reception;

3> use the Short DRX Cycle.

2> else: 3> use the Long DRX cycle.

3> If the drx-lnactivityTimer expires and an sCellDeactivationTimer is running:

4> stop the sCellDeactivationTimer; and

4> deactivate the SCell.

In an alternative solution, the value of sCellDeactivationTimer can be set differently for C-DRX from non-DRX, i.e., set to infinity for C-DRX and set to a finite value for non-DRX. The latency to activate a SCell may be around 28ms or 48ms depending on various scenarios, which is too large to adapt the bandwidth dynamically for the client device 100 in C-DRX. If sCellDeactivationTimer is set to infinity for C-DRX, timer based SCell deactivation is not used, and only MAC CE is used to deactivate an activated SCell if needed when a client device 100 is in C-DRX.

Furthermore, any method according to embodiments of the disclosure 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 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 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 disclosure is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.