WO2022021096A1

WO2022021096A1 - Methods for communication, terminal device, network device and computer-readable media

Info

Publication number: WO2022021096A1
Application number: PCT/CN2020/105302
Authority: WO
Inventors: Da Wang; Gang Wang
Original assignee: Nec Corporation
Priority date: 2020-07-28
Filing date: 2020-07-28
Publication date: 2022-02-03

Abstract

Embodiments of the present disclosure relate to methods for communication, terminal device, network device and computer readable media. In the method, in response to a failure of a link between a terminal device and the first network device, the terminal device enables transmission on at least one cell of a deactivated cell group of the second network device serving the terminal device. Then, the terminal device transmits information concerning the failure to the second network device on the at least one cell. With the above solution, a solution on fast MCG link recovery in case of the SCG deactivated is provided, thereby improving the rate of success of MCG link recovery.

Description

METHODS FOR COMMUNICATION, TERMINAL DEVICE, NETWORK DEVICE AND COMPUTER-READABLE MEDIA

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to methods for communication, terminal device, network device and computer readable media.

BACKGROUND

Dual connectivity (DC) is a mode of operation in which a terminal device (for example, user equipment, UE) can be configured to utilize radio resources provided by two network devices (for example, two base stations) . One network device serves the terminal device as a master node (MN) , and another network device serves the terminal device as a secondary node (SN) . The MN and SN are connected via a non-ideal back-haul over a network interface and at least the MN is connected to a core network (CN) .

The MN and SN may be associated with one or more serving cells. In a carrier aggregation (CA) scenario, each of the MN and SN may be associated with a group of serving cells, including a primary cell (PCell) and optionally one or more secondary cells (SCells) . The group of serving cells associated with the MN is referred to as a master cell group (MCG) and the group of serving cells associated with the SN is referred to as a secondary cell group (SCG) . In some scenarios, the SCG is deactivated to reduce power consumption for example. As such, all signaling radio bearers (SRBs) and data radio bearers (DRBs) are suspended.

SUMMARY

In general, example embodiments of the present disclosure provide a solution for signaling transmission to a SN for deactivated SCG.

In a first aspect, there is provided a method of communication. The method comprises: in response to a failure of a link between a terminal device and a first network device, enabling, at the terminal device, transmission on at least one cell of a deactivated cell group of a second network device serving the terminal device; and transmitting information concerning the failure to the second network device on the at least one cell.

In a second aspect, there is provided a method of communication. The method comprises receiving, at a second network device and from a terminal device, information concerning a failure to the second network device on the at least one cell, the terminal device being served by a first network device and the second network device; and transmitting the information to the first network device.

In a third aspect, there is provided a method of communication. The method comprises enabling, at a terminal device served by first and second network devices, transmission on at least one cell of a deactivated cell group of the second network device; and transmitting a measurement report to the second network device on the at least one cell, the measurement repot being related to a quality of a channel between the terminal device and the second network device.

In a fourth aspect, there is provided a terminal device. The terminal device includes a processor; and a memory coupled to the processor and storing instructions thereon, the instructions, when executed by the processor, causing the terminal device to perform the method according to the first aspect.

In a fifth aspect, there is provided a network device. The network device includes a processor; and a memory coupled to the processor and storing instructions thereon, the instructions, when executed by the processor, causing the network device to perform the method according to the second aspect.

In a sixth aspect, there is provided a terminal device. The terminal device includes a processor; and a memory coupled to the processor and storing instructions thereon, the instructions, when executed by the processor, causing the terminal device to perform the method according to the third aspect.

In a seventh aspect, there is provided a computer-readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the first aspect.

In an eighth aspect, there is provided a computer-readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the second aspect.

In a ninth aspect, there is provided a computer-readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the third aspect.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some example embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

Fig. 1 is a block diagram of a communication environment in which embodiments of the present disclosure can be implemented;

Fig. 2 is a signaling chart illustrating the process of transmission to a deactivated network device with SCG activation in accordance with some embodiments of the present disclosure;

Fig. 3 is a signaling chart illustrating the process of transmission to a deactivated network device with random access in accordance with some embodiments of the present disclosure;

Fig. 4 is a signaling chart illustrating the process of transmission to a deactivated network device with SCG activation in accordance with some embodiments of the present disclosure;

Fig. 5 is a signaling chart illustrating the process of transmission to a deactivated network device in accordance with some embodiments of the present disclosure;

Fig. 6 is a signaling chart illustrating the process of transmission to a deactivated network device with random access in accordance with some embodiments of the present disclosure;

Fig. 7 illustrates a flow chart of an example method of communication implemented at a terminal device in accordance with some embodiments of the present disclosure;

Fig. 8 illustrates a flow chart of an example method of communication implemented at a network device in accordance with some embodiments of the present disclosure;

Fig. 9 illustrates a flow chart of an example method of communication implemented at a terminal device in accordance with some embodiments of the present disclosure; and

Fig. 10 is a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitations as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein, the term “network device” refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an Evolved NodeB (eNodeB or eNB) , a NodeB in new radio access (gNB) , a remote radio unit (RRU) , a radio head (RH) , a remote radio head (RRH) , a low power node such as a femto node, a pico node, a satellite network device, an aircraft network device, and the like. For the purpose of discussion, in the following, some example embodiments will be described with reference to eNB as examples of the network device.

As used herein, the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipments (UEs) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, tablets, wearable devices, internet of things (IoT) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices or evolved MTC (eMTC) devices, devices on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, or image capture devices such as digital cameras, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing, and the like. In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

In one example, the terminal device may be connected with the first and second network devices. One of the first and second network devices may be a master node and the other one may be a secondary node. The first and second network devices may use different radio access technologies (RATs) . In another example, the first network device may be a first RAT device and the second network device may be a second RAT device. In one embodiment, the first RAT device is eNB and the second RAT device is gNB. Information related with different RATs may be transmitted to the terminal device from at least one of the first network device and the second network device. In one embodiment, first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device. In one embodiment, information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.

Communications discussed herein may use conform to any suitable standards including, but not limited to, New Radio Access (NR) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , cdma2000, and Global System for Mobile Communications (GSM) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies.

As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “includes” and its variants are to be read as open terms that mean “includes, but is not limited to. ” The term “based on” is to be read as “based at least in part on. ” The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” The terms “first, ” “second, ” and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as “best, ” “lowest, ” “highest, ” “minimum, ” “maximum, ” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

Nowadays, people pay more and more attention to power consumption of a terminal device (e.g., a UE) and/or a network device (e.g., an eNB or a gNB) . Existing power saving solutions for CA scenario includes SCell activation and deactivation. To enable reasonable power consumption (for example, battery consumption) of UE when CA is configured, an activation/deactivation mechanism of SCells is supported. When an SCell is deactivated, the UE does not need to receive the corresponding PDCCH or PDSCH, cannot transmit in the corresponding uplink, nor is it required to perform channel quality indicator (CQI) measurements. Conversely, when an SCell is activated, the UE shall receive PDSCH and PDCCH (if the UE is configured to monitor PDCCH from this SCell) and is expected to be able to perform CQI measurements.

In addition, power saving solutions for CA scenario include Scell Dormancy. To enable fast SCell activation when CA is configured, one dormant bandwidth part (BWP) may be configured for an SCell. If the active BWP of the activated SCell is a dormant BWP, the UE stops monitoring PDCCH on the SCell but continues performing channel state information (CSI) measurements, automatic gain control (AGC) and beam management, if configured. Downlink control information (DCI) is used to control entering/leaving the dormant BWP for one or more SCell (s) or one or more SCell group (s) . The dormant BWP is one of the UE’s dedicated BWPs configured by network via dedicated RRC signaling. The SpCell and PUCCH SCell cannot be configured with a dormant BWP.

Furthermore, a power-saving solution is also needed for DC scenario. For example, SCG activation is needed in some cases. Take the EN-DC as an example. Due to maintaining two radio links simultaneously, power consumption of UE and network is a big issue. For example, in some cases, power consumption of the UE in NR network may be three to four times higher than that of the UE in the LTE network. In EN-DC deployment, the MN provides the basic coverage. When data rate requirement of the UE changes dynamically, for example, from high to low, the SN is worth considering to be deactivated or suspended to reduce power consumption. Therefore, an efficient SCG deactivation mechanism should be specified. This efficient SCG deactivation mechanism may also be applied to other MR-DC deployments, including but not limited to NGEN-DC, NR-DC. The terms “SCG suspension” and “SCG deactivation” are used interchangeably herein. The resumption of the suspended SCG may be referred to as “SCG resumption” or “SCG activation” , which expresses the same meaning.

Three options regarding modeling of the SCG suspension have been proposed. In Option 1, all serving cells associated with the SN including PScell and SCells are activated and the active BWP is configured as a dormant BWP. In Option 2, all serving cells associated with the SN including PScell and SCells are deactivated. In Option 3, the SCells of the SCG should be deactivated, while the PScell of the SCG should be activated and the active BWP is configured as a dormant BWP. The possible mechanisms for activating or deactivating SCG are via RRC signaling, MAC CE, DCI, inactivity timer or similar behavior and reuse signaling of ‘dormancy’ behavior (if specified) . Moreover, there are also some other potential aspects concerning SGC activation/deactivation being considered, which are radio link monitoring (RLM) for the deactivated SCG and measurement of deactivated SCG.

For example, in one example, with the above RRC signaling mechanism, in case of new UL data arriving or new signaling arriving towards a SN, the UE may initiate SCG activation request procedure to a MN or the SN. Specifically, an SCG activation request to MN may be performed by sending a RRC message to the MN. Alternatively, the SCG activation request to SN may be performed by initiating a random access to the SN with or without RRC signaling.

As can be seen from the above, different from SCell activation/deactivation and SCell dormancy (where PSCell can maintain data transmission, thus no high layer handling) , in the SCG suspension, the SCG transmission for all SRBs and DRBs shall be suspended. However, the inventors noticed that there are some cases (the details thereof will be discussed below) in which the transmission of signaling from the UE towards SN is triggered, for example, the message for fast MCG link recovery purpose or a SN Measurement report. Whereas, so far, there is no solution on how to transmit the signaling, if needed, to the SN in the scenario in which SCG is deactivated. In other words, an efficient and robust solution on how to transmit the signaling to a SN when the SN is deactivated has not been specified. The efficient and robust mechanism can be applied to a variety of MR-DC deployments, including but not limited to the EN-DC, NGEN-DC, NR-DC deployments.

For example, in some cases, it is possible that a radio link between a UE and SN fails, for example, the UE detect a radio link failure on the MCG. The UE may determine the MCG radio link as failed in many situation, including, but not limited to, upon random access problem indication from MCG MAC, upon indication of consistent uplink LBT failures from MCG MAC, upon indication from MCG RLC that the maximum number of retransmissions has been reached.

Upon the failure of the link on MCG, the UE may perform RRC connection re-establishment procedure. For the RRC connection re-establishment, the UE shall perform cell selection to select one cell that satisfies a certain criteria. However since the criteria used for selecting one cell in this RRC connection re-establishment procedure is not very strict, that is, the cell being selected may not be an optimal one. As a result, it is likely that the quality of the cell being re-selected is not satisfying, resulting in low rate of success for the RRC re-establishment. Accordingly, fast MCG link recovery is introduced, in which MCG Failure Information message is transmitted to the MN via the SCG. As the radio link monitoring, measurement, and maybe beam management are still supported at least for PSCell, the radio condition of SCG is under good condition. As a result, there is a high possibility of success of performing MCG link recovery via the deactivated SCG. Therefore, RRC connection re-establishment procedure may be avoided and the rate of success of MCG link recovery via the suspended SCG is higher than RRC re-establishment.

Whereas, when SCG is deactivated, a solution on how the UE performs MCG link recovery to SCG is still not specified. Considering that the radio link of MCG served by the MN is critical to the UE and losing radio connection to the MN which is the MN will bring a problem to the UE, a solution on fast MCG link recovery via the suspended SCG deactivated needs to be provided.

Therefore, according to example embodiments of the present disclosure, there is provided a solution. In this solution, in response to a failure of a link between a UE and MN, the UE enables transmission on at least one cell of a deactivated cell group of SN serving the UE. Then, the UE transmits information concerning the failure to the SN on the at least one cell. As a result, a solution on fast MCG link recovery in case of the SCG deactivated is provided, thereby improving the rate of success of MCG link recovery.

Fig. 1 shows an example communication environment 100 in which example embodiments of the present disclosure can be implemented. In the example of Fig. 1, a plurality of

network devices

110, 120 are deployed to serve a terminal device 130. The network device 110 serves the terminal device 130 as the MN, while the network device 120 serves the terminal device 130 as the SN.

The serving areas of the

network devices

110, 120 are called cells. As shown in Fig. 1, a group of cells of the network device 110 includes a primary cell 150-1 and a secondary cell 150-2. Since the network device 110 serves as the MN, the group of cells of the network device 110 is referred to as MCG 150 and the primary cell 150-1 is referred to as PCell 150-1.

A group of cells of the network device 120 includes a primary cell 160-1 and a secondary cell 160-2. Since the network device 120 serves as the SN, the group of cells of the network device 120 is referred to as SCG 160 and the primary cell 160-1 is referred to as PSCell 160-1. The PCell 150-1 and PSCell 160-1 may be collectively referred to as SpCell.

It is to be understood that the number of SCells in Fig. 1 is given for the purpose of illustration, without suggesting any limitations to the present disclosure. The

network devices

110, 120 may provide any suitable number of SCells for serving the terminal device 130.

Communications between the terminal device 130 and the

network devices

110, 120 may be implemented according to any proper communication protocol (s) . Communication in a direction from the terminal device 130 towards the

network device

110 or 120 is referred to as UL communication, while communication in a reverse direction from the

network device

110 or 120 towards the terminal device 130 is referred to as DL communication. The terminal device 130 may move amongst the coverage areas of the

network devices

110, 120 and possibly other network devices.

In UL communication, the terminal device 130 may transmit UL data and radio resource control (RRC) signaling to the

network device

110 or 120 via a UL channel. In some examples, the UL data may be transmitted in a physical uplink shared channel (PUSCH) and/or any other UL channels that are available used for data transmission. In some examples, the RRC signaling may be transmitted in a physical uplink shared channel (PUSCH) . In DL transmission, the

network device

110 or 120 may transmit DL data and RRC signaling to the terminal device 130 via a DL channel. In some examples, the DL data may be transmitted in a physical downlink shared channel (PDSCH) and/or any other DL channels that are available used for data transmission. In some examples, the RRC signaling may be transmitted in a physical downlink shared channel (PDSCH) .

A DC provided by the

network devices

110, 120 may include any suitable type of multi-radio dual connectivity (MR-DC) , including but not limited to E-UTRA (Evolved Universal Terrestrial Radio Access) -NR dual connectivity (EN-DC) , next generation E-UTRA-NR dual connectivity (NGEN-DC) and NR-DC. In the case of EN-DC, the network device 110 is an eNB and the network device 120 is a gNB, for example, enhanced-gNB (en-gNB) . In the case of NGEN-DC, the network device 110 is a ng-eNB and the network device 120 is a gNB. In the case of NR-DC, the

network devices

110 and 120 are both gNBs.

At least the network device 110 is connected to a CN 140. The CN 140 may include functional elements and/or network functions (which may be collectively referred to as network elements, NEs) to support a variety of functions. Specifically, the network device 110 may be connected a NE 142, which may depend on network types. In the case of EN-DC, the NE 142 may include a mobility management entity (MME) . The network device 110 may communicate with the MME via S1 interface and the

network devices

110 and 120 may communicate with each other via X2 interface for a control plane. In the cases of NGEN-DC and NR-DC, the NE 142 may include an access and mobility management function (AMF) . The network device 110 may communicate with the AMF via NG interface and the

network devices

110 and 120 may communicate with each other via Xn interface for the control plane. Although not shown, the CN 140 may include one or more other functional elements and/or network functions such as a session management function (SMF) , a policy control function (PCF) , a network exposure function (NEF) , and/or the like. The scope of the embodiments of the present disclosure is not limited in this regard.

It is to be understood that the number and type of devices in Fig. 1 are given only for the purpose of illustration, without suggesting any limitations to the present disclosure. The communication environment 100 may include any suitable number of network devices and/or terminal devices adapted for implementing implementations of the present disclosure. Further, the communication environment 100 may include any other devices than the network devices and the terminal devices, such as a core network element, but they are omitted herein so as to avoid obscuring the present disclosure.

Figs. 2-3 show signaling charts illustrating the process of transmission to a deactivated network device 120 when a radio link between the terminal device 130 and the network device 120 fails.

Fig. 2 is a signaling chart illustrating process 200 of transmission to the deactivated network device 120 with SCG activation in accordance with some embodiments of the present disclosure.

For the purpose of discussion, the process 200 will be described with reference to Fig. 1. The process 200 may involve the terminal device 130, the network device 110 and the network device 120.

As shown in Fig. 2, in some embodiments, the terminal device 130 may detect 202 a failure of a link between a terminal device 130 and a first network device 110. In other words, there is a radio link failure on the MGC 50.

In some embodiments, upon the failure of the link, and if the fast MCG link recovery is configured, the terminal device 130 may trigger a fast MCG link recovery. For example, during the fast MCG link recovery, the terminal device 130 may suspend transmissions on the MCG 150 for all radio bearers. Then, the terminal device 130 may activate 204 the SCG 160 of the network device 120, such that the transmission on the SCG 160 of the network device 120 serving the terminal device 130 is enabled.

In some embodiments, the terminal device 130 may activate the SCG 160 of the network device 120 by transmitting a SCG activation request to the network device 120. In such embodiments, the SCG activation request may include an activation cause. The activation cause may be provided to the network device 120 as MCG link recovery or mo-signaling, for example.

In some embodiments, upon transmission on the SCG 160 of the second network device 120 is activated, the terminal device 130 transmits 206 information concerning the failure on the activated SCG 160. The information concerning the failure on the activated SCG 160 may be based on any suitable information. For example, the information concerning the failure is a MCG Failure Information message. The MCG Failure Information message may be submitted to lower layers of the terminal device for transmission via split SRB1 or SRB3.

For examples, the terminal device 130 may include the MCG Failure Information message the measurement results available according to current measurement configuration of both the network device 110 and the network device 120. Once the fast MCG link recovery is triggered, the terminal device 130 may maintain the current measurement configurations from both the network device 110 and the network device 120, and continues measurements based on the configuration from the network device 110 and the network device 120, if possible. The terminal device 130 may initiate the RRC connection re-establishment procedure if it does not receive an RRC reconfiguration message or RRC release message within a certain time after fast MCG link recovery was initiated.

In some embodiments, upon receipt of the information concerning the failure, the network device 120 transmits 208 the information to the network device 110. Upon receipt of the information, the network device 110 may transmit 210 RRC reconfiguration message or RRC release message to the network device 120. The network device 120 then transmit 212 the message to the terminal device 130. In case of SRB3, the network device 110 may transmit 210 the RRC message to the network device 120. Then, the network device 120 forwards it to the terminal device 130 via SRB3. In this case, the RRC message from the network device 110 may be embedded in DLInformationTransferMRDC.

In some embodiments, upon receipt of the RRC reconfiguration message, the terminal device 130 may transmit 214 the network device 110 with a RRC reconfiguration Complete message. Upon receipt of the RRC release message, the terminal device 130 may release all the radio bearers and configurations.

With the above solution, when the a MCG 150 link failure occurs and the SCG 160 is deactivated, the terminal device 130 is able to transmit, to the network device 110, information concerning the failure to the network device 120 on the at least one cell via the SCG 160 by activating the SCG 160 first.

In some embodiments, upon transmitting the information concerning the link failure to the network device 120, the terminal device 130 may start a timer T1, monitoring the fast MCG link recovery process. Table 1 below shows the attributes of the timer. As shown, the terminal device 130 may stop the timer upon the resumption of MCG transmission, upon reception of RRC Release, or upon initiating the re-establishment procedure. At the expiry of the timer, the terminal device 130 may perform actions such as RRC Connection re-establishment as mentioned above. In some embodiments, for example, T1 may be an existing timer currently used. Alternatively, T1 may also be a new timer which has not been used before.

Table 1 Attributes of T1

Alternatively, in some embodiments, if MCG link failure is detected and SCG is deactivated, the terminal device 130 may start the timer T1 upon initiation of SCG activation request procedure, that is, upon transmission of the request to activate SCG 160 of the network device 120. As such, the timer T1 could start upon the SCG activation request, in other words, the time consumed by the SCG activation process (if there is one) will also be taken into account. As a result, in case the time consumed by the SCG activation process is too long, the timer would expire, such that the fast MCG link recover process may be terminated and the terminal device 130 may decide to initiate other process, for example, RRC connection re-establishment procedure as shown.

In the above embodiments, the terminal device is able to transmit, to the network device 120, information concerning the radio link failure between the terminal device 130 and a network device 120.

In some embodiments, upon a radio link failure on the MCG 150, the terminal device 130 may enable 302 transmission on a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell. Accordingly, the terminal device 130 may transmit the information to the network device 120, for example, during a random access procedure on the primary cell 160-1. Fig. 3 illustrates a signaling chart illustrating the process of transmission to the deactivated network device 120 with random access in accordance with some embodiments of the present disclosure. For the purpose of discussion, the process 300 will be described with reference to Fig. 1. The process 300 may involve the terminal device 130, the network device 110 and the network device 120.

In some embodiments, the terminal device 130 may detect a radio link failure on the MCG 150. However, since the network device 120 is deactivated, in some embodiments, the terminal device 130 may enable transmission on a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell. For example, the terminal device 130 may at least switch dormant BWP to non-dormant BWP of PScell 160-1. In another example, the terminal device 130 may activate PScell 160-1so as to wake the PScell 160-1. Alternatively, the terminal device 130 may awake all the serving cell associated with the network device 120.

Alternatively or in addition, the terminal device 130 may resume the SCG transmission of signaling radio bearer 1 (SRB1) if it is configured as split SRB. As a further alternative, the terminal device 130 may resume the signaling radio bearer 3 (SRB3) . Accordingly, the terminal device 130 may submit the information, for example, MCG failure Information message to lower layer (MAC) for transmission using split SRB1 or SRB3. That is, the RRC layer of the terminal device 130 submits to the MAC layer the message such that a random access procedure is triggered automatically on the PSCell 160-1.

The random access procedure on the PSCell 160-1 may be based on any suitable type of random access. In some embodiments, the random access procedure on the PSCell 160-1 may be a four-step procedure. In such embodiments, the terminal device 130 may transmit 304, to the network device 120, a random access request which may include a random access preamble in MSG1. Upon receipt of the MSG1, the network device 120 may transmit 306 a response with random access response (RAR) . After that, the terminal device 130 may transmit 308, to the network device 120, MCG failure Information using the SCG leg of split SRB1 or SRB3 in MSG3.

Alternatively or in addition, in some embodiments, the random access procedure on the PSCell 160-1 may be a two-step procedure (not shown) . In such embodiments, the terminal device 130 may transmit, to the network device 120, MCG failure Information in MSG A using the SCG leg of split SRB1 or SRB3.

In addition, upon receipt of the MCG failure Information, the network device 120 may transmit 310 it to the network device 110. For example, the network device 120 may directly forward the MCG failure Information to the network device 110. The network device 110 may transmit 312 a response with RRC reconfiguration message or RRC release message to the network device 120 in MSG4 in case of the four-step procedure or MSGB in case of the two-step procedure. As a result, the network device 120 can transmit 314 the response back to the terminal device 130. SCG leg of split SRB1 or SRB3 may be used for the RRC reconfiguration message or RRC release message, depending on which one (SRB1 or SRB3) is used when the information is transmitted from the terminal device 130. As a response, the terminal device 130 may transmit RRC reconfiguration complete message.

Alternatively or in addition, upon determining that the random access procedure is complete or upon receiving RRC reconfiguration message from the network device 110, the terminal device 130 may enable transmission on all serving cells of the cell group, and resume all the other radio bearers. In such embodiments, for example, the network device 110 may resume all the other radio bearers and awake all serving cells to activate the SCG 160. As such, the SCG 160 may be used for further transmission, if any.

Alternatively or in addition, in some embodiments, upon determining that the random access procedure is complete or upon receiving RRC reconfiguration message from the network device 110, the terminal device 130 may disable the transmission on the primary cell 160-1 of the SCG 160 and suspend the split SRB1 or the SRB3 between the terminal device 130 and the network device 120. In addition, for example, the terminal device 130 may also reset MAC and at least switch to dormant BWP of PScell or deactivated PScell or sleep all serving cells. As a result, power saving can further be achieved for DC/CA scenario.

In some embodiments, the network device 110 may indicate the activation of SCG 160 in RRC reconfiguration. If SCG activation indication message is included in the RRC reconfiguration message from network device 110, the terminal device may activate the SCG. Whereas, if SCG activation indication message is not included in the RRC reconfiguration message from the network device 110 or SCG deactivation indication is included in the RRC reconfiguration from the network device 110, the terminal device 130 may suspend SCG transmission of split SRB1 and SRB3, reset SCG MAC, switch to dormant BWP or deactivate PScell 160-1, so as to set SCG 160 back to deactivated.

In the above embodiments, the terminal device 130 may transmit the information to the network device 120 during a random access procedure on the primary cell 160-1, no SCG activation is required at least before the information (such as the MCG failure information message) is forwarded via the network device 120 to the network device 110. After receiving the information, the network device 110 may indicate the activation of SCG 60 in RRC reconfiguration. That is, the network device 110 can decide afterward whether to activate the SCG 60.

In the following, some other cases concerning measurement report for SRB3 will be described.

Measurements may be configured independently by the MN and by the SN. If the SN is a gNB (i.e., for EN-DC, NGEN-DC and NR-DC) , a UE may be configured to establish a SRB (i.e., SRB3) with the SN to enable RRC protocol data units (PDUs) for the SN to be transmitted directly between the UE and the SN. RRC PDUs for the SN can only be transmitted directly to the UE for SN RRC reconfiguration, without requiring any coordination with the MN. When SRB3 is not configured, reports for measurements configured by the SN may be sent on SRB1. When SRB3 is configured, reports for measurements configured by the SN are sent on SRB3. Measurement reporting for mobility within the network device can be done directly from the UE to the SN if SRB3 is configured. The measurement reporting/RRC reconfiguration transmitted by SRB3 can enable fast mobility scenario, which is very useful for NR, usually being deployed with small cells.

Upon the SCG is deactivated, the terminal device may suspend the measurement configured by the SN. Then upon the SCG is activated, the terminal device may resume the measurement configured by the SN.

However, upon SCG deactivation, if measurement configured by the SN is not suspended at the UE, an efficient and robust mechanism on how to transmit the SN measurement report for SRB3 to the deactivated SN should be specified.

Therefore, according to example embodiments of the present disclosure, there is provided a solution for transmitting a measurement report to the SN in case of SCG deactivated. In this solution, the UE served by the MN and SN enables transmission on at least one cell of the deactivated SCG of the SN. Then, the UE transmits a measurement report to the SN on the at least one cell. The measurement report is related to a quality of a channel between the UE and the SN. As such, the UE is able to transmit the SN measurement report directly to the SN, thereby enabling fast mobility scenario, which is very useful for NR as mentioned above.

Figs. 4-6 show signaling charts illustrating the process of transmission to a deactivated network device 120 SN measurement report.

Fig. 4 is a signaling chart illustrating process 400 of transmission to the deactivated network device 120 with SCG activation in accordance with some embodiments of the present disclosure.

For the purpose of discussion, the process 400 will be described with reference to Fig. 1. The process 400 may involve the terminal device 130, the network device 110 and the network device 120.

As a precondition, the SCG 160 of the network device 120 is suspended or deactivated. In some embodiments, for example, the terminal device may determine 402 that a measurement report for SN configured measurement report is triggered and SRB3 is configured. Accordingly, the terminal device 130 may enable 404 transmission on at least one cell of a deactivated cell group of the network device 120 by activating the SCG 160 of the network device 120 first.

In some embodiments, the terminal device 130 may activating the SCG 160 of the network device 120 by transmitting a SCG activation request to the network device 120. In such embodiments, the SCG activation request may include an activation cause. The activation cause may be provided to the network device 120 as mo-signaling, measurement report, for example. Alternatively, the terminal device 130 also may activate the SCG 160 of the network device 120 by transmitting a SCG activation request to the network device 110. The activation cause may be provided to the network device 110 as mo-signaling, measurement report, for example.

In some embodiments, upon transmission on the SCG 160 of the second network device 120 is activated, the terminal device 130 transmits 406 the measurement report on the activated SCG 160 using SRB3.

Alternatively or in addition, in some embodiment, the network device 120 may transmit RRC reconfiguration for intra-SN mobility in the contention resolution message (not shown) . In such embodiments, intra-SN mobility may be the PScell change or Scell change/addition/release.

With the above solution, the terminal device is able to transmit the measurement report directly to the network device 120 if SRB3 is configured. Accordingly, mobility within the network device 120 can be done directly from the terminal device 130 to the network device 120 if SRB3 is configured. NR is usually deployed with small cells. Therefore, the measurement report/RRC reconfiguration transmitted by SRB3 can enable fast mobility scenario, which is useful for NR.

Alternatively or in addition, in some embodiment, if the SCG 160 is not activated successfully, the terminal device 130 may transmit the SN measurement report to the network device 120 via the network device 110. Fig. 5 is a signaling chart illustrating the process 500 of transmission to a deactivated network device in accordance with some embodiments of the present disclosure. As shown in Fig. 5, for example, the terminal device 130 may determine 502 that the SCG 160 is not activated successfully. Then, the terminal device 130 may transmit 504 the measurement report to the network device 110. After that, the network device 110 may transmit 506 the measurement report to the network device 120. In such embodiments, the measurement report, such as the MeasurementReport message is sent via network device 110 embedded in RRC message ULInformationTransferMRDC.

In some embodiments, when the SCG 160 is deactivated, the terminal device 130 may enable transmission on a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell. Accordingly, the terminal device 130 may transmit the SN measurement report to the network device 120, for example, during a random access procedure on the primary cell 160-1. Fig. 6 is a signaling chart illustrating the process 600 of transmission to a deactivated network device with random access in accordance with some embodiments of the present disclosure.

For the purpose of discussion, the process 600 will be described with reference to Fig. 1. The process 600 may involve the terminal device 130, the network device 110 and the network device 120.

In some embodiments, the terminal device 130 may determine that a measurement report for SN configured measurement is triggered, if SRB3 is configured and SCG is suspend, in some embodiments, the terminal device 130 may enable 602 transmission on a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell. For example, the terminal device 130 may at least switch dormant BWP to non-dormant BWP of PScell 160-1. In another example, the terminal device 130 may activate PScell 160-1so as to wake the PScell 160-1. Alternatively, the terminal device 130 may awake all the serving cells associated with the network device 120.

Alternatively or in addition, the terminal device 130 may resume the signaling radio bearer 3 (SRB3) . Accordingly, the terminal device 130 may submit the SN measurement report to lower layer (MAC) for transmission using SRB3. That is, the RRC layer of the terminal device 130 submits to the MAC layer the message such that a random access procedure is triggered automatically on the PSCell 160-1.

The random access procedure on the PSCell 160-1 may be based on any suitable type of random access. In some embodiments, the random access procedure on the PSCell 160-1 may be a four-step procedure. In such embodiments, the terminal device 130 may transmit 604, to the network device 120, a random access request which may include a random access preamble in MSG1. Upon receipt of the MSG1, the network device 120 may transmit 606 a response with random access response (RAR) . After that, the terminal device 130 may transmit 608, to the network device 120, SN measurement report using the SRB3 in MSG3.

Alternatively or in addition, in some embodiments, the random access procedure on the PSCell 160-1 may be a two-step procedure (not shown) . In such embodiments, the terminal device 130 may transmit, to the network device 120, SN measurement report in MSG A using SRB3.

Alternatively or in addition, in some embodiments, upon receipt of the SN measurement report, the network device 120 may transmit 610 RRC reconfiguration message for intra-SN mobility in the contention resolution message in MSG 4. In such embodiments, the RRC reconfiguration message may include information on PScell change or Scell change/addition/release, for example. As a response, the terminal device 130 may transmit RRC reconfiguration complete message.

Alternatively or in addition, in some embodiments, upon determining that the random access procedure is complete (e.g., after receiving MSG4) , the terminal device 130 may enable transmission on one or more secondary cells of the cell group and resume all the SCG transmission of all the other radio bearers. In such embodiments, for example, the network device 110 may resume all the other radio bearers and awake all serving cells to activate the SCG 160. As such, the SCG 160 may be used for further transmission, if any.

Alternatively or in addition, in some other embodiments, upon determining that the random access procedure is complete, the terminal device 130 may disable the transmission on the primary cell 160-1 of the SCG 160 and suspend the SRB3 between the terminal device 130 and the network device 120. In addition, for example, the terminal device 130 may also reset MAC and at least switch to dormant BWP of PScell or deactivated PScell or sleep all serving cells. As a result, power saving can further be achieved for DC/CA scenario.

Alternatively or in addition, in some embodiments, if the random access procedure mentioned above is not performed successfully, the terminal device 130 may transmit the SN measurement report to the network device 120 via the network device 110. Specifically, the terminal device 130 may transmit the measurement report to the network device 110. After that, the network device 110 may transmit the measurement report to the network device 120. In such embodiments, the measurement report, such as the MeasurementReport message is sent via network device 110 embedded in RRC message ULInformationTransferMRDC.

In some embodiments, the network device 120 may indicate the activation of SCG 160 in RRC reconfiguration. If SCG activation indication message is included in the RRC reconfiguration message from network device 120, the terminal device may activate the SCG, and resume SCG transmission of all the other radio bearers. Whereas, if SCG activation indication message is not included in the RRC reconfiguration message from the network device 120 or SCG deactivation indication is included in the RRC reconfiguration message from the network device, the terminal device 130 may suspend SCG transmission of SRB3, reset SCG MAC, switch to dormant BWP or deactivate PScell 160-1, so as to set SCG 160 back to deactivated.

In the above embodiments, the terminal device 130 may transmit the measurement report to the network device 120 during a random access procedure on the primary cell 160-1, no SCG activation is required before the information (such as the MCG failure information message) is forwarded via the network device 120 to the network device 110. After receiving the information, the network device 120 may indicate the activation of SCG 60 in RRC reconfiguration. That is, the network device 120 can decide afterward whether to activate the SCG 60 or set it back to deactivated.

Fig. 7 illustrates a flowchart of an example method 700 in accordance with some embodiments of the present disclosure. The method 700 can be implemented at a terminal device 130 as shown in Fig. 1. It is to be understood that the method 700 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard. For the purpose of discussion, the method 700 will be described from the perspective of the terminal device 130 with reference to Fig. 1.

At block 710, in response to a failure of a link between a terminal device 130 and the first network device 110, the terminal device 130 enables transmission on at least one cell of a deactivated cell group of the second network device 120 serving the terminal device 130. Then, at block 720, the terminal device 130 transmits information concerning the failure to the second network device 120 on the at least one cell.

In some embodiments, the terminal device 130 enables transmission on at least one cell of the cell group comprises that the terminal device 130 activates the cell group of the second network device 120.

In some embodiments, the terminal device 130 activates the cell group of the second network device 120 comprises that the terminal device 130 transmits a request to active the cell group to the second network device 120; and starting a timer upon transmission of the request.

In some embodiments, the terminal device 130 activates the cell group comprise that the terminal device 130 transmits a request to active the cell group to the second network device 120. The request comprises a cause indicating at least one of: a signaling to be transmitted from the terminal device, or the failure of the link.

In some embodiments, the terminal device 130 enables transmission on at least one cell of the cell group comprises that the terminal device 130 enabling transmission on a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell.

In some embodiments, a split signaling radio bearer 1 (SRB1) or a signaling radio bearer 3 (SRB3) between the terminal device 130 and the second network device 120 is resumed.

In some embodiments, the terminal device 130 transmits the information concerning the failure comprises that the terminal device 130 transmits the information during a random access procedure on the primary cell.

In some embodiments, the method 700 further comprises: in accordance with a determination that the random access procedure is complete, the terminal device 130 enables transmission on one or more secondary cells of the cell group.

In some embodiments, the method 700 further comprises: in accordance with a determination that the random access procedure is complete, the terminal device 130 disables the transmission on the primary cell of the cell group and suspending the split SRB1 or the SRB3 between the terminal device 130 and the second network device 120.

In some embodiments, the method 700 comprises that the terminal device 130 receives a message from the second network device 120. The message is forwarded by the second network device 120 from the first network device110. In accordance with a determination that the message indicates activation of the cell group, the terminal device 130 enables transmission on one or more secondary cells of the cell group. In accordance with a determination that the message indicates deactivation of the cell group, the terminal device 130, disables the transmission on the primary cell of the cell group and suspending the split SRB1 or the SRB3 between the terminal device 130 and the second network device 120.

Fig. 8 illustrates a flowchart of an example method 800 in accordance with some embodiments of the present disclosure. The method 800 can be implemented at the second network device 120 as shown in Fig. 1. It is to be understood that the method 800 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard. For the purpose of discussion, the method 800 will be described from the perspective of the second network device 120 with reference to Fig. 1.

At block 810, the second network device 120 receives from a terminal device 130 information concerning a failure to the second network device 120 on the at least one cell. The terminal device 130 is served by a first network device 110 and the second network device 120. Then, at block 820, the second network device 120 transmits the information to the first network device 110.

In some embodiments, the second network device 120 receives the information concerning the failure comprises that the second network device 120 receives the information during a random access procedure performed by the terminal device 130 on a primary cell of the cell group.

Fig. 9 illustrates a flowchart of an example method 900 in accordance with some embodiments of the present disclosure. The method 900 can be implemented at the terminal device 130 as shown in Fig. 1. It is to be understood that the method 900 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard. For the purpose of discussion, the method 900 will be described from the perspective of the terminal device 130 with reference to Fig. 1.

At block 910, the terminal device 130 served by first and second network devices, enables transmission on at least one cell of a deactivated cell group of the second network device 120. Then, at block 920, the terminal device 130 transmits a measurement report to the second network device 120 on the at least one cell. The measurement repot is related to a quality of a channel between the terminal device 130 and the second network device 120.

In some embodiments, the terminal device 130 activates the cell group comprises that the terminal device 130 transmits a request to active the cell group to at least one of the first and second network devices. The request comprises a cause indicating at least one of: a signaling to be transmitted from the terminal device 130, or the measurement report.

In some embodiments, the terminal device 130 enables transmission on at least one cell of the cell group comprises that the terminal device 130 enables transmission a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell.

In some embodiments, a signaling radio bearer 3 (SRB3) between the terminal device 130 and the second network device 120 is resumed.

In some embodiments, the terminal device 130 transmits the measurement report comprises that the terminal device 130 transmits the measurement report during a random access procedure on the primary cell.

In some embodiments, the method further comprises in accordance with a determination that the random access procedure is complete, the terminal device 130 enables transmission on one or more secondary cells of the cell group.

In some embodiments, the method further comprises in accordance with a determination that the random access procedure is complete, the terminal device 130 disables the transmission on the primary cell of the cell group and suspending the SRB3 between the terminal device 130 and the second network device 120.

In some embodiments, the method further comprises the terminal device 130 receives a message from the second network device 120. In accordance with a determination that the message indicates activation of the cell group, the terminal device 130 enables transmission on one or more secondary cells of the cell group. In accordance with a determination that the message indicates deactivation of the cell group, the terminal device 130 disables the transmission on the primary cell of the cell group and suspending the SRB3 between the terminal device 130 and the second network device 120.

In some embodiments, there is provided a method which can be implemented at a network device, for example, the network device 110 as shown in Fig. 1. The method may comprise acts performed by the network device 110 as described with reference to Figs. 2-6.

In some embodiments, there is provided a method which can be implemented at a network device, for example, the network device 120 as shown in Fig. 1. The method may comprise acts performed by the network device 120 as described with reference to Figs. 2-6.

Fig. 10 is a simplified block diagram of a device 1000 that is suitable for implementing embodiments of the present disclosure. The device 1000 can be considered as a further example implementation of the terminal device 130, the network device 120, or the network device 110 as shown in Fig. 1. Accordingly, the device 1000 can be implemented at or as at least a part of the terminal device 130, the network device 120, or the network device 110.

As shown, the device 1000 includes a processor 1010, a memory 1020 coupled to the processor 1010, a suitable transmitter (TX) and receiver (RX) 1040 coupled to the processor 1010, and a communication interface coupled to the TX/RX 1040. The memory 1010 stores at least a part of a program 1030. The TX/RX 1040 is for bidirectional communications. The TX/RX 1040 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2 interface for bidirectional communications between eNBs, S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB, Un interface for communication between the eNB and a relay node (RN) , or Uu interface for communication between the eNB and a terminal device.

The program 1030 is assumed to include program instructions that, when executed by the associated processor 1010, enable the device 1000 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to Figs. 2-9. The embodiments herein may be implemented by computer software executable by the processor 1010 of the device 1000, or by hardware, or by a combination of software and hardware. The processor 1010 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1010 and memory 1010 may form processing means 1050 adapted to implement various embodiments of the present disclosure.

The memory 1010 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer-readable storage medium, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 1010 is shown in the device 1000, there may be several physically distinct memory modules in the device 1000. The processor 1010 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1000 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to Figs. 2-7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A method of communication comprising:

in response to a failure of a link between a terminal device and a first network device, enabling, at the terminal device, transmission on at least one cell of a deactivated cell group of a second network device serving the terminal device; and

transmitting information concerning the failure to the second network device on the at least one cell.
The method of claim 1, wherein enabling transmission on at least one cell of the cell group comprises:

activating the cell group of the second network device.
The method of claim 2, wherein activating the cell group of the second network device comprises:

transmitting a request to active the cell group to the second network device; and

starting a timer upon transmission of the request.
The method of claim 2, wherein activating the cell group comprises:

transmitting a request to active the cell group to the second network device, the request comprising a cause indicating at least one of:

a signaling to be transmitted from the terminal device, or

the failure of the link.
The method of claim 1, wherein enabling transmission on at least one cell of the cell group comprises:

enabling transmission on a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell.
The method of claim 5, wherein a split signaling radio bearer 1 (SRB1) or a signaling radio bearer 3 (SRB3) between the terminal device and the second network device is resumed.
The method of claim 5, wherein transmitting the information concerning the failure comprises:

transmitting the information during a random access procedure on the primary cell.
The method of claim 7, further comprising:

in accordance with a determination that the random access procedure is complete, enabling transmission on one or more secondary cells of the cell group.
The method of claim 7, further comprising:

in accordance with a determination that the random access procedure is complete, disabling the transmission on the primary cell of the cell group and suspending the split SRB1 or the SRB3 between the terminal device and the second network device.
The method of claim 6, further comprising:

receiving a message from the second network device, the message being forwarded by the second network device from the first network device;

in accordance with a determination that the message indicates activation of the cell group, enabling transmission on one or more secondary cells of the cell group; and

in accordance with a determination that the message indicates deactivation of the cell group, disabling the transmission on the primary cell of the cell group and suspending the split SRB1 or the SRB3 between the terminal device and the second network device.
A method of communication comprising:

receiving, at a second network device and from a terminal device, information concerning a failure to the second network device on the at least one cell, the terminal device being served by a first network device and the second network device; and

transmitting the information to the first network device.
The method of claim 11, wherein receiving the information concerning the failure comprises:

receiving the information during a random access procedure performed by the terminal device on a primary cell of the cell group.
A method of communication comprising:

enabling, at a terminal device served by first and second network devices, transmission on at least one cell of a deactivated cell group of the second network device; and

transmitting a measurement report to the second network device on the at least one cell, the measurement repot being related to a quality of a channel between the terminal device and the second network device.
The method of claim 13, wherein enabling transmission on at least one cell of the cell group comprises:

activating the cell group of the second network device.
The method of claim 14, wherein activating the cell group comprises:

transmitting a request to active the cell group to at least one of the first and second network devices, the request comprising a cause indicating at least one of:

a signaling to be transmitted from the terminal device, or

the measurement report.
The method of claim 13, wherein enabling transmission on at least one cell of the cell group comprises:

enabling transmission a primary cell of the cell group based on a non-dormant bandwidth part (BWP) or by activating the primary cell.
The method of claim 16, wherein a signaling radio bearer 3 (SRB3) between the terminal device and the second network device is resumed.
The method of claim 16, wherein transmitting the measurement report comprises:

transmitting the measurement report during a random access procedure on the primary cell.
The method of claim 18, further comprising:

in accordance with a determination that the random access procedure is complete, enabling transmission on one or more secondary cells of the cell group.
The method of claim 18, further comprising:

in accordance with a determination that the random access procedure is complete, disabling the transmission on the primary cell of the cell group and suspending the SRB3 between the terminal device and the second network device.
The method of claim 17, further comprising:

receiving a message from the second network device;

in accordance with a determination that the message indicates activation of the cell group, enabling transmission on one or more secondary cells of the cell group; and

in accordance with a determination that the message indicates deactivation of the cell group, disabling the transmission on the primary cell of the cell group and suspending the SRB3 between the terminal device and the second network device.
A terminal device comprising:

a processor; and

a memory coupled to the processor and storing instructions thereon, the instructions, when executed by the processor, causing the terminal device to perform the method according to any of claims 1 to 10.
A network device comprising:

a processor; and

a memory coupled to the processor and storing instructions thereon, the instructions, when executed by the processor, causing the network device to perform the method according to any of claims 11 to 12.
A terminal device comprising:

a processor; and

a memory coupled to the processor and storing instructions thereon, the instructions, when executed by the processor, causing the terminal device to perform the method according to any of claims 13 to 21.
A computer-readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method according to any of claims 1 to 10.
A computer-readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method according to any of claims 11 to 12.
A computer-readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method according to any of claims 13 to 21.