Cell switch procedure

Abstract

Example embodiments of the present disclosure are directed to a cell switch procedure. In a method, a first apparatus receives, from a second apparatus, a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus. The first apparatus performs a random access channel (RACH)-less access to a third apparatus of the at least one candidate apparatus. The first apparatus transmits data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

Description

CELL SWITCH PROCEDUREFIELD

[0001] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for cell switch procedure.BACKGROUND

[0002] A communication network may serve as a facility that enables communications between two or more communication devices or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network. The communication network may operate in accordance with standards such as those provided by Third Generation Partnership Project (3 GPP) or European Telecommunications Standards Institute (ETSI). Examples of standards provided by 3GPP are the so-called 3GPP standards for cellular technology generations, such as 3GPP standards for 4G technology, 5G technology, 6G technology etc.

[0003] With the continuous development of mobile networks, managing and optimizing user mobility between different network nodes has become crucial. Modern mobile communication systems require seamless connectivity between various network nodes to ensure efficient and reliable handovers. In order to ensure the communication continuousness in the wireless communication system, multiple technologies are proposed, such as cell switch. During the cell switch, the terminal device may switch among different cells. Further, technology of layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) may be used for enabling the cell switch. LTM is a procedure in which the next generation node B (gNB) receives layer 1 (LI) and / or layer 3 (L3) measurement report(s) from a UE, and thus the gNB changes user equipment (UE) serving cell by a cell switch command signaled via a medium access control (MAC) control element (CE). The LTM procedure may be used to reduce the mobility latency.SUMMARY

[0004] In a first aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storinginstructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus; perform a random access channel-less access to a third apparatus of the at least one candidate apparatus; and transmit data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0005] In a second aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; receive, from the fourth apparatus, the configured grant; and transmit, to a first apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

[0006] In a third of the present disclosure, there is provided a fourth apparatus. The fourth apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the fourth apparatus to: receive, from a second apparatus, a request for a configured grant for a key of the fourth apparatus; transmit, to the second apparatus, the configured grant; and receive data from a first apparatus on the configured grant based on the key of the fourth apparatus.

[0007] In a fourth aspect of the present disclosure, there is provided a method. The method comprises: receiving, at a first apparatus and from a second apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus; performing a RACH-less access to a third apparatus of the at least one candidate apparatus; and transmitting data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0008] In a fifth aspect of the present disclosure, there is provided a method. The method comprises: transmitting, from a second apparatus and to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; receiving, from the fourth apparatus, the configured grant; and transmitting, to a first apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

[0009] In a sixth aspect of the present disclosure, there is provided a method. Themethod comprises: receiving, at a fourth apparatus and from a second apparatus, a request for a configured grant for a key of the fourth apparatus; transmitting, to the second apparatus, the configured grant; and receiving data from a first apparatus on the configured grant based on the key of the fourth apparatus.

[0010] In a seventh aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for receiving, from a second apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus; means for performing a RACH-less access to a third apparatus of the at least one candidate apparatus; and means for transmitting data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0011] In an eighth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for transmitting, to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; means for receiving, from the fourth apparatus, the configured grant; and means for transmitting, to a first apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

[0012] In a ninth aspect of the present disclosure, there is provided a fourth apparatus. The fourth apparatus comprises means for receiving, from a second apparatus, a request for a configured grant for a key of the fourth apparatus; means for transmitting, to the second apparatus, the configured grant; and means for receiving data from a first apparatus on the configured grant based on the key of the fourth apparatus.

[0013] In a tenth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to any of the fourth to sixth aspects.

[0014] In some or all examples of the first to tenth aspects, the first apparatus may be further caused to, in response to receiving a cell switch command indicating to switch to the third apparatus, generate the key of the fourth apparatus; and perform a RACH-less access to the fourth apparatus by transmitting the data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0015] In some example embodiments, the configuration may be comprised in a radio resource control (RRC) reconfiguration message. In some example embodiments, the LTM configuration may indicate that the configured grant is used for an inter-master node (MN) cell switch or an inter-centralized unit (CU) cell switch. In some example embodiments, the cell switch may comprise an inter- master node MN LTM cell switch or an inter-centralized unit CU LTM cell switch.

[0016] In some example embodiments, the first apparatus may be in a dual connectivity with the fourth apparatus.

[0017] It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0019] FIG. 1 illustrates example communication environment in which example embodiments of the present disclosure can be implemented;

[0020] FIG. 2 illustrates a signaling flow for a cell switch procedure with a random access channel based procedure;

[0021] FIG. 3 illustrates a signaling flow for cell switch procedure in accordance with some example embodiments of the present disclosure;

[0022] FIG. 4 illustrates another signaling flow for cell switch procedure in accordance with some example embodiments of the present disclosure;

[0023] FIG. 5A and FIG. 5B illustrate another signaling flows for cell switch procedure in accordance with some example embodiments of the present disclosure, respectively;

[0024] FIG. 6 illustrates another signaling flow for cell switch procedure in accordance with some example embodiments of the present disclosure;

[0025] FIG. 7A and FIG. 7B illustrate further example signaling flows for cell switch procedure in accordance with some example embodiments of the present disclosure;

[0026] FIG. 8 illustrates a flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0027] FIG. 9 illustrates a flowchart of a method implemented at a second apparatus in accordance with some example embodiments of the present disclosure;

[0028] FIG. 10 illustrates a flowchart of a method implemented at a fourth apparatus in accordance with some example embodiments of the present disclosure;

[0029] FIG. 11 illustrates another flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0030] FIG. 12 illustrates another flowchart of a method implemented at a second apparatus in accordance with some example embodiments of the present disclosure;

[0031] FIG. 13 illustrates another flowchart of a method implemented at a fourth apparatus in accordance with some example embodiments of the present disclosure;

[0032] FIG. 14 illustrates another flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0033] FIG. 15 illustrates another flowchart of a method implemented at a secpmd apparatus in accordance with some example embodiments of the present disclosure;

[0034] FIG. 16 illustrates a flowchart of a method implemented at a fourth apparatus in accordance with some example embodiments of the present disclosure;

[0035] FIG. 17 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0036] FIG. 18 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0037] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0038] 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 limitation as to the scope of the disclosure.Embodiments described herein can be implemented in various manners other than the ones described below.

[0039] 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.

[0040] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0041] It shall be understood that although the terms “first,” “second,”..., etc. in front of noun(s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun(s). For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0042] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0043] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0044] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0045] As used in this application, the term “circuitry” may refer to one or more or all of the following:(a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and(b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and / or digital hardware circuit(s) with software / firmware and(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0046] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0047] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA),High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, 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), 5.5G, the sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0048] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture comprises a CU and a Distributed Unit (DU) at an IAB donor node. An IAB node comprises a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the nexthop IAB node.

[0049] As used herein, the term “core network function” may be implemented as a core network entity that includes a combination of hardware processing circuit and software and / or firmware comprising machine-readable instructions, or software comprising machine-readable instructions that are executable by at least one processor of hardware processing circuit of an apparatus. A hardware processing circuit includes at least one processor and at least one memory storing machine-readable instructions that are executable by the at least one processor of the hardware processing circuit. A processorincludes any or some combination of an accelerator, a microprocessor, a core of a multicore microprocessor, a microcontroller, a programmable integrated circuit, a programmable gate array, a digital signal processor, a central processing unit, a graphic processing unit, a tensor processing unit. Memory includes any or some combination of volatile or non-volatile memory (e.g., a flash memory, cache, a random-access memory (RAM), and / or a read-only memory (ROM)). The memory stores the machine-readable instructions of the software and / or firmware for execution by the at least one processor of the hardware processing circuit. The machine-readable instructions are executable by the at least one processor of the hardware processing circuit cause the hardware processing circuit to perform the actions or operations of the methods described herein. For example, the session management function described herein may be implemented as a session management entity and the session management policy control function described herein may be implemented as a session management policy control entity, respectively.

[0050] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0051] As used herein, the term “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other combination of the time, frequency, space and / or code domain resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.Example Environment

[0052] FIG. 1 shows an example communication environment 100 in which example embodiments of the present disclosure may be implemented. The network communication 100 includes a plurality of apparatuses, such as a first apparatus 110, a second apparatus 120, a third apparatuses 130 and a fourth apparatus 140.

[0053] In some example embodiments, the first apparatus 110 may be comprised in a terminal device / apparatus and the second apparatus 120 / third apparatus 130 / fourth apparatus 140 may be comprised in a network device / apparatus. Additionally, the second apparatuses 120 and the third apparatus 130 may provide one or more coverage areas, also called as cells. As illustrated in FIG. 1, the communication environment 100 includes a cell 150 provided by the second apparatus 120 and a cell 160 provided by the second apparatus 120 provided by the third apparatus 130. It is to be understood that the fourth apparatus 140 may also provide a coverage area or cell (not shown).

[0054] Further, in some example embodiments, the radio access network (RAN) architecture may include a centralized part, or CU, and a distributed part, or distributed unit (DU). The CU and the DU may be connected to one another by a so-called Fl interface. In the example of FIG. 1, the second apparatus 120 may refer to a base station (such as, the next generation node B, gNB), a gNB-CU and / or a gNB-DU. Similarly, the third apparatus 130 also may refer to a base station (such as, a gNB), a gNB CU and / or a gNB DU.

[0055] In the example of FIG. 1, the first apparatus 110 may move over time. Asillustrated in FIG. 1, the first apparatus 110 locates at different positions at different time points (T1 and T2). As moving, the first apparatus 110 may switch among different cells, i.e., a cell switch procedure. In the example of FIG. 1, the first apparatus 110 may switch from the cell 150 to the cell 160. For a better discussion, the cell 150 may be called as the source cell 150 or the serving cell 150, and the cell 160 may be called as the candidate cell 160. Further, in a case that the cell 160 is selected as a target cell, the cell 160 also may be called as the target cell 160. The second apparatus 120 may be referred to as a source apparatus or source gNB, and the third apparatus 130 may be referred to as a candidate / target apparatus or candidate / target gNB.

[0056] In some example embodiments, the first apparatus 110 supports a new radio-dual connectivity (NR-DC). As illustrated, at Tl, the first apparatus 110 connects with the second apparatus 120 and in DC with the fourth apparatus 140. That is, the second apparatus 120 performs as a master node (MN) and the fourth apparatus 140 performs as a secondary node (SN). The second apparatus 120 (that is, the MN) provides a primary cell (the cell 150) and may include a radio resource controlling unit for the first apparatus 110. The fourth apparatus 140 may provide a secondary cell (not shown) for the first apparatus 110. At T2, the first apparatus 110 connects with the third apparatus 130 and in DC with the fourth apparatus 140. As used herein, the second apparatus 120 may also be referred to as a source MN, the third apparatus 130 may also be referred to as a candidate / target MN, and the fourth apparatus 140 may be referred to as an SN. In such embodiments, a cell switch from the cell 150 of the second apparatus 120 to the cell 160 of the third apparatus 130 may be referred to as an “inter-MN cell switch”.

[0057] In some example embodiments, the second apparatus 120 and the third apparatus 130 are gNB DUs connecting to two different gNB-CUs. A cell switch from the cell 150 of the second apparatus 120 to the cell 160 of the third apparatus 130 may be referred to as an “inter-CU cell switch”. As used herein, the term “inter-CU” may refer to the interactions and handovers occurring between different centralized units within a mobile communication network. CUs are network nodes responsible for handling higher-layer functions such as radio resource control and mobility management. The term “inter-CU cell switch” specifically pertains to the processes, procedures, and mechanisms involved when a UE transitions from one CU to another, ensuring continuous and seamless connectivity during the handover. The cell switch discussed herein may include at least one of the following: an inter-gNB cell switch, an inter-MN cell switch, or an inter-CUcell switch.

[0058] In some example embodiments, a transmission direction from the second apparatus 120 / third apparatus 130 / fourth apparatus 140 to the first apparatus 110 is referred to as a downlink (DL), while a transmission direction from the first apparatus 110 to the second apparatus 120 / third apparatus 130 / fourth apparatus 140 is referred to as an uplink (UL). In DL, the second apparatus 120 / third apparatus 130 / fourth apparatus 140 is a transmitting (TX) device (or a transmitter) and the first apparatus 110 is a receiving (RX) device (or a receiver). In UL, the first apparatus 110 is a TX device (or a transmitter) and the second apparatus 120 / third apparatus 130 / fourth apparatus 140 is a RX device (or a receiver).

[0059] It is to be understood that the number of devices and their connections shown in FIG. 1 are only for the purpose of illustration without suggesting any limitation. The communication environment 100 may include any suitable number of devices configured to implement example embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be located in the cell, and one or more additional cells may be deployed in the communication environment 100. It is noted that although illustrated as a network device, the second apparatus 120 / the third apparatus 130 / the fourth apparatus 140 may be another device than a network device. Although illustrated as a terminal device, the first apparatus 110 may be another device than a terminal apparatus.

[0060] Communications in the communication environment 100 may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.

[0061] In some mechanisms, on inter MN handover (HO) with DC active, MN master key gets changes. If the master key is changes, the MN needs to regenerate SN-key(s). That is, the SN key changes too.

[0062] FIG. 2 illustrates a signaling flow 200 for a cell switch procedure with a RACH based procedure. The signaling flow 200 involves a UE 201, a gNB 202 (referred to as a source gNBl or an MN1), a gNB 203 (referred to as a candidate gNB2 or an MN2), a gNB 204 (referred to a candidate gNB4 or an MN3), a gNB 205 (referred to a gNB3 or a SN1) and an optional access and a mobility management function (AMF) 206.

[0063] In FIG. 2, the UE 201 is in the NR-DC with the gNB 205 (that is, the SN1). The gNB 202 (that is, the MN1) shares a security key counter (SK-counter) with the UE 201 as well as with the SN during DC configuration. As illustrated, step 17 involves RACH access and there will be interruption for SCG bearers due to RACH access.

[0064] In steps 2-9, the UE 201 sends L3 measurement report for LTM configuration. The source MN takes the decision to prepare the LTM candidates and sends Handover request to the target MN. On receiving Handover request Acknowledgement, the source MN prepares RRC Reconfiguration containing LTM configurations and sends to the UE 201.

[0065] In step 10, the UE 201 sends LI measurement report to the MN 1 (that is, a serving DU). The serving MN initiates an inter CU LTM Cell Switch to the MN2.

[0066] In steps 11-12, the serving MN sends a Cell Switch Command to the UE 201 to perform an inter CU LTM handover to the MN2. The UE 201 on receiving the Cell Switch Command generates a new MN key. It also generates a new SN key by using the SK- counter and the generated new MN key.

[0067] In steps 13-14, the source MN sends a Cell Switch Notification to the target MN. The target MN generates the new SN keys and shares the generated new SN kyes with the SN.

[0068] In step 15, the UE 201 performs RACH less access to the target MN as configured grant is shared to the UE 201 by network for target MN access.

[0069] In steps 16-18, as the SN key changed due to inter MN handover, the UE 201 performs RACH based access with the SN to apply the new SN key. The SN after successful RACH access uses the new SN key for subsequent packets.

[0070] In step 19, the network performs the handover completion procedures.

[0071] To sum up, upon HO to the target MN, the UE starts using the new mater key on successfully access to the target MN. Upon the inter MN Handover, the UE performs RACH less access to the target MN by using configured grant or static grant. As the SN- key changes during the inter MN Handover, the UE performs the RACH based procedure with the SN to start using the new SN key. This adds interruption in data transmission through secondary cell group (SCG). Since LTM is meant to reduce the time to access the network upon handover, but the RACH based access to the SN after handover will add a delay to data transmission in SCG leg.Work Principle and Example Signalling for Communication

[0072] In order to solve at least part of the above problems or other potential problems, several solutions on cell switch procedure such as an LTM cell switch are proposed. In a solution, a second apparatus such as a target gNB or target MN requests a configured grant for a key of a fourth apparatus such as an SN from the fourth apparatus. The second apparatus then transmits, to a first apparatus such as a terminal device, a cell switch command indicating to switch to a third apparatus such as a target gNB or target MN. The cell switch command includes an indication of the configured grant for the key of the fourth apparatus. The first apparatus performs a RACH-less access to the third apparatus. The first apparatus transmits data to the fourth apparatus on the configured grant based on the key of the fourth apparatus. In this manner, the first apparatus may transmit data to the SN on the indicated configured grant using the key of the SN, without performing a RACH-based access procedure to the SN. The time delay of the data transmission due to the RACH-based access can thus be reduced.

[0073] In another solution, the second apparatus such as the target gNB or target MN requests the configured grant for the key of the fourth apparatus such as the SN from the fourth apparatus. The second apparatus then transmits, to the first apparatus such as a terminal device, an LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus. The first apparatus performs a RACH-less access to a third apparatus of the at least one candidate apparatus. The first apparatus transmits data to the fourth apparatus on the configured grant based on the key of the fourth apparatus. In this manner, the first apparatus may transmit data to the SN on the indicated configured grant using the key of the SN, without performing a RACH-basedaccess procedure to the SN. The time delay of the data transmission due to the RACH- based access can thus be reduced.

[0074] In a further solution, the second apparatus such as the target gNB or the target MN requests a configuration for updating at least one DRB of the fourth apparatus from the fourth apparatus. The second apparatus then transmits, to the first apparatus, the configuration for updating at least one DRB of the fourth apparatus. The configuration indicates a mapping between at least one logical channel and the at least one DRB. In response to receiving a cell switch command to switch to a third apparatus, the first apparatus generates the key of the fourth apparatus. The first apparatus updates the at least one DRB based on the configuration, and transmits data to the fourth apparatus on the at least one updated DRB based on the key of the fourth apparatus. In this manner, the first apparatus may transmit data to the SN on the updated DRB using the key of the SN, without performing a RACH-based access procedure to the SN. The time delay of the data transmission due to the RACH-based access can thus be reduced.

[0075] Several solutions of the present disclosure have been briefly described. Principle and implementations of the present disclosure will be described in detail below with reference to FIGS. 3-18. It is noted the order acts shown in FIG. 3-16 are only an example not limitation. Acts may be performed in any suitable manner. Example embodiments described with reference to FIG. 3 to FIG. 16 may be implemented separately or combined in any manner. For example, one or more example embodiments shown in a single drawing may be combined with one or more example embodiments shown in one or more other drawings. It should be noted that the steps as illustrated in one or more drawings may be selectively performed in an actual implementation.

[0076] In the following discussion, the cell switch may comprise at least one of the following: an inter-gNB cell switch, an inter-MN cell switch such as inter-MN LTM cell switch, or an inter-CU cell switch such as inter-CU LTM cell switch.

[0077] Further, in the following discussions, the first apparatus 110 may include a terminal device, the second apparatus 120 may include one of the following: a gNB or MN serving the first apparatus 110, a DU connecting with the first apparatus 110, or a CU connecting with the DU, the third apparatus 130 may include one of the following: a target gNB or MN, a target DU, or a target CN, and the fourth apparatus 140 may include an SN in a DC with the first apparatus 110.

[0078] FIG. 3 illustrates a signaling flow 300 for cell switch procedure in accordance with some example embodiments of the present disclosure. The signaling flow 300 involves the first apparatus 110, the second apparatus 120, the third apparatus 130 and the fourth apparatus 140 in FIG. 1.

[0079] In operation, the second apparatus 120 transmits (310), to the fourth apparatus 140, a request for a configured grant for a key of the fourth apparatus 140. The fourth apparatus 140 receives (320) the request. The key of the fourth apparatus 140 may be a new key to be generated by the first apparatus 110 and / or the third apparatus 130. As used herein, the configured grant for the key of the fourth apparatus 140 may be referred to as “configured grant for SN key update / refresh” or “SN key update / refresh configured grant”. The configured grant may indicate a resource for data transmission using the key of the fourth apparatus 140. For example, the configured grant towards the first apparatus 110 may include a resource location and periodicity of the configured grant.

[0080] As an example, the request for the configured grant may be transmitted (310) to the fourth apparatus 140 at a time point before transmitting a configuration of LTM to the first apparatus 110. As an alternative example, the request for the configured grant may be transmitted (310) to the fourth apparatus 140 at a time point after receiving a measurement report from the first apparatus 110 and before transmitting a cell switch command to the first apparatus 110. For example, the configured grant request for RACH less SN key refresh with SN may be performed closer to the cell Switch command. In this manner, the configured grant for SN key may be requested and obtained at different time points.

[0081] In response to receiving (320) the request, the fourth apparatus 140 transmits (330) the configured grant for the key to the second apparatus 120. The second apparatus 120 receives (340) the configured grant for the key. In some example embodiments, upon inter MN LTM preparation, the second apparatus 120 such as a source MN may request the fourth apparatus 140 such as an SN for configured grant and share the configured grant received from the SN to the first apparatus 110. The configured grant for the key may not be used for other usage. That is, the first apparatus 110 may not be expected to use the configured grant for other data transmission.

[0082] The second apparatus 120 transmits (350), to the first apparatus 110, a cell switch command indicating to switch to the third apparatus 130. The first apparatus 110receives (360) the cell switch command. The cell switch command includes an indication of the configured grant for the key. As an example, the cell switch command may include the configured grant for SN key shared by the fourth apparatus 140. As another example, the cell switch command may include an indication to apply the configured grant for the key received in a further message. For example, the configured grant for the key may be included in an RRC message such as LTM configuration message from the second apparatus 120. The cell switch command may indicate to use the configured grant included in the RRC message. By way of example, the configured grant may be included in a MAC CE, or any other suitable message or signaling.

[0083] In response to receiving (360) the cell switch command, the first apparatus 110 performs a RACH-less access to the third apparatus 130. The first apparatus 110 transmits (380) data to the fourth apparatus 140 on the configured grant based on the key of the fourth apparatus 140.

[0084] In some embodiments, in response to receiving (360) the cell switch command, the first apparatus 110 may generate the key of the fourth apparatus 140. The generated key may be referred to as a new SN key. The first apparatus 110 may perform a RACH- less access to the fourth apparatus 140 by transmitting the data to the fourth apparatus 140 on the configured grant using the key of the fourth apparatus 140. That is, upon receiving (360) the cell switch command, the first apparatus 110 switches to the target MN and uses the received configured grant to send (380) data (referred to as first data used herein) to the fourth apparatus 140 using the new SN key. In this way, the first apparatus 110 uses the SN configured grant to perform the RACH-less SN access after the inter CU LTM handover. The time delay of data transmission due to RACH-based access to SN can thus be reduced.

[0085] In response to receiving (390) the data on the configured grant, the fourth apparatus 140 may apply the key for a transmission with the first apparatus 110. In some example embodiments, the configured grant for the key is not initially activated at the fourth apparatus 140. In an example embodiment, the second apparatus 120 may transmit an indication for activating the configured grant to the fourth apparatus 140. For example, the indication for activating the configured grant may be included in a secondary node modification request to the fourth apparatus 140.

[0086] Alternatively, in an example embodiment, the second apparatus 120 may transmitan indication for activating the configured grant to the third apparatus 130. For example, the indication may be included in a cell switch notification of to the third apparatus 130. In response to receiving the cell switch notification, the third apparatus 130 may indicate the fourth apparatus 140 to activate the configured grant. For example, the third apparatus 130 may transmit a secondary node modification request to the fourth apparatus 140, indicating to activate the configured grant. In this way, the fourth apparatus 140 may be informed about when to activate the configured grant. The SN configured grant during inter CU-LTM may be optionally activated.

[0087] FIG. 4 illustrates another signaling flow 400 for cell switch procedure in accordance with some example embodiments of the present disclosure. The signaling flow 400 involves the first apparatus 110, the second apparatus 120, the third apparatus 130 and the fourth apparatus 140 in FIG. 1.

[0088] In operation, the second apparatus 120 transmits (410), to the fourth apparatus 140, a request for a configured grant for a key of the fourth apparatus 140. The fourth apparatus 140 receives (420) the request. The key of the fourth apparatus 140 may be a new key to be generated by the first apparatus 110 and / or the third apparatus 130. As an example, the request for the configured grant may be transmitted (410) to the fourth apparatus 140 at a time point before transmitting a configuration of LTM to the first apparatus 110.

[0089] In response to receiving (420) the request, the fourth apparatus 140 transmits (430) the configured grant for the key to the second apparatus 120. The second apparatus 120 receives (440) the configured grant for the key. In some example embodiments, upon inter MN LTM preparation, the second apparatus 120 such as a source MN may request the fourth apparatus 140 such as an SN for configured grant and share the configured grant received from the SN to the first apparatus 110. The configured grant for the key may not be used for other usage. That is, the first apparatus 110 may not be expected to use the configured grant for other data transmission.

[0090] The second apparatus 120 transmits (450), to the first apparatus 110, an LTM configuration (also referred to as a configuration of LTM). The first apparatus 110 receives (460) the LTM configuration. The LTM configuration indicates at least one candidate apparatus and the configured grant for the key of the fourth apparatus 140. It is to be understood that the LTM configuration may include further information regardingLTM, for example, MN configuration and / or SN configuration. The configured grant for the key may be included in the MN configuration and / or SN configuration. The LTM configuration or any other related message may indicate that the configured grant is to be used for inter-MN master cell group (MCG) cell switch and / or used for SN key update / refresh. The LTM configuration may be included in an RRC configuration (or reconfiguration) message or any other suitable message or signaling. The RRC configuration message may include the configured grant towards the first apparatus 110 that includes resource location and periodicity of the configured grant.

[0091] The first apparatus 110 performs a RACH-less access to the third apparatus 130 of the at least one candidate cell. The first apparatus 110 transmits (480) data to the fourth apparatus 140 on the configured grant based on the key of the fourth apparatus 140. In this way, the first apparatus 110 uses the SN configured grant to perform the RACH- less SN access after the inter CU LTM handover. The time delay of data transmission due to RACH-based access to SN can thus be reduced.

[0092] In some embodiments, the second apparatus may transmit, to the first apparatus 110, a cell switch command indicating to switch to the third apparatus 130. In response to receiving the cell switch command, the first apparatus 110 performs the RACH-less access to the third apparatus 130.

[0093] In response to receiving the cell switch command, the first apparatus 110 may generate the key of the fourth apparatus 140. The first apparatus 110 may perform the RACH-less access to the fourth apparatus 140 by transmitting the data to the fourth apparatus 140 on the configured grant using the key of the fourth apparatus 140. That is, upon receiving the cell switch command, the first apparatus 110 switches to the target MN and uses the received configured grant to send data (referred to as first data used herein) to the fourth apparatus 140 using the new SN key.

[0094] In response to receiving (490) the data on the configured grant, the fourth apparatus 140 may apply the key for a transmission with the first apparatus 110. Upon receiving (490) the data on the configured grant which is indicated to the first apparatus 110 to use after the inter MN LTM cell switch and for SN key refresh, the fourth apparatus 140 may apply the new SN key.

[0095] In some example embodiments, the configured grant for the key is not initially activated at the fourth apparatus 140. In an example embodiment, the second apparatus120 may transmit an indication for activating the configured grant to the fourth apparatus 140. For example, the indication for activating the configured grant may be included in a secondary node modification request to the fourth apparatus 140. Alternatively, in an example embodiment, the second apparatus 120 may transmit an indication for activating the configured grant to the third apparatus 130. For example, the indication may be included in a cell switch notification of to the third apparatus 130. In response to receiving the cell switch notification, the third apparatus 130 may indicate the fourth apparatus 140 to activate the configured grant. For example, the third apparatus 130 may transmit a secondary node modification request to the fourth apparatus 140, indicating to activate the configured grant.

[0096] Several example embodiments for cell switch procedure with the configured grant for SN key refresh have been described with respect to FIG. 3 and FIG. 4. In some example embodiments, these embodiments may be applied separately, or in combination. Further embodiments for cell switch procedure with the configured grant for SN key refresh will be described with respect to FIG. 5A and FIG. 5B, which illustrate another signaling flows 500 and 550 for cell switch procedure with configured grant for inter-MN LTM with SCG unchanged in accordance with some example embodiments of the present disclosure. The signaling flows 500 and 550 involve a UE 501, a gNB 502 (referred to as a source gNBl or an MN1), a gNB 503 (referred to as a candidate gNB2 or an MN2), a gNB 504 (referred to a candidate gNB4 or an MN3), a gNB 505 (referred to a gNB3 or an SN1) and an optional AMF 506. The UE 501 may be an example implementation of the first apparatus 110 in FIG. 1, the gNB 502 may be an example implementation of the second apparatus 120 in FIG. 1, the gNB 503 and the gNB 504 may be example implementations of the third apparatus 130 in FIG. 1, and the gNB 505 may be an example implementation of the fourth apparatus 140 in FIG. 1.

[0097] In operation, the UE 501 is connected to the MN (for example, the gNB 502) and is in the NR-DC with the SN (for example, the gNB 505).

[0098] In steps 2, the UE 501 may send a layer 3 (L3) measurement report to configure LTM candidates. In step 3, the gNB 502 (that is, the source MN) may decide to prepare inter CU LTM candidates. In step 4 or 6, the gNB 502 may send a Handover request to potential target MNs (such as the gNB 503 and the gNB 504) for an inter MN LTM preparation. In step 5 or 7, the gNB 502 may receive a handover request acknowledge from the potential target MNs such as the gNB 503 and the gNB 504.

[0099] In steps 8, the gNB 502 requests the gNB 505 for configured grant by performing SN Modification Request procedure. In step 9, in response to receiving an SN modification request, the gNB 505 transmits an SN modification request acknowledge to the gNB 502. The SN modification request acknowledge includes the configured grant. The gNB 505 may allocate the configured grant to be used only during the inter MN handover to perform a RACH less access with the gNB 505 to change the new SN security key usage. Alternately, the SN configured grant may be activated during cell switch. Thes steps may be performed closer to cell switch (shown in step 14) when cell switch command includes SN grant for SN key change.

[0100] In step 10, as an alternate 510, a CU of the gNB 502 shares the CG with the UE 501 in RRC Reconfiguration (such as an LTM preparation configuration). As shown in step 11, the gNB 502 includes the SN configured grant allocated for SN key change in an RRC Reconfiguration containing the LTM configurations. The UE 501 uses the configured grant on inter-CU handover. As an alternate 520, the CU shares a CG indication for SN key refresh with a source DU and the source DU indicates the use CG in a cell switch command to the UE 501 during the inter CU LTM. The MN may indicate the use of SN configured grant that’s sent to the UE 501 in RRC Reconfiguration during the inter CU LTM handover.

[0101] In step 13, the UE 501 may send an LI measurement report. The gNB 502 may decide to perform an inter CU LTM cell switch.

[0102] In step 14 in the signaling flow 550, as an alternate to step 8-9, the SN configured grant, for the RACH less SN access to use the new SN key, is requested by performing operations similar to those of steps 8 and 9 closer to a cell switch command. For example, the SN modification request and the SN modification request acknowledge may be transmitted when an inter CU timing advance (TA) acquisition started. In such alternate, the SN configured grant is shared in the cell switch command during the inter CU-LTM HO.

[0103] In step 15, the gNB 502 such as the source MN or the source DU sends the cell switch command to UE 501. The cell switch command optionally may include SN configured grant indication. In step 16, the UE 501 on receiving the cell switch command, may generate a new MN security key. The UE 501 may also generate the SN key by using the new MN key and SK-counter.

[0104] In an alternate 560, in step 18, the gNB 502 may sends a cell switch notification to the target MN with an activation flag for the SN configured grant. In step 19, the SN key may change due to the inter MN LTM HO. The target MN may generate the new SN keys for the configured SK-counters. In step 20, the target MN such as the gNB 503 may send an SN Modification Request to activate the configured grant allocated by the SN for SN RACH less access to change the use of new SN key. The gNB 505 may respond with an SN modification request acknowledge (ACK).

[0105] Alternately, in an alternate 570, in step 23, the gNB 502 may also indicate the SN to activate the configured grant allocated by the SN for the SN RACH less access to change the use of new SN key. For example, the gNB 502 may transmit an SN modification request to the gNB 505. Likewise, in step 24, the gNB 505 may respond with an SN modification request ACK.

[0106] In step 25, the UE 501 performs the RACH less access to target MN as configured grant is shared to UE 501 by network for target MN access.

[0107] In step 26, the UE 501 performs the RACH less SN key change by sending the first data on using the configured grant received from SN for SN RACH less access. For example, in step 27, the UE 501 transmits the first data on the configured grant using the new SN key. In step 28, the SN on receiving the data on configured grant changes to start to use the new SN key.

[0108] In step 29, the UE 501 may perform handover completion procedures.

[0109] With the signaling flows 500 and 550, the UE uses the SN configured grant to perform the RACH less SN access after the inter-CU LTM handover. The SN configured grant may be optionally activated during the inter-CU LTM. In this manner, RACH- based access to SN is not needed. The delay resulting from the RACH-based access to SN can be reduced.

[0110] FIG. 6 illustrates another signaling flow 600 for cell switch procedure in accordance with some example embodiments of the present disclosure. The signaling flow 600 involves the first apparatus 110, the second apparatus 120, the third apparatus 130 and the fourth apparatus 140 in FIG. 1.[OHl] In operation, the second apparatus 120 transmits (610), to the fourth apparatus 140, a request for a configuration for updating at least one DRB of the fourth apparatus140. In response to receiving (620) the request, the fourth apparatus 140 transmits (630), to the second apparatus 120, the configuration indicating a mapping between at least one logical channel and the at least one DRB. The second apparatus 120 receives (640) the configuration. As used herein, the configuration for updating the at least one DRB may be referred to as “DRB update configuration” or “DRB configuration” or “delta DRB configuration”.

[0112] In some example embodiments, the fourth apparatus 140 may prepare new DRB(s) for existing DRB(s). The fourth apparatus 140 may map the new DRB(s) with corresponding new logical channel(s). The DRB update configuration may include delta configuration for the new DRB(s). In other words, the DRB update configuration may indicate a difference between a second DRB configuration and a first DRB configuration. The second DRB configuration (that is, the new DRB configuration) may be used for an inter-MN LTM cell switch or an inter-CU LTM cell switch, and the first DRB configuration (that is, a previous DRB configuration) may be applied before the cell switch. The DRB update configuration may include at least one identifier (ID) of the at least one DRB and at least one ID of at least one channel (such as logical channel ID (LCID)) associated with the at least one DRB. In this way, the difference or delta DRB configuration instead of the whole DRB configuration may be transmitted. The signaling overhead can thus be reduced.

[0113] In some example embodiments, for SCG part of the configuration, new SCG configuration (such as an RRC configuration) may be included when inter MN master cell group (MCG)-LTM is configured for MN. The configuration may use different DRB- IDs and LCIDs for the current DRBs.

[0114] The second apparatus 120 transmits (650) the DRB update configuration to the first apparatus 110. The first apparatus 110 receives (660) the DRB update configuration. In some example embodiments, the DRB update configuration may be included in an LTM configuration indicating at least one candidate apparatus, or other RRC reconfiguration message or any other suitable message or signaling.

[0115] The second apparatus 120 transmits (670) a cell switch command to switch to the third apparatus 130 to the first apparatus 110. In response to receiving (680) the cell switch command, the first apparatus 110 generates (690) the key of the fourth apparatus 140. The first apparatus 110 updates (692) the at least one DRB based on theconfiguration. The first apparatus 110 transmits (694) data to the fourth apparatus 140 on the at least one updated DRB based on the generated key of the fourth apparatus 140. The fourth apparatus 140 receives (696) the data from a first apparatus 110 on the at least one updated DRB using the key of the fourth apparatus 140. For example, on MCG cell switch, the first apparatus 110 switches to the new DRB configuration and uses new key for the new DRB(s). In this manner, the RACH-based access to the fourth apparatus 140 is not needed. The time delay for data transmission can be reduced.

[0116] In some example embodiments, in response to receiving (696) the data on the at least one updated DRB, the fourth apparatus 140 may apply the key for a transmission with the first apparatus 110 on the at least one updated DRB.

[0117] In some example embodiments, the second apparatus 120 may transmit an indication for activating the at least one updated DRB to the fourth apparatus 140. For example, the indication for activating the at least one updated DRB may be included in a secondary node modification request to the fourth apparatus 140.

[0118] Alternatively, or in addition, in some example embodiments, the second apparatus 120 may transmit an indication for activating the at least one updated DRB to the third apparatus 130. For example, the indication for activating the at least one updated DRB may be included in a cell switch notification of to the third apparatus 130. In response to receiving the cell switch notification, the third apparatus 130 may transmit a message such as a secondary node modification request to the fourth apparatus 140, to activate the at least one updated DRB.

[0119] In response to receiving the indication for activating the at least one updated DRB, the fourth apparatus 140 may update the at least one DRB based on the configuration. In this way, the MN (source MN or target MN) may inform the SN to activate the new configuration when it executes the MN cell switch.

[0120] Several example embodiments for cell switch procedure with DRB update have been described with respect to FIG. 6. Further embodiments for cell switch procedure with DRB update will be described with respect to FIG. 7A and FIG. 7B, which illustrate further example signaling flows 700 and 750 for cell switch procedure in accordance with some example embodiments of the present disclosure. The signaling flows 700 and 750 involve the UE 501, the gNB 502 (referred to as a source gNBl or MN1), the gNB 503 (referred to as a candidate gNB2 or MN2), the gNB 504 (referred to a candidate gNB4 orMN3), the gNB 505 (referred to a gNB3 or SN1) and the optional AMF 506. The UE 501 may be an example implementation of the first apparatus 110 in FIG. 1, the gNB 502 may be an example implementation of the second apparatus 120 in FIG. 1, the gNB 503 and the gNB 504 may be example implementations of the third apparatus 130 in FIG. 1, and the gNB 505 may be an example implementation of the fourth apparatus 140 in FIG. 1.

[0121] In operation, the UE 501 is connected to the gNB 502 (such as the MN1) and is in the NR-DC with the gNB 505 (such as the SN1).

[0122] In step 2, the UE 501 may send a layer 3 (L3) measurement report to configure LTM candidates. In step 3, the gNB 502 (that is, the source MN) may decide to prepare inter CU LTM candidates. In step 4 or 6, the gNB 502 may send a Handover request to potential target MNs (such as the gNB 503 and the gNB 504) for an inter MN LTM preparation. In step 5 or 7, the gNB 502 may receive a handover request acknowledge from the potential target MNs such as the gNB 503 and the gNB 504..

[0123] In step 8, the gNB 502 requests, the gNB 505 (that is, the SN) for a delta DRB configuration for existing DRBs at the SN for RACH less SN access by performing an SN modification request procedure. In step 9, the SN may configure the new DRBs and logical channels for all existing DRBs and share the delta DRB and logical channel configuration along with LCID and DRB mapping with the source MN. In step 10, in response to receiving an SN modification request, the gNB 505 transmits an SN modification request acknowledge to the gNB 502. The SN modification request acknowledge includes the delta DRB configuration.

[0124] In step 11, the gNB 502 includes the SN delta DRB configurations and logical channel configurations in RRC Reconfiguration along with target MN LTM candidate configurations. In step 12, the gNB 502 sends the RRC reconfiguration to UE 501. The RRC reconfiguration may contains an LTM target configuration, The gNB 502 includes the delta SN DRB and logical channel configuration including an LCID-DRB mapping in the LTM target configuration. In step 13, the UE 501 may respond an RRC reconfiguration complete to the gNB 502.

[0125] As shown in the signaling flow 750, in step 14, the gNB 502 such as the source MN on receiving an LI measurement Reports, may decide for LTM cell switch. In step 15, the gNB 502 sends a cell switch command to the UE 501 to perform an LTM handoverto the target MN2.

[0126] In step 16, the UE 501 on receiving the cell switch command, performs the cell switch to the target MN2 and sends the RRC reconfiguration complete to the target MN2.

[0127] In step 17, the gNB 502 (that is, the source MN) may send the cell switch notification to the target MN (for example, MN2). As an alternate 760, in step 18, the target MN may activate the use of new DRBs configured at the SN, for use only during the inter MN handover case, through an SN modification procedure. In step 19, the SN key may change due to the inter MN LTM HO. For example, the target MN may generate new SN keys for configured SK-Counters. In step 20, the SN on receiving the message, may activate the DRBs to receive the data from UE.

[0128] In steps 23, as an alternate 770, the gNB 502 (the source MN) may also send the DRB activation indication to the SN through the SN modification request procedure. In step 24, the SN on receiving the message, may activate the DRBs to receive the data from the UE 501.

[0129] In step 26, the UE 501 applies the new DRB and logical channel configurations. The UE 501 switches the DRBs to new DRBs for sending or receiving of the data by using new SN key.

[0130] In step 27, the SN may switch the DRBs to new DRBs and upon receiving the data on new DRB, may apply the new SN key keys. For example, on receiving the indication from the source MN or the target MN, the SN may switch to new DRB. The SN may apply the new SN key on data received on the new DRBS. As shown, in step 28, the SN receives a first data packet on the new DRB. Then, in step 29, the SN may start sending DL packets in the new DRB by using the new SN key. That is, the SN may start the DL data on the new DRBs by using the new SN key.

[0131] In step 30, the UE 501 may perform handover completion procedures.

[0132] With the signaling flows 700 and 750, a RACH less access by using delta for new DRB configuration during LTM preparation can be achieved. The time delay for data transmission due to RACH-based access to SN can be reduced.

[0133] It is to be understood that although the signaling flows 300, 400, 500, 550, 600, 700 and 750 are described with the inter-CU cell switch for LTM as an example, some embodiments described with respect to these signaling flows may also be applicable forany other suitable mobility or any other suitable cell switch. Scope of embodiments of the present disclosure is not limited here.

[0134] It would be appreciated that some example specifications, signaling flows and embodiments are provided above, and the detailed description may be varied. It is to be understood that these signaling flows 300, 400, 500, 550, 600, 700 and 750 may be used separately, or in any suitable combinations. With these embodiments, the inter-CU LTM cell switch procedure can be enhanced.Example Method

[0135] FIG. 8 shows a flowchart of an example method 800 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0136] At block 810, the first apparatus 110 receives, from a second apparatus, a cell switch command indicating to switch to a third apparatus, the cell switch command including an indication of a configured grant for a key of a fourth apparatus.

[0137] At block 820, the first apparatus 110 performs a RACH-less access to the third apparatus.

[0138] At block 830, the first apparatus 110 transmits data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0139] In some example embodiments, the first apparatus 110 may in response to receiving the cell switch command, generate the key of the fourth apparatus; and perform a RACH-less access to the fourth apparatus by transmitting the data to the fourth apparatus on the configured grant based on the key of the fourth apparatus. In this manner, the first apparatus 110 may perform the RACH-less access to the fourth apparatus by transmitting the data on the configured grant for the key using the generated key. The delay due to a RACH-based access to the fourth apparatus can be reduced.

[0140] In some example embodiments, the cell switch command is comprised in a MAC CE. Thus, the MAC CE cell switch command may indicate the configured grant for the key of the fourth apparatus.

[0141] In some example embodiments, the cell switch comprises an inter-MN LTM cellswitch or an inter-CU LTM cell switch. Thus, the cell switch procedure with configured grant for the key of the fourth apparatus may be applied for inter-MN LTM cell switch and / or inter-CU LTM cell switch.

[0142] FIG. 9 shows a flowchart of an example method 900 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 900 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0143] At block 910, the second apparatus 120 transmits, to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus.

[0144] At block 920, the second apparatus 120 receives, from the fourth apparatus, the configured grant.

[0145] At block 930, the second apparatus 120 transmits, to a first apparatus, a cell switch command indicating to switch to a third apparatus, the cell switch command including an indication of the configured grant.

[0146] In some example embodiments, the request for the configured grant is transmitted to the fourth apparatus at one of a time point before transmitting a configuration of LTM to the first apparatus, or a time point after receiving a measurement report from the first apparatus and before transmitting the cell switch command to the first apparatus. In this manner, the second apparatus 120 such as MN may share the SN configured grant with the first apparatus such as UE during a preparation for cell switch or during the cell switch.

[0147] In some example embodiments, the method 900 further comprises: transmitting an indication for activating the configured grant to at least one of the third apparatus, or the fourth apparatus. Thus, the configured grant may be optionally activated during the inter-CU LTM.

[0148] In some example embodiments, the indication is included in at least one of a cell switch notification of to the third apparatus, or a secondary node modification request to the fourth apparatus. The activation of the configured grant can thus be indicated by the second apparatus and / or the third apparatus.

[0149] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0150] FIG. 10 shows a flowchart of an example method 1000 implemented at a fourth apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of the fourth apparatus 140 in FIG. 1.

[0151] At block 1010, the fourth apparatus 140 receives, from a second apparatus, a request for a configured grant for a key of the fourth apparatus.

[0152] At block 1020, the fourth apparatus 140 transmits, to the second apparatus, the configured grant.

[0153] At block 1030, the fourth apparatus 140 receives data from a first apparatus on the configured grant based on the key of the fourth apparatus.

[0154] In some example embodiments, the method 1000 further comprises: in response to receiving the data on the configured grant, applying the key for a transmission with the first apparatus. In this way, the fourth apparatus 140 such as SN may apply the new SN key for following transmissions with the first apparatus.

[0155] In some example embodiments, the method 1000 further comprises: receiving an indication for activating the configured grant from at least one of: the second apparatus, or a third apparatus. In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus. In this manner, the fourth apparatus 140 such as SN allocates the configured grant for the key and optionally activates the configured grant during inter-CU LTM.

[0156] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0157] In some example embodiments, a first apparatus capable of performing any of the method 800 (for example, the first apparatus 110 in FIG. 1) may comprise means for performing the respective operations of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1.

[0158] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, a cell switch command indicating to switch to a third apparatus, the cell switch command including an indication of a configured grant for a key of a fourthapparatus; means for performing a RACH-less access to the third apparatus; and means for transmitting data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0159] In some example embodiments, the first apparatus further comprises: means for in response to receiving the cell switch command, generating the key of the fourth apparatus; and means for performing a RACH-less access to the fourth apparatus by transmitting the data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0160] In some example embodiments, the cell switch command is comprised in a MAC CE.

[0161] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0162] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0163] In some example embodiments, a second apparatus capable of performing any of the method 900 (for example, the second apparatus 120 in FIG. 1) may comprise means for performing the respective operations of the method 900. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1.

[0164] In some example embodiments, the second apparatus comprises means for transmitting, to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; means for receiving, from the fourth apparatus, the configured grant; and means for transmitting, to a first apparatus, a cell switch command indicating to switch to a third apparatus, the cell switch command including an indication of the configured grant.

[0165] In some example embodiments, the request for the configured grant is transmitted to the fourth apparatus at one of a time point before transmitting a configuration of MTL to the first apparatus, or a time point after receiving a measurement report from the first apparatus and before transmitting the cell switch command to the first apparatus.

[0166] In some example embodiments, the second apparatus further comprises: means for transmitting an indication for activating the configured grant to at least one of: thethird apparatus, or the fourth apparatus.

[0167] In some example embodiments, the indication is included in at least one of: a cell switch notification of to the third apparatus, or a secondary node modification request to the fourth apparatus.

[0168] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0169] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0170] In some example embodiments, a fourth apparatus capable of performing any of the method 1000 (for example, the fourth apparatus 140 in FIG. 1) may comprise means for performing the respective operations of the method 1000. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The fourth apparatus may be implemented as or included in the fourth apparatus 140 in FIG. 1.

[0171] In some example embodiments, the fourth apparatus comprises means for receiving, from a second apparatus, a request for a configured grant for a key of the fourth apparatus; means for transmitting, to the second apparatus, the configured grant; and means for receiving data from a first apparatus on the configured grant based on the key of the fourth apparatus.

[0172] In some example embodiments, the fourth apparatus may further comprise: means for in response to receiving the data on the configured grant, applying the key for a transmission with the first apparatus.

[0173] In some example embodiments, the fourth apparatus may further comprise: means for receiving an indication for activating the configured grant from at least one of: the second apparatus, or a third apparatus.

[0174] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0175] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0176] FIG. 11 shows a flowchart of another example method 1100 implemented at afirst apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1100 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0177] At block 1110, the first apparatus 110 receives, from a second apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus.

[0178] At block 1120, the first apparatus 110 performs a RACH-less access to a third apparatus of the at least one candidate apparatus.

[0179] At block 1130, the first apparatus 110 transmits data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0180] In some example embodiments, the first apparatus 110 may in response to receiving a cell switch command indicating to switch to the third apparatus, generate the key of the fourth apparatus; and perform a RACH-less access to the fourth apparatus by transmitting the data to the fourth apparatus on the configured grant based on the key of the fourth apparatus. In this manner, the first apparatus 110 can perform the RACH-less access to the fourth apparatus. The delay due to a RACH-based access to the fourth apparatus can be reduced.

[0181] In some example embodiments, the configuration is comprised in an RRC reconfiguration message. In this way, the RRC reconfiguration may include the configured grant towards the first apparatus that includes resource location and periodicity of the configured grant.

[0182] In some example embodiments, the LTM configuration indicates that the configured grant is used for an inter-MN cell switch or an inter-CU cell switch. For example, the cell switch may include an inter-MN LTM cell switch or an inter-CU LTM cell switch. That is, the cell switch procedure with the configured grant for the key can be applied to inter-CU cell switch and / or inter-MN cell switch.

[0183] FIG. 12 shows a flowchart of another example method 1200 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1200 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0184] At block 1210, the second apparatus 120 transmits, to a fourth apparatus, a requestfor a configured grant for a key of the fourth apparatus.

[0185] At block 1220, the second apparatus 120 receives, from the fourth apparatus, the configured grant.

[0186] At block 1230, the second apparatus 120 transmits, to a first apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

[0187] In some example embodiments, the LTM configuration is comprised in an RRC reconfiguration message.

[0188] In some example embodiments, the method 1200 further comprises: transmitting an indication for activating the configured grant to at least one of the fourth apparatus, or a third apparatus of the at least one candidate apparatus. In this way, the configured grant for the key of the fourth apparatus can be optionally activated.

[0189] In some example embodiments, the indication is included in at least one of a secondary node modification request to the fourth apparatus, or a cell switch notification of to the third apparatus. Therefore, the configured grant for the key of the fourth apparatus may be activated by the second apparatus and / or the third apparatus.

[0190] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch. Thus, the inter-MN LTM cell switch and / or the inter-CU LTM cell switch can be enhanced with the configured grant for the key of the fourth apparatus.

[0191] FIG. 13 shows a flowchart of another example method 1300 implemented at a fourth apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1300 will be described from the perspective of the fourth apparatus 140 in FIG. 1.

[0192] At block 1310, the fourth apparatus 140 receives, from a second apparatus, a request for a configured grant for a key of the fourth apparatus.

[0193] At block 1320, the fourth apparatus 140 transmits, to the second apparatus, the configured grant.

[0194] At block 1330, the fourth apparatus 140 receives data from a first apparatus on the configured grant based on the key of the fourth apparatus.

[0195] In some example embodiments, the method 1300 further comprising: in response to receiving the data on the configured grant, apply the key for a transmission with the first apparatus. The fourth apparatus 140 can thus apply the new key for following transmissions with the first apparatus.

[0196] In some example embodiments, the method 1300 further comprising: receiving an indication for activating the configured grant from at least one of: the second apparatus, or a third apparatus. Thus, the configured grant allocated by the fourth apparatus may be activated by the second apparatus and / or the third apparatus.

[0197] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0198] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0199] In some example embodiments, a first apparatus capable of performing any of the method 1100 (for example, the first apparatus 110 in FIG. 1) may comprise means for performing the respective operations of the method 1100. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1.

[0200] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus; means for performing a random access channel-less access to a third apparatus of the at least one candidate apparatus; and means for transmitting data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0201] In some example embodiments, the first apparatus may further comprise: means for in response to receiving a cell switch command indicating to switch to the third apparatus, generating the key of the fourth apparatus; and means for performing a RACH- less access to the fourth apparatus by transmitting the data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

[0202] In some example embodiments, the configuration is comprised in an RRC reconfiguration message.

[0203] In some example embodiments, the LTM configuration indicates that the configured grant is used for an inter-MN cell switch or an inter-CU cell switch.

[0204] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0205] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0206] In some example embodiments, another second apparatus capable of performing any of the method 1200 (for example, the second apparatus 120 in FIG. 1) may comprise means for performing the respective operations of the method 1200. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1.

[0207] In some example embodiments, the second apparatus comprises means for transmitting, to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; means for receiving, from the fourth apparatus, the configured grant; and means for transmitting, to a first apparatus, an LTM configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

[0208] In some example embodiments, the LTM configuration is comprised in an RRC reconfiguration message.

[0209] In some example embodiments, the second apparatus further comprises: means for transmitting an indication for activating the configured grant to at least one of the fourth apparatus, or a third apparatus of the at least one candidate apparatus.

[0210] In some example embodiments, the indication is included in at least one of a secondary node modification request to the fourth apparatus, or a cell switch notification of to the third apparatus.

[0211] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0212] In some example embodiments, another fourth apparatus capable of performing any of the method 1300 (for example, the fourth apparatus 140 in FIG. 1) may comprisemeans for performing the respective operations of the method 1300. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The fourth apparatus may be implemented as or included in the fourth apparatus 140 in FIG. 1.

[0213] In some example embodiments, the fourth apparatus may further comprise means for receiving, from a second apparatus, a request for a configured grant for a key of the fourth apparatus; means for transmitting, to the second apparatus, the configured grant; and means for receiving data from a first apparatus on the configured grant based on the key of the fourth apparatus.

[0214] In some example embodiments, the fourth apparatus may further comprise: means for in response to receiving the data on the configured grant, applying the key for a transmission with the first apparatus.

[0215] In some example embodiments, the fourth apparatus may further comprise: means for receiving an indication for activating the configured grant from at least one of: the second apparatus, or a third apparatus.

[0216] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0217] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0218] FIG. 14 shows a flowchart of another example method 1400 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1400 will be described from the perspective of the first apparatus 110 in FIG. 1.

[0219] At block 1410, the first apparatus 110 receives, from a second apparatus, a configuration for updating at least one data radio bearer (DRB) of a fourth apparatus, the configuration indicating a mapping between at least one logical channel and the at least one DRB.

[0220] At block 1420, the first apparatus 110 receives a cell switch command to switch to a third apparatus.

[0221] At block 1430, the first apparatus 110 generates the key of the fourth apparatus.

[0222] At block 1440, the first apparatus 110 updates the at least one DRB based on the configuration.

[0223] At block 1450, the first apparatus 110 transmits data to the fourth apparatus on the at least one updated DRB based on the key of the fourth apparatus.

[0224] In some example embodiments, the configuration is comprised in an LTM configuration indicating at least one candidate apparatus comprising the third apparatus. In some example embodiments, the configuration is comprised in an RRC reconfiguration message. In this manner, the RRC reconfiguration message such as the LTM configuration may indicate the DRB update configuration to be used in the inter-CU cell switch.

[0225] In some example embodiments, the configuration indicates a difference between a second DRB configuration and a first DRB configuration. The second DRB configuration may be used for an inter-MN LTM cell switch or an inter-CU LTM cell switch, and the first DRB configuration is applied before the cell switch. In this way, the difference or delta DRB configuration instead of the whole DRB configuration may be transmitted. The signaling overhead can thus be reduced.

[0226] In some example embodiments, the configuration comprises at least one identifier (ID) of the at least one DRB and at least one ID of at least one channel associated with the at least one DRB. The mapping between the new configured DRB(s) and the new logical channel(s) can be obtained.

[0227] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0228] FIG. 15 shows a flowchart of another example method 1500 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1500 will be described from the perspective of the second apparatus 120 in FIG. 1.

[0229] At block 1510, the second apparatus 120 transmits, to a fourth apparatus, a request for a configuration for updating at least one DRB of the fourth apparatus.

[0230] At block 1520, the second apparatus 120 receives, from the fourth apparatus, the configuration indicating a mapping between at least one logical channel and the at least one DRB.

[0231] At block 1530, the second apparatus 120 transmits the configuration to a first apparatus.

[0232] In some example embodiments, the configuration is comprised in an LTM configuration indicating at least one candidate apparatus. In some example embodiments, the configuration is comprised in an RRC reconfiguration message.

[0233] In some example embodiments, the configuration indicates a difference between a second DRB configuration and a first DRB configuration. The second DRB configuration is used for an inter-MN LTM cell switch or an inter-CU LTM cell switch, and the first DRB configuration is applied before the cell switch.

[0234] In some example embodiments, the configuration comprises at least one identifier of the at least one DRB and at least one ID of at least one channel associated with the at least one DRB.

[0235] In some example embodiments, the method 1500 further comprises: transmitting an indication for activating the at least one updated DRB to at least one of the fourth apparatus, or a third apparatus of at least one candidate apparatus. In this way, the updated DRB(s) can be optionally activated.

[0236] In some example embodiments, the indication is included in at least one of a secondary node modification request to the fourth apparatus, or a cell switch notification of to the third apparatus. Thus, the updated DRB(s) at the fourth apparatus can be optionally activated by the second apparatus and / or the third apparatus.

[0237] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0238] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0239] FIG. 16 shows a flowchart of another example method 1600 implemented at a fourth apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1600 will be described from the perspective of the fourth apparatus 140 in FIG. 1.

[0240] At block 1610, the fourth apparatus 140 receives, from a second apparatus, a request for a configuration for updating at least one DRB of the fourth apparatus.

[0241] At block 1620, the fourth apparatus 140 transmits, to the second apparatus, the configuration indicating a mapping between at least one logical channel and the at least one DRB.

[0242] At block 1630, the fourth apparatus 140 receives data from a first apparatus on the at least one updated DRB based on the key of the fourth apparatus.

[0243] In some example embodiments, the method 1600 further comprises: in response to receiving the data on the at least one updated DRB, applying the key for a transmission with the first apparatus on the at least one updated DRB. In this way, the fourth apparatus 140 may apply the updated DRB(s) for following transmissions with the first apparatus.

[0244] In some example embodiments, the configuration is comprised in an LTM configuration indicating at least one candidate apparatus. In some example embodiments, the configuration is comprised in an RRC reconfiguration message.

[0245] In some example embodiments, the configuration indicates a difference between a second DRB configuration and a first DRB configuration. The second DRB configuration is used for an inter-MN LTM cell switch or an inter-CU LTM cell switch, and the first DRB configuration is applied by the fourth apparatus before the cell switch.

[0246] In some example embodiments, the configuration comprises at least one identifier of the at least one DRB and at least one ID of at least one channel associated with the at least one DRB.

[0247] In some example embodiments, the method 1600 further comprises: receiving an indication for activating at least one updated DRB from at least one of: the second apparatus, or a third apparatus; and updating the at least one DRB based on the configuration. In this way, the updated DRB(s) at the fourth apparatus 140 may be activated by the indication from the second apparatus and / or the third apparatus.

[0248] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0249] In some example embodiments, another first apparatus capable of performing any of the method 1400 (for example, the first apparatus 110 in FIG. 1) may comprise means for performing the respective operations of the method 1400. The means may be implemented in any suitable form. For example, the means may be implemented in acircuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1.

[0250] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, a configuration for updating at least one DRB of a fourth apparatus, the configuration indicating a mapping between at least one logical channel and the at least one DRB; means for in response to receiving a cell switch command to switch to a third apparatus, generating the key of the fourth apparatus; means for updating the at least one DRB based on the configuration; and means for transmitting data to the fourth apparatus on the at least one updated DRB based on the key of the fourth apparatus.

[0251] In some example embodiments, the configuration is comprised in an LTM configuration indicating at least one candidate apparatus comprising the third apparatus.

[0252] In some example embodiments, the configuration is comprised in an RRC reconfiguration message.

[0253] In some example embodiments, the configuration indicates a difference between a second DRB configuration and a first DRB configuration, wherein the second DRB configuration is used for an inter-MN LTM cell switch or an inter-CU LTM cell switch, and the first DRB configuration is applied before the cell switch.

[0254] In some example embodiments, the configuration comprises at least one identifier (ID) of the at least one DRB and at least one ID of at least one channel associated with the at least one DRB.

[0255] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0256] In some example embodiments, another second apparatus capable of performing any of the method 1500 (for example, the second apparatus 120 in FIG. 1) may comprise means for performing the respective operations of the method 1500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1.

[0257] In some example embodiments, the second apparatus comprises means for transmitting, to a fourth apparatus, a request for a configuration for updating at least one data radio bearer (DRB) of the fourth apparatus; means for receiving, from the fourthapparatus, the configuration indicating a mapping between at least one logical channel and the at least one DRB; and means for transmitting the configuration to a first apparatus.

[0258] In some example embodiments, the configuration is comprised in an LTM configuration indicating at least one candidate apparatus.

[0259] In some example embodiments, the configuration is comprised in an RRC reconfiguration message.

[0260] In some example embodiments, the configuration indicates a difference between a second DRB configuration and a first DRB configuration. The second DRB configuration is used for an inter-MN LTM cell switch or an inter-CU LTM cell switch, and the first DRB configuration is applied before the cell switch.

[0261] In some example embodiments, the configuration comprises at least one identifier (ID) of the at least one DRB and at least one ID of at least one channel associated with the at least one DRB.

[0262] In some example embodiments, the second apparatus further comprises: means for transmitting an indication for activating the at least one updated DRB to at least one of the fourth apparatus, or a third apparatus of at least one candidate apparatus.

[0263] In some example embodiments, the indication is included in at least one of a secondary node modification request to the fourth apparatus, or a cell switch notification of to the third apparatus.

[0264] In some example embodiments, the cell switch comprises an inter-MN LTM cell switch or an inter-CU LTM cell switch.

[0265] In some example embodiments, another fourth apparatus capable of performing any of the method 1600 (for example, the fourth apparatus 140 in FIG. 1) may comprise means for performing the respective operations of the method 1600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The fourth apparatus may be implemented as or included in the fourth apparatus 140 in FIG. 1.

[0266] In some example embodiments, the fourth apparatus comprises means for receiving, from a second apparatus, a request for a configuration for updating at least one data radio bearer (DRB) of the fourth apparatus; means for transmitting, to the secondapparatus, the configuration indicating a mapping between at least one logical channel and the at least one DRB; and means for receiving data from a first apparatus on the at least one updated DRB based on the key of the fourth apparatus.

[0267] In some example embodiments, the fourth apparatus may further comprise: means for in response to receiving the data on the at least one updated DRB, applying the key for a transmission with the first apparatus on the at least one updated DRB.

[0268] In some example embodiments, the configuration is comprised in an LTM configuration indicating at least one candidate apparatus.

[0269] In some example embodiments, the configuration is comprised in an RRC reconfiguration message.

[0270] In some example embodiments, the configuration indicates a difference between a second DRB configuration and a first DRB configuration, wherein the second DRB configuration is used for an inter- MN LTM cell switch or an inter-CU LTM cell switch, and the first DRB configuration is applied by the fourth apparatus before the cell switch.

[0271] In some example embodiments, the configuration comprises at least one identifier (ID) of the at least one DRB and at least one ID of at least one channel associated with the at least one DRB.

[0272] In some example embodiments, the fourth apparatus may further comprise: means for receiving an indication for activating at least one updated DRB from at least one of: the second apparatus, or a third apparatus; and means for updating the at least one DRB based on the configuration.

[0273] In some example embodiments, the first apparatus is in a dual connectivity with the fourth apparatus.

[0274] FIG. 17 is a simplified block diagram of a device 1700 that is suitable for implementing example embodiments of the present disclosure. The device 1700 may be provided to implement a communication device, for example, the first apparatus 110, the second apparatus 120, the third apparatus 130 or the fourth apparatus 140 as shown in FIG. 1. As shown, the device 1700 includes one or more processors 1710, one or more memories 1720 coupled to the processor 1710, and one or more communication modules 1740 coupled to the processor 1710.

[0275] The communication module 1740 is for bidirectional communications. The communication module 1740 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 1740 may include at least one antenna.

[0276] The processor 1710 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1700 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.

[0277] The memory 1720 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 1724, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), an optical disk, a laser disk, and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random-access memory (RAM) 1722 and other volatile memories that will not last in the power-down duration.

[0278] A computer program 1730 includes computer executable instructions that are executed by the associated processor 1710. The instructions of the program 1730 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 1730 may be stored in the memory, e.g., the ROM 1724. The processor 1710 may perform any suitable actions and processing by loading the program 1730 into the RAM 1722.

[0279] The example embodiments of the present disclosure may be implemented by means of the program 1730 so that the device 1700 may perform any process of the disclosure as discussed with reference to FIG. 3 to FIG. 16. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0280] In some example embodiments, the program 1730 may be tangibly contained in acomputer readable medium which may be included in the device 1700 (such as in the memory 1720) or other storage devices that are accessible by the device 1700. The device 1700 may load the program 1730 from the computer readable medium to the RAM 1722 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0281] FIG. 18 shows an example of the computer readable medium 1800 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 1800 has the program 1730 stored thereon.

[0282] 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, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method 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.

[0283] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non- transitory computer readable medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. 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.

[0284] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code 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 code, 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.

[0285] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0286] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer 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 computer 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.

[0287] Further, although 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, although 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. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separatelyor in any suitable sub-combination.

[0288] Although the present disclosure has been described in languages 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

CLAIMS:

1. A first apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of the fourth apparatus; perform a random access channel (RACH)-less access to a third apparatus of the at least one candidate apparatus; and transmit data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

2. The first apparatus of claim 1, wherein the first apparatus is further caused to: in response to receiving a cell switch command indicating to switch to the third apparatus, generate the key of the fourth apparatus; and perform a RACH-less access to the fourth apparatus by transmitting the data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

3. The first apparatus of claim 1 or 2, wherein the configuration is comprised in a radio resource control (RRC) reconfiguration message.

4. The first apparatus of any of claims 1-3, wherein the LTM configuration indicates that the configured grant is used for an inter-master node (MN) cell switch or an intercentralized unit (CU) cell switch.

5. The first apparatus of any of claims 1-4, wherein the cell switch comprises an intermaster node (MN) LTM cell switch or an inter-centralized unit (CU) LTM cell switch.

6. The first apparatus of any of claims 1-5, wherein: the first apparatus comprises a terminal device, the second apparatus comprises one of the following: a next generation node B (gNB)47serving the first apparatus, a master node (MN) serving the first apparatus, or a centralized unit (CU) connecting with a distributed unit (DU) connecting with the first apparatus, the third apparatus comprises one of a further gNB, a further MN, a further DU, or a further CU connecting with a further DU, and the fourth apparatus comprises a secondary node, wherein the first apparatus is in a dual connectivity with the fourth apparatus.

7. A second apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; receive, from the fourth apparatus, the configured grant; and transmit, to a first apparatus, a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

8. The second apparatus of claim 7, wherein the LTM configuration is comprised in a radio resource control (RRC) reconfiguration message.

9. The second apparatus of claim 7 or 8, wherein the second apparatus is further caused to: transmit an indication for activating the configured grant to at least one of: the fourth apparatus, or a third apparatus of the at least one candidate apparatus.

10. The second apparatus of claim 9, wherein the indication is included in at least one of: a secondary node modification request to the fourth apparatus, or a cell switch notification of to the third apparatus.

11. The second apparatus of any of claims 7-10, wherein the cell switch comprises an inter- master node (MN) layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) cell switch or an inter-centralized unit (CU) LTM cell switch.

12. The second apparatus of any of claims 7-11, wherein: the first apparatus comprises a terminal device, the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a master node (MN) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU, the third apparatus comprises one of: a further gNB, a further MN, a further DU connecting with a further CU, or the further CU, and the fourth apparatus comprises a secondary node, wherein the first apparatus is in a dual connectivity with the fourth apparatus.

13. A fourth apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the fourth apparatus to: receive, from a second apparatus, a request for a configured grant for a key of the fourth apparatus; transmit, to the second apparatus, the configured grant; and receive data from a first apparatus on the configured grant based on the key of the fourth apparatus.

14. The fourth apparatus of claim 13, wherein the fourth apparatus is further caused to: in response to receiving the data on the configured grant, apply the key for a transmission with the first apparatus.

15. The fourth apparatus of claim 13 or 14, wherein the fourth apparatus is further caused to: receive an indication for activating the configured grant from at least one of: the second apparatus, or a third apparatus.

16. The fourth apparatus of any of claims 13-15, wherein the cell switch comprises an inter- master node (MN) layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) cell switch or an inter-centralized unit (CU) LTM cell switch.

17. The fourth apparatus of any of claims 13-16, wherein:the first apparatus comprises a terminal device, the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a master node (MN) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU, and the fourth apparatus comprises a secondary node, wherein the first apparatus is in a dual connectivity with the fourth apparatus.

18. A method comprising: receiving, at a first apparatus and from a second apparatus, a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus; performing a random access channel (RACH)-less access to a third apparatus of the at least one candidate apparatus; and transmitting data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

19. A method comprising: transmitting, from a second apparatus and to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; receiving, from the fourth apparatus, the configured grant; and transmitting, to a first apparatus, a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

20. A method comprising: receiving, at a fourth apparatus and from a second apparatus, a request for a configured grant for a key of the fourth apparatus; transmitting, to the second apparatus, the configured grant; and receiving data from a first apparatus on the configured grant based on the key of the fourth apparatus.

21. A first apparatus comprising: means for receiving, from a second apparatus, a layer 1 / layer 2 (L1 / L2) triggered50mobility (LTM) configuration, the LTM configuration indicating at least one candidate apparatus and a configured grant for a key of a fourth apparatus; means for performing a random access channel (RACH)-less access to a third apparatus of the at least one candidate apparatus; and means for transmitting data to the fourth apparatus on the configured grant based on the key of the fourth apparatus.

22. A second apparatus comprising: means for transmitting, to a fourth apparatus, a request for a configured grant for a key of the fourth apparatus; means for receiving, from the fourth apparatus, the configured grant; and means for transmitting, to a first apparatus, a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) configuration, the LTM configuration indicating at least one candidate apparatus and the configured grant for the key of the fourth apparatus.

23. A fourth apparatus comprising: means for receiving, from a second apparatus, a request for a configured grant for a key of the fourth apparatus; means for transmitting, to the second apparatus, the configured grant; and means for receiving data from a first apparatus on the configured grant based on the key of the fourth apparatus.

24. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of claim 18 or the method of claim 19 or the method of claim 20.

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