Configuration handover for lower layer triggered mobility

Abstract

Embodiments of the present disclosure relate to lower layer triggered mobility. In one aspect, a terminal device receives radio resource control signaling including a transmission configuration indicator from a first network device. The transmission configuration indicator state is configured to be used for beam-only switching, the terminal equipment executes the beam-only switching based on the transmission configuration indicator state and the first switching command, and then performs configuration switching based on the first switching command or the second switching command, so that a solution for enhancing lower layer trigger mobility is provided, and the user experience is improved. Therefore, the interruption time is reduced.

Description

Technical Field

[0001] Various example embodiments relate to the field of communications, and more particularly to a terminal device, a network device, a method, an apparatus, and a computer-readable storage medium for lower layer triggered mobility. Background Art

[0002] In the field of communications, continuous development is being carried out to provide efficient and reliable solutions for utilizing wireless communication networks. Each new generation of products has its own technical challenges, dealing with different situations and processes required to connect and serve wireless network devices. In order to meet the needs of the growing wireless data traffic since the deployment of the fourth generation (4G) communication system, people have been working on the development of improved fifth generation (5G) or quasi-5G communication systems. The new communication system can support multiple types of service applications for terminal devices.

[0003] Traditionally, the handover process is based on Layer 3 (L3) mobility, which may cause high latency. Lower Layer Triggered Mobility (LTM) is designed to improve mobility in order to further improve the robustness and interruption time of mobility. During the LTM process, mobility is triggered by Layer 2 (L2) based on Layer 1 (L1) measurements. However, the communication quality for LTM still needs to be improved. Summary of the invention

[0004] In general, example embodiments of the present disclosure provide a solution for enhanced lower layer triggered mobility.

[0005] In a first aspect, a terminal device is provided. The terminal device includes at least one processor and at least one memory storing instructions, and when the instructions are executed by the at least one processor, the terminal device performs at least the following operations: receiving radio resource control (RRC) signaling from a first network device, the RRC signaling including: (i) a transmission configuration indicator (TCI) state associated with a beam for a target cell provided by a second network device and (ii) a target cell configuration for a lower layer triggering handover LTM, wherein the TCI state is configured for beam-only handover; based on the TCI state and a first handover command from the second network device, performing a handover from a beam for a source cell provided by the second network device to a beam for a target cell; and based on the first handover command or a second handover command from the second network device, performing a second handover from the source cell configuration to the target cell configuration.

[0006] In a second aspect, a first network device is provided. The first network device includes at least one processor and at least one memory storing instructions, and when executed by the at least one processor, the instructions cause the network device to perform at least the following operations: transmitting a request for lower layer triggered handover (LTM) to a second network device, the request indicating an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; receiving a response for the LTM from the second network device, the response including: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only handover; and transmitting radio resource control (RRC) signaling including the TCI state and the target cell configuration to a terminal device.

[0007] In a third aspect, a second network device is provided. The second network device includes at least one processor and at least one memory storing instructions, and when executed by the at least one processor, the instructions cause the network device to perform at least the following operations: receiving a request for lower layer triggered handover (LTM) from a first network device, the request indicating an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; transmitting a response for the LTM to the first network device, the response including: (i) a transmission configuration indicator TCI state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only handover; and transmitting a first handover command for beam handover and a second handover command for configuring handover to a terminal device.

[0008] In a fourth aspect, a method is provided. The method includes receiving radio resource control (RRC) signaling from a first network device at a terminal device, the RRC signaling including: (i) a transmission configuration indicator (TCI) state associated with a beam for a target cell provided by a second network device and (ii) a target cell configuration for a lower layer triggering handover LTM, wherein the TCI state is configured for beam-only handover; based on the TCI state and a first handover command from the second network device, performing a first handover from a beam for a source cell provided by the second network device to a beam for a target cell; and based on the first handover command or the second handover command from the second network device, performing a second handover from the source cell configuration to the target cell configuration.

[0009] In a fifth aspect, a method is provided. The method comprises: transmitting, at a first network device and to a second network device, a request for a lower layer triggered handover (LTM), the request indicating an early beam handover for an LTM and a soft handover reference cell to a target cell provided by the second network device; receiving a response for the LTM from the second network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only handover; and transmitting to a terminal device a radio resource control (RRC) signaling including the TCI state and the target cell configuration.

[0010] In a sixth aspect, a method is provided. The method comprises: receiving, at a second network device, a request for lower layer triggered handover (LTM) from a first network device, the request indicating an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; transmitting to the first network device a response for the LTM, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only handover; and transmitting to a terminal device a first handover command for beam handover and a second handover command for configuring handover.

[0011] In a seventh aspect, an apparatus is provided. The apparatus comprises: a device for transmitting a request for lower layer triggered handover (LTM) at a first network device to a second network device, the request indicating an early beam handover for LTM and a soft handover reference cell to a target cell provided by the second network device; a device for receiving a response to LTM from the second network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam of the target cell and (ii) a target cell configuration for LTM, wherein the TCI state is configured for beam-only handover; and a device for transmitting radio resource control (RRC) signaling including the TCI state and the target cell configuration to a terminal device.

[0012] In an eighth aspect, an apparatus is provided. The apparatus comprises: a device for transmitting a request for lower layer triggered handover (LTM) at a first network device and to a second network device, the request indicating an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; a device for receiving a response to the LTM from the second network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only handover; and a device for transmitting radio resource control (RRC) signaling including the TCI state and the target cell configuration to a terminal device.

[0013] In a ninth aspect, a device is provided. The device includes: a device for receiving, at a second network device, a request for lower layer triggered handover (LTM) from a first network device, the request indicating an early beam handover for LTM and a soft handover reference cell to a target cell provided by the second network device; a device for transmitting a response for LTM to the first network device, the response including: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for LTM, wherein the TCI state is configured for beam-only handover; and a device for transmitting a first handover command for beam handover and a second handover command for configuring handover to a terminal device.

[0014] In a tenth aspect, a non-transitory computer-readable medium is provided, comprising program instructions for causing an apparatus to at least execute a method according to any one of the fourth, fifth and sixth aspects above.

[0015] In an eleventh aspect, a terminal device is provided. The terminal device includes a receiving circuit system configured to receive a radio resource control (RRC) signaling from a first network device, the RRC signaling including: (i) a transmission configuration indicator (TCI) state associated with a beam for a target cell provided by a second network device and (ii) a target cell configuration for a lower layer triggered handover (LTM), wherein the TCI state is configured for beam-only handover; an execution circuit system configured to perform a first handover from a beam for a source cell provided by the second network device to a beam for a target cell based on the TCI state and a first handover command from the second network device; and an execution circuit system configured to perform a second handover from the source cell configuration to the target cell configuration based on the first handover command or the second handover command from the second network device.

[0016] In a twelfth aspect, a first network device is provided. The first network device includes: a transmitting circuit system configured to transmit a request for a lower layer triggered handover (LTM) to a second network device, the request indicating an early beam switch for the LTM and a soft handover reference cell to a target cell provided by the second network device; a receiving circuit system configured to receive a response for the LTM from the second network device, the response including: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only switching; and a transmitting circuit system configured to transmit a radio resource control (RRC) signaling including the TCI state and the target cell configuration to a terminal device.

[0017] In a thirteenth aspect, a second network device is provided. The second network device includes a receiving circuit system configured to receive a request for a lower layer triggered handover (LTM) from a first network device, the request indicating an early beam handover for an LTM and a soft handover reference cell to a target cell provided by the second network device; a transmitting circuit system configured to transmit a response for the LTM to the first network device, the response including: (i) a transmission configuration indicator (TCI) state associated with a beam of the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only handover; and a transmitting circuit system configured to transmit a first handover command for beam handover and a second handover command for configuring handover to a terminal device.

[0018] In a fourteenth aspect, a computer program comprising instructions is provided, which, when executed by an apparatus, causes the apparatus to at least perform a method according to any one of the fourth, fifth and sixth aspects above.

[0019] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0021] Figure 1 shows an example communication network in which embodiments of the present disclosure may be implemented;

[0022] Figure 2 A flow chart illustrating a process for lower layer triggered mobility according to certain embodiments of the present disclosure;

[0023] Figure 3 A flow chart illustrating a process for lower layer triggered mobility according to some embodiments of the present disclosure;

[0024] Figure 4 A schematic diagram showing resource usage during LTM switching operations according to some embodiments of the present disclosure;

[0025] Figure 5 A schematic diagram showing resource usage at a target cell during a beam switching operation and after an LTM configuration switching operation according to some embodiments of the present disclosure;

[0026] Figure 6 A flowchart of a method implemented at a terminal device according to some embodiments of the present disclosure is shown;

[0027] Figure 7 A flowchart of a method implemented on a network device according to some embodiments of the present disclosure is shown;

[0028] Figure 8 A flow chart of a method implemented in another embodiment is shown. A network device according to some embodiments of the present disclosure;

[0029] Fig. 9 shows a simplified block diagram of a device suitable for implementing an embodiment of the present disclosure; and

[0030] Fig.10 A block diagram of an example computer-readable medium is shown in accordance with certain embodiments of the present disclosure.

[0031] Throughout the drawings, the same or similar reference numerals represent the same or similar elements. DETAILED DESCRIPTION

[0032] The principle of the present disclosure will now be described in conjunction with some example embodiments. It should be understood that these embodiments are only for illustrative purposes and are helpful for those skilled in the art to understand and implement the present disclosure, and are not intended to limit the scope of the present disclosure. The embodiments described herein can be implemented in various ways except for the way described below.

[0033] 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 skill in the art to which this disclosure belongs.

[0034] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the embodiment may include certain features, structures, or characteristics, but not every embodiment necessarily includes the certain features, structures, or characteristics. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a certain feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that those skilled in the art may affect such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0035] It should be understood that although the terms "first", "second", etc. in front of nouns 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 element and do not limit the order of the nouns. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the exemplary embodiments. The term "and / or" used herein includes any and all combinations of one or more of the listed terms.

[0036] The terms used herein are only used to describe specific embodiments and are not intended to limit exemplary embodiments. The singular forms "one", "an" and "the" used herein are also intended to include plural forms unless the context clearly states otherwise. It should be further understood that the terms "include", "include", "have", "have" and / or "include" and / or "include" used herein specify the presence of the features, elements and / or parts, etc., but do not exclude the presence or addition of one or more other features, elements, parts and / or their combinations. As used herein, "at least one of the following: <list of two or more elements>" and "at least one of <list of two or more elements>" and similar wording, wherein the list of two or more elements is connected by "and" or "or", indicating at least any one element, or at least any two or more elements, or at least all elements.

[0037] The term "circuitry" as used in this application may refer to one, more, or all of the following:

[0038] (a) hardware circuit implementation only (such as implementation only in analog and / or digital circuitry) and

[0039] (b) a combination of hardware circuitry and software such as (where applicable):

[0040] (i) a combination of analog and / or (multiple) digital hardware circuits and software / firmware, and

[0041] (ii) (multiple) hardware processors and software (including (multiple) digital signal processors), software and any portion of (multiple) memories, which work together to enable a device (such as a mobile phone or server) to perform various functions) and (c) (multiple) hardware circuits and / or (multiple) processors, such as (multiple) microprocessors or portions of (multiple) microprocessors, which (multiple) hardware circuits and / or (multiple) processors require software (e.g., firmware) to run, but the software may not be present when the software is not needed to run.

[0042] This definition of circuitry applies to all uses of the term in this application, including any claims. As a further example, as used in this application, the term "circuitry" also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. The term "circuitry" also covers, for example, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or network device, if applicable to a particular claim element.

[0043] The term "communication network" used herein refers to a network that complies with any appropriate communication standard, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal device and the network device in the communication network can be carried out according to any appropriate generation of communication protocols, including but not limited to the first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G), sixth generation (6G) communication protocols and / or any other currently known or future protocols to be developed. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communication, there will certainly be future types of communication technologies and systems that can embody the present disclosure. This should not be regarded as limiting the scope of the present disclosure to the above-mentioned systems.

[0044] As used herein, the term "network device" refers to a node in a communication network through which a terminal device accesses the network and receives services therefrom. Depending on the terminology and technology applied, a network device may refer to a base station (BS) or an access point (AP), for example, a NodeB (NodeB or NB), an evolved NodeB (eNodeB or eNB), a new radio (NR) next generation NodeB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, a low power node (e.g., a femto node, a micro node), etc. The RAN split architecture includes a gNB-CU (centralized unit, hosting RRC, SDAP, and PDCP) that controls multiple gNB-DUs (distributed units, hosting RLC, MAC, and PHY).

[0045] The term "terminal device" refers to any terminal device capable of wireless communication. As an example and not limitation, a terminal device may also be referred to as a communication device, a user equipment (UE), a user station (SS), a portable user station, a mobile station (MS), or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device (such as a digital camera), a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a notebook embedded device (LEE), a notebook mounted device (LME), a USB dongle, a smart device, a wireless client device (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain environments), consumer electronic devices, devices running on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0046] As mentioned above, LTM involves L1 measurements. The L1 measurement configuration of all candidate cells can be maintained as a common configuration, that is, outside the ServingCellConfig of the current serving cell and outside the configuration of the LTM candidate cells. The configuration of the TCI state of the candidate cell can be maintained as a common configuration, that is, outside the ServingCellConfig of the current serving cell and outside the configuration of the LTM candidate cells. For L1 measurements of LTM candidate cells, the reporting configuration can be placed in the ServingCellConfig of the current (multiple) serving cells. The target cell configuration is pre-configured through RRC signaling. Switching between prepared cells (also called dynamic switching) can be performed without reconfiguration. The dynamic switching mechanism between candidate serving cells is applicable to various potential scenarios, such as intra-distributed unit (DU) and inter-DU situations based on L1 / L2 signaling.

[0047] To enhance LTM, inter-cell beam management (ICBM) and LTM coexistence scenarios are considered, and LTM is triggered during ICBM. The UE will receive a MAC CE triggering a cell change command from a non-serving cell as it is more reliable than a borrowed beam. The MACCE is triggered by the serving cell DU, and the L1 measurement is relayed from the non-serving cell / DU to the serving cell DU to make an LTM decision during ICBM. If the UE is in ICBM, the CU will receive the L1 measurement and decide to trigger LTM from the serving cell to the non-serving cell. However, the configuration of ICBM and LTM is considered separate, and only the regular transition from ICBM to LTM is considered, i.e., how to trigger LTM if the UE is in ICBM. Any enhancements to the ICBM and LTM configurations to achieve a smooth transition from ICBM to LTM are not considered.

[0048] In addition, partial MAC resets are not supported, and the HARQ buffers are released. Pending MAC packets need to be retransmitted from higher layers (if supported). Otherwise, some interruptions will occur. For LTM and ICBM interworking, a separate RS configuration is provided for LTM measurements. This may also include intra-cell RS configuration for the current serving cell, because some current serving cells (e.g., secondary cells) may also be LTM candidate cells, or / and measurements from the current SpCell may be configured to be reported to compare quality with LTM candidate cells. If ICBM is also enabled for the same target cell, there will be redundant measurements and redundant resource configurations at the target cell, which need to be explicitly released through the RRC signaling process. TCI state switching for ICBM and LTM is triggered by different MAC CE commands.

[0049] Additionally, for intra-DU LTM handover scenarios, resetting the MAC level during handover should be avoided since the same scheduler is handling both cells. Independently configured LTM and ICBM for the same target cell is not signaled efficiently. Additionally, changes to the UE behavior are required to optimize L1 measurements for ICBM and LTM purposes. Managing these two measurement and reporting functions for the same target cell at the UE may result in capacity limitations.

[0050] Taking ICBM into consideration, the beam of the target cell can be indicated first, and then a cell switching command can be issued. Before issuing the cell switching command, the UE starts communicating with the target cell by using the indicated TCI state, and then sends a cell switching command to complete the switching process.

[0051] In this paper, ICBM enables beam measurements and the TCI state configuration of the serving cell can be extended by some beams for the target cell for intra-frequency and intra-DU scenarios. In order for ICBM to work seamlessly, the target cell needs to allocate resources for PDCCH and PUCCH at the same location of the serving cell to allow the UE to simply switch beam direction and continue to use the same resource configuration when inter-cell beam switching is triggered. PUCCH resource allocation for ICBM is required for regular PUCCH operation and is also required to continue L1 measurement reporting through the same PUCCH resources after inter-cell beam switching.

[0052] According to an embodiment of the present disclosure, a solution for delaying configuration switching for lower layer triggered mobility is provided. In this solution, a terminal device may receive a radio resource control (RRC) signaling containing a transmission configuration indicator (TCI) from a first network device, wherein the TCI state is configured for beam-only switching, and the terminal device may perform beam-only switching based on the TCI state and the first switching command, and then perform configuration switching based on the first switching command or the second switching command. In this way, a solution for enhancing lower layer triggered mobility is provided, thereby reducing the interruption time. The principles and embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0053] Figure 1 A schematic diagram of an example communication environment 100 in which some embodiments of the present disclosure may be implemented is shown. The environment 100 may be part of a communication network and include a base station. The base station may include a CU and one or more DUs. For ease of illustration and without limiting the present disclosure, Figure 1 A CU and a DU are shown in FIG. It should be noted that when the CU and the DU can be regarded as separate devices, the base station may include two devices, namely, a first network device corresponding to the CU and a second network device corresponding to the DU.

[0054] like Figure 1 As shown, environment 100 may include UE 110, CU 120, and DU 130. DU 130 is connected to CU 120. DU 130 may be partially controlled by CU 120. CU 120 may terminate an F1 interface connected to DU 130. DU 130 may terminate an F1 interface connected to CU 120. CU 120 may be a logical node hosting at least one of: Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP), and Packet Data Convergence Protocol (PDCP), protocols of a network device.

[0055] DU 130 may be a logical node that hosts at least one of the following: a radio link control (RLC), a medium access control (MAC), and a physical (PHY) layer of a network device. DU 130 may provide or support one or more cells. A cell is supported by only one DU. For example, DU 130 may provide cells 131 and 132. It should be understood that environment 100 may include any appropriate number of UEs, CUs, and DUs suitable for implementing implementations of the present disclosure.

[0056] Communications in environment 100 may follow any appropriate communication standards or protocols that already exist or will be developed in the future, such as Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Fifth Generation (5G) New Radio (NR), Wireless Fidelity (Wi-Fi), and Worldwide Interoperability for Microwave Access (WiMAX) standards, and employ any appropriate communication technology, including, for example, Multiple Input Multiple Output (MIMO), Orthogonal Frequency Division Multiplexing (OFDM), Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), Code Division Multiplexing (CDM), Bluetooth, ZigBee, and Machine Type Communication (MTC), Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), Ultra-Reliable Low Latency Communication (URLLC), Carrier Aggregation (CA), Dual Connectivity (DC), and New Radio Unlicensed (NR-U) technology.

[0057] UE 110 may access one cell provided by DU 130. For example, UE 110 may initially couple to cell 131 provided by DU 130. Based on the measurements, UE 110 may perform an intra-DU mobility procedure to move from cell 131 to cell 132 provided by DU 130.

[0058] Reference Figure 2 More details of some embodiments of the present disclosure are described. Figure 2 A signaling diagram of a process 200 for triggering mobility of lower layers according to various embodiments is shown. For discussion purposes only, reference will be made to Figure 1 The process 200 may involve UE 110 (corresponding to a terminal device), CU 120 (corresponding to a first network device), DU 130 (corresponding to a second network device), cell 131 (corresponding to a source cell), and Figure 1 It should be understood that any graphic elements, numerical values ​​and descriptive words in these figures are only for illustrative purposes and do not represent any limitation.

[0059] In process 200, CU 120 sends (202) a request for lower layer triggered handover (LTM) to DU 130. The request indicates an early beam switch for LTM and a soft handover reference cell to cell 132 provided by DU 130. In some embodiments, after receiving the request, DU 130 may reserve (204) soft handover resources for cell 132 at the same location as the soft handover reference cell (e.g., cell 131).

[0060] On the second first device side, in response to the request, DU 130 transmits (206) a response to the LTM to CU 120. The response includes: (i) a transmission configuration indicator (TCI) state associated with the beam for cell 132 and (ii) a target cell configuration for the LTM. The TCI state is configured for beam switching only. On the other side of the communication, CU 120 receives the response to the LTM from DU 130 and transmits (208) a radio resource control (RRC) signaling to UE 110. The RRC signaling includes the TCI state and the target cell configuration.

[0061] On the terminal device side, UE 110 receives RRC signaling. In some embodiments, the RRC signaling also includes a reference signal (RS) configuration associated with a beam for cell 132. Upon receiving the RRC signaling, UE 110 may transmit (210) to DU 130 a layer 1 (L1) measurement report generated based on the RS configuration.

[0062] On the other side of the communication, after receiving the L1 measurement report, DU 130 transmits (212) a first handover command for beam switching to UE 110. In some embodiments, in the case where cell 132 is in an LTM cell group for soft handover, DU 130 may transmit the first handover command based on the L1 measurement report. Information of the LTM cell group may be included in RRC signaling.

[0063] On the terminal device side, after receiving the first switching command, UE 110 performs (214) a first switching from a beam for cell 131 provided by DU 130 to a beam for cell 132 based on the TCI state and the first switching command. The first switching command may include the TCI state. Next, UE 110 may transmit a beam switching message to DU 130.

[0064] In some embodiments, after performing the first switching, UE 110 may use the soft switching resources associated with the beam-only switching for LTM to perform transmission to or reception from DU 130. Meanwhile, after receiving the beam switching message, DU 130 may use the soft switching resources to perform transmission to or reception from UE 110.

[0065] On the second first device side, DU 130 transmits (216) a second handover command for configuring the handover to UE 110. On the other side of the communication, based on the first handover command or the second handover command from DU 130, UE 110 performs (218) a second handover from the source cell configuration to the target cell configuration. The second handover command may be an LTM handover command without a TCI state. Upon receiving the LTM handover command without a TCI state, UE 110 may perform transmission to or reception from DU 130 using target cell resources associated with the target cell configuration.

[0066] In some embodiments, the first handover command may include a flag indicating a delayed configuration handover and a delay value (e.g., an expiration value of a timer). Next, as described above, UE 110 performs the first handover. In one example, UE 110 also performs a second handover based on the expiration of the timer. In another example, UE 110 also receives a second handover command transmitted by DU 130 based on the completion of transmission or reception through the soft handover resource, and performs the second handover.

[0067] In some embodiments, before receiving the second handover command, UE 110 may also receive a timer extension command from DU 130 to delay the second handover. Alternatively, before receiving the second handover command, UE 110 may also receive a handover rejection command from DU 130 to cancel the second handover. In addition, after performing the second handover, UE 110 may also transmit an LTM completion message to DU 130 and release soft handover resources.

[0068] Now refer to Figure 1 Some embodiments of the present disclosure are further described in detail. 3 For a clearer understanding, please see below. Figure 3 An example of a process 300 for lower layer triggered mobility according to some example embodiments of the present disclosure is shown.

[0069] exist Figure 3 In, an enhanced procedure is proposed for preparing an intra-DU LTM target cell for beam-only switching operation before configuration switching. The procedure implements a single preparation procedure for combined beam switching and LTM configuration switching to the same cell. When the target cell supports such operation, i.e., initially beam-only switching followed by LTM configuration switching (i.e., cell switching), the source / serving DU can flexibly delay the configuration switching based on the pending data transmission of Layer 1 (or based on the interruption time requirement). Since the pending data packets are transmitted through the beam switching operation without the need for a MAC reset, the interruption time due to the loss of lower layer data packets can be minimized for the intra-DU LTM target cell.

[0070] More specifically, the UE may establish an RRC connection with cell 1 at the source DU and send (301) a measurement report to the CU. When preparing the target cell for LTM, the CU may indicate "beam switching only supported" to the target DU. The CU also includes the serving cell L1 report configuration. In other words, when preparing the target cell within the DU for LTM switching, the CU will request early beam switching in the preparation message. Figure 3 As shown, the CU sends (302) a UE environment setup request to the DU providing the target cell. The request indicates an early beam switch from the reference cell to the target cell for LTM and soft handover.

[0071] Based on this request, in blocks 303 and 304, in addition to preparing the target resources for LTM purposes, the target cell also reserves or copies resources (PUCCH / PDCCH / L1 reporting resources) for soft handover (beam-only handover) at the same location as the reference cell (which can be the current serving cell by default) to allow beam handover to work. These resources are called "soft handover" resources and are used for seamless beam-only handover. Soft handover resources will be described in the following Figure 4 Further explanation in.

[0072] If resource reservation for beam-only switching is possible, the DU may inform the CU in a response message that beam-only switching is activated and provide the LTM-RS configuration and target configuration to be used for switching. Figure 3 As shown, the DU sends (305) a UE environment setup response to the CU. The response may include only a beam switching enable indication, an LTM RS configuration, an LTM TCI configuration, and a target RRC reconfiguration.

[0073] After the above preparation process, the RRC configuration process may be performed. Specifically, after receiving the response from the DU, the CU may send (306) an RRC reconfiguration message to the UE. The RRC reconfiguration message includes the TCI state that can perform beam-only switching. For example, Figure 3 As shown, the RRC reconfiguration message includes LTM RS configuration, LTM TCI configuration, LTM target configuration and LTM cell group for soft switching. LTM RS configuration and LTM TCI state configuration are configured as common configurations. Some target cells or / and TCI states are marked as beam switching only. This means that the TCI states of these target cells can be used for beam switching only. When these TCI states are indicated separately, the UE can trigger beam switching. When other TCI states are indicated, the UE can only start downlink synchronization to those target cells without switching PUCCH / PDCCH resources.

[0074] In one example, the RRC reconfiguration message indicates a candidate cell for which beam-only switching can be performed. When the TCI state associated with such a candidate cell is indicated, the UE may first trigger beam switching only for that candidate cell.

[0075] After receiving the RRC reconfiguration message, the UE may send (307) a LI measurement report to the DU. At block 308, the DU may decide to trigger a beam-only handover if the target cell belongs to the same group as the soft handover. At block 309, the DU may decide to trigger a beam handover first based on the pending MAC data packet and the target cell.

[0076] Next, there are two options for the subsequent LTM switching execution process. In option 1, the DU can send (310) a TCI switching command to the UE indicating the target beam of the prepared LTM cell. In response to the TCI switching command, the UE can perform a beam-only switching. The beam switching message can be transmitted (312) from the UE to the target cell of the DU. At box 314, the UE can use soft switching resources for PUCCH / PDCCH / L1 reporting. After performing beam-only switching, the UE can receive (316) an LTM switching command without TCI status from the target cell of the DU. In response to the LTM switching command, the UE can apply the target cell configuration at box 318. In addition, the UE can use the target cell resources for PUCCH / PDCCH / L1 reporting at box 320.

[0077] Additional procedures for maintaining soft handover resources may be included in example embodiments of the present disclosure. If the target cell wants to remove soft handover resources due to resource limitations, the DU should disable soft handover for these target cells. This can be indicated by Layer 2 (MAC-CE command) or Layer 1 (DCI) to disable soft handover for a specific set of target cells. In one example, an LTM completion may be transmitted (322) from the UE to the target cell of the DU. The UE may release (324) the soft handover resources. Accordingly, the DU may release (326) the soft handover resources of the target cell.

[0078] Alternatively, a common TCI state pool for LTM is used, including TCI states for beam-only switching or both beam and configuration switching. When the TCI state indication from the pool is for beam-only switching, an explicit flag of "beam-only switching" can be given together with the TCI state indication. For example, in option 2, the DU can send (328) an LTM switching command to the UE, and the LTM switching command can include the target cell ID, the TCI state, and a flag indicating delayed configuration switching. The flag indicates that the UE should switch beams first and after a fixed delay. This delay can be explicitly included in the switching command.

[0079] In response to the LTM handover command with TCI state, the UE may switch beams and use soft handover resources for communication at block 330. On the DU side, at block 332, if the last packet transmission is complete, the DU may trigger the handover via a single bit indication in the MAC / PDCCH. Next, the handover indication may be transmitted (334) from the DU to the UE via the PDCCH / MAC.

[0080] Alternatively, the DU (or target cell) may trigger LTM switching via a single bit indication in PDCCH or MAC when a pending transmission is completed before the timer expires, rather than indicating a delay value (eg, timer expiration value) in the LTM switching command.

[0081] On the UE side, at block 336, the UE applies (336) the target cell configuration by timer expiration and receipt of a handover indication. The UE may release (324) the soft handover resources. Thus, the DU may release (326) the soft handover resources for the target cell.

[0082] For further explanation, more details are given below. In option 1, based on the pending packets at the MAC level at the time of switching, the DU may decide to send a TCI switching command (also referred to as the first switching command here) including the TCI state associated with the beam for the target cell for beam switching. Subsequently, an LTM switching command (also referred to as the second switching command here) without beam indication and TCI state is provided for LTM configuration switching.

[0083] Since the soft switching resources (or PUCCH / PDCCH / LI reporting resources) for beam switching operation have been configured during the preparation process to enable dynamic activation, when the DU decides to perform beam-only switching, the DU can activate the soft switching resources before the beam-only switching.

[0084] In option 2, based on the pending packets at the MAC level at the time of handover, the LTM handover command with TCI state (here also considered as the first handover command) includes an additional flag for delayed configuration handover with a delay value (e.g., timer expiration value). Such operation can only be enabled for candidate cells (or TCI states) indicating "beam only handover support". In this case, the UE first switches only the beam, then applies the target cell configuration and triggers LTM completion after the configured delay.

[0085] In addition, after sending the LTM handover command (or the first handover command) with the flag and delay timer value for delayed configuration handover, a timer extension command (via DCI or MAC-CE) can be sent to extend the configuration handover delay. In addition, after sending the LTM handover command with the flag and delay timer value for delayed configuration handover, a handover rejection command (via DCI or MAC-CE) can be sent to cancel the LTM handover. In this case, the UE will continue in beam switching mode.

[0086] Figure 4 A schematic diagram showing resource usage during LTM switching operation is shown. Figure 5 FIG. 2 shows a schematic diagram of resource usage at the target cell during beam switching operation and after LTM configuration switching operation. Figure 4 and Figure 5 In FIG. 4 , two resource locations allocated for soft handover operation are given for the target cell. One of the resource locations (corresponding to the soft handover resources 410 for beam-only handover) can be used for beam handover operation, while the other resource location (corresponding to the target cell resources 420, i.e., the resources after LTM configuration handover) can be used for new serving cell (i.e., target cell) operation. The soft handover resources 410 can be co-located with the source cell resources 430 of the serving cell.

[0087] Figure 6 FIG. 6 is a flow chart showing an example method 600 implemented at a terminal device according to some embodiments of the present disclosure. For the purpose of discussion, reference will be made to the method 600 from the perspective of the UE 110. Figure 1 Method 600 is described.

[0088] At block 610, UE 110 receives radio resource control (RRC) signaling from a first network device, the signaling including: (i) a transmission configuration indicator (TCI) state associated with a beam for a target cell provided by a second network device and (ii) a target cell configuration for a lower layer triggered handover (LTM), wherein the TCI state is configured for beam-only handover. At block 620, UE 110 performs a first handover from a beam for a source cell provided by the second network device to a beam for a target cell based on the TCI state and a first handover command from the second network device. At block 630, UE 110 performs a second handover from the source cell configuration to the target cell configuration based on the first handover command or the second handover command from the second network device.

[0089] In some embodiments, after performing the first handover, UE 110 also performs transmission to or reception from the second network device using soft handover resources associated with beam-only handover for LTM.

[0090] In some embodiments, the RRC signaling also includes a reference signal (RS) configuration associated with the beam for the target cell. After receiving the RRC signaling, UE 110 also transmits a layer 1 (L1) measurement report generated based on the RS configuration to the second network device.

[0091] In some embodiments, the RRC signaling further includes information of an LTM cell group for soft handover, and when the target cell is located in the LTM cell group, the second network device transmits a first handover command based on the L1 measurement report.

[0092] In some embodiments, the second handover command is an LTM handover command without a TCI state. After receiving the LTM handover command without a TCI state, UE 110 further performs transmission to and reception from the second network device using target cell resources associated with the target cell configuration.

[0093] In some embodiments, the first switching command includes a flag indicating a delay configuration switch and a delay value.

[0094] In some embodiments, the second switching is performed based on expiration of the delay value.

[0095] In some embodiments, before receiving the second handover command, UE 110 further receives a timer extension command for delaying the second handover from the second network device.

[0096] In some embodiments, the second handover command is transmitted by the second network device based on completion of the transmission or reception via the soft handover resource.

[0097] In some embodiments, before receiving the second handover command, UE 110 further receives a handover reject command for canceling the second handover from the second network device.

[0098] In some embodiments, after performing the second handover, UE 110 further transmits an LTM completion message to the second network device and releases the soft handover resources.

[0099] In some embodiments, the first network device is a central unit of a base station, and the second network device is a distributed unit of the base station.

[0100] Figure 7 FIG. 7 is a flowchart of an example method 700 implemented at a second network device according to some embodiments of the present disclosure. For the purpose of discussion, reference will be made to Figure 1 The method 700 is described from the perspective of the DU 130 .

[0101] At block 710, DU 130 receives a request for lower layer triggered handover (LTM) from a first network device, the request indicating an early beam handover for an LTM and soft handover reference cell to a target cell provided by a second network device. At block 720, DU 130 transmits a response for the LTM to the first network device, the response including: (i) a transmission configuration indicator (TCI) state associated with a beam of the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only handover. At block 730, DU 130 transmits a first handover command for beam handover and a second handover command for configuring handover to the terminal device.

[0102] In some embodiments, DU 130 also reserves soft handover resources for the target cell at the same location as the soft handover reference cell, and upon receiving the beam handover message, DU 130 also performs transmission to or reception from the terminal device using the soft handover resources associated with the beam-only handover for LTM.

[0103] In some embodiments, the response also includes a reference signal (RS) configuration associated with the beam for the target cell.DU 130 also receives from the terminal device a layer 1 (L1) measurement report generated by the terminal device based on the RS configuration transmitted from the first network device.

[0104] In some embodiments, in the case where the target cell is located in the LTM cell group for soft handover, the second network device transmits the first handover command based on the L1 measurement report.

[0105] In some embodiments, the second handover command is an LTM handover command without a TCI state. After transmitting the LTM handover command without a TCI state, DU 130 further utilizes the target cell resources associated with the target cell configuration to perform transmission to or reception from the terminal device.

[0106] In some embodiments, the first switching command includes a flag indicating a delay configuration switch and a delay value.

[0107] In some embodiments, configuration switching is performed based on expiration of a delay value.

[0108] In some embodiments, after transmitting the first switching command, the DU 130 further transmits a timer extension command for delaying the second switching to the terminal device.

[0109] In some embodiments, the second handover command is transmitted by the second network device based on completion of the transmission or reception via the soft handover resource.

[0110] In some embodiments, after transmitting the first handover command, the DU 130 further transmits a handover reject command for canceling the second handover to the terminal device.

[0111] In some embodiments, DU 130 also receives an LTM completion message from the terminal device and releases the soft handoff resources.

[0112] In some embodiments, the first network device is a central unit of a base station. The second network device is a distributed unit of the base station.

[0113] Figure 8 FIG. 8 is a flow chart showing an example method 800 implemented at a first network device according to some embodiments of the present disclosure. For the purpose of discussion, reference will be made to Figure 1 The method 800 is described from the perspective of the CU 120 .

[0114] In block 810, CU 120 transmits a request for lower layer triggered handover (LTM) to a second network device, the request indicating an early beam handover for LTM and a soft handover reference cell to a target cell provided by the second network device. In block 820, CU 120 receives a response for LTM from the second network device, the response including: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for LTM, wherein the TCI state is configured for beam-only handover. In block 830, CU 120 transmits a radio resource control (RRC) signaling including the TCI state and the target cell configuration to the terminal device.

[0115] In some embodiments, the first network device is a central unit of a base station. The second network device is a distributed unit of the base station.

[0116] In some embodiments, a device capable of performing method 600 (e.g., UE 110) may include a device for performing each step of method 600. These devices may be implemented in any suitable form. For example, these devices may be implemented in the form of a circuit system or a software module.

[0117] In some embodiments, the apparatus includes: an apparatus for receiving radio resource control (RRC) signaling from a first network device at a terminal device, the RRC signaling including: (i) a transmission configuration indicator (TCI) state associated with a beam for a target cell provided by a second network device and (ii) a target cell configuration for lower layer triggered switching (LTM), wherein the TCI state is configured for beam-only switching; an apparatus for performing a first switching from a beam for a source cell provided by the second network device to a beam for a target cell based on the TCI state and a first switching command from the second network device; and an apparatus for performing a second switching from the source cell configuration to the target cell configuration based on the first switching command or the second switching command from the second network device.

[0118] In some embodiments, the apparatus further comprises means for performing transmission to or reception from the second network device using soft handoff resources associated with the beam-only handoff for LTM after performing the first handoff.

[0119] In some embodiments, the RRC signaling also includes a reference signal (RS) configuration associated with a beam for the target cell, and the apparatus further includes a device for transmitting a layer 1 (L1) measurement report generated based on the RS configuration to a second network device after receiving the RRC signaling.

[0120] In some embodiments, the RRC signaling further includes information of an LTM cell group for soft handover, and when the target cell is located in the LTM cell group, the second network device transmits the first handover command based on the L1 measurement report.

[0121] In some embodiments, the second switching command is an LTM switching command without a TCI state, and the device also includes: after receiving the LTM switching command without a TCI state, a device is used to perform transmission to or reception from the second network device using target cell resources associated with the target cell configuration.

[0122] In some embodiments, the first switching command includes a flag indicating a delay configuration switch and a delay value.

[0123] In some embodiments, the second switching is performed based on expiration of the delay value.

[0124] In some embodiments, the apparatus further comprises means for receiving a timer extension command for delaying the second handover from the second network device before receiving the second handover command.

[0125] In some embodiments, the second handover command is transmitted by the second network device based on completion of the transmission or reception via the soft handover resource.

[0126] In some embodiments, the apparatus further comprises means for receiving a handover reject command for cancelling the second handover from the second network device before receiving the second handover command.

[0127] In some embodiments, the apparatus further comprises means for transmitting an LTM completion message to the second network device and for releasing soft handoff resources after performing the second handoff.

[0128] In some embodiments, the first network device is a central unit of a base station, and the second network device is a distributed unit of the base station.

[0129] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 600. In some embodiments, the apparatus comprises at least one processor and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the apparatus to perform.

[0130] In some embodiments, a device capable of performing method 700 (eg, DU 130) may include a device for performing the corresponding steps of method 700. The device may be implemented in any suitable form. For example, the device may be implemented in a circuit system or a software module.

[0131] In some embodiments, the apparatus includes an apparatus for receiving a lower layer triggered handover (LTM) request at a second network device and from a first network device, the request indicating an early beam switch for an LTM and a soft handover reference cell to a target cell provided by the second network device; an apparatus for transmitting a response for the LTM to the first network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only switching; and an apparatus for transmitting a first handover command for beam switching and a second handover command for configuring the switch to a terminal device.

[0132] In some embodiments, the apparatus further comprises: an apparatus for reserving soft switching resources for a target cell at the same location as a soft switching reference cell; and an apparatus for performing transmission to or reception from a terminal device using soft switching resources associated with beam-only switching of the LTM after receiving a beam switching message.

[0133] In some embodiments, the response also includes a reference signal (RS) configuration associated with the beam for the target cell.The apparatus also includes means for receiving from the terminal device a layer 1 (L1) measurement report generated by the terminal device based on the RS configuration transmitted from the first network device.

[0134] In some embodiments, in a case where the target cell is located in the LTM cell group for soft handover, the second network device transmits the first handover command based on the L1 measurement report.

[0135] In some embodiments, the second handover command is an LTM handover command without TCI status.The apparatus further comprises: after transmitting the LTM handover command without TCI status, means for performing transmission to or reception from the terminal device using target cell resources associated with the target cell configuration.

[0136] In some embodiments, the first switching command includes a flag indicating a delay configuration switch and a delay value.

[0137] In some embodiments, configuration switching is performed based on expiration of a delay value.

[0138] In some embodiments, the apparatus further comprises means for transmitting, to the terminal device, a timer extension command for delaying the second switching after transmitting the first switching command.

[0139] In some embodiments, the second handover command is transmitted by the second network device based on completion of the transmission or reception via the soft handover resource.

[0140] In some embodiments, the apparatus further comprises means for transmitting, to the terminal device, a handover rejection command for cancelling the second handover after transmitting the first handover command.

[0141] In some embodiments, the apparatus further comprises means for receiving an LTM completion message from a terminal device; and means for releasing soft handoff resources.

[0142] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 700. In some embodiments, the apparatus comprises at least one processor and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause execution of the apparatus.

[0143] In some embodiments, a device capable of executing method 800 (eg, CU 120) may include a device for executing the corresponding steps of method 800. The device may be implemented in any suitable form. For example, the device may be implemented in a circuit system or a software module.

[0144] In some embodiments, the apparatus includes: an apparatus for transmitting a lower layer triggered handover (LTM) request on a first network device and to a second network device, the request indicating an early beam switch for an LTM and a soft handover reference cell to a target cell provided by the second network device; an apparatus for receiving a response to the LTM from the second network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only switching; and an apparatus for transmitting radio resource control (RRC) signaling including the TCI state and the target cell configuration to a terminal device.

[0145] In some embodiments, the first network device is a central unit of a base station, and the second network device is a distributed unit of the base station.

[0146] In some embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 800. In some embodiments, the apparatus comprises at least one processor and at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processor, cause execution of the apparatus.

[0147] Fig. 9 is a simplified block diagram of a device 900 suitable for implementing an embodiment of the present disclosure. The device 900 may be provided to implement a communication device, such as Figure 1 The UE 110, CU 120 or DU 130 are shown. As shown, the device 900 includes one or more processors 910, one or more memories 920 coupled to the processors 910, and one or more communication modules 940 coupled to the processors 910.

[0148] The communication module 940 is used for two-way communication. The communication module 940 has at least one antenna to facilitate communication. The communication interface may represent any interface required to communicate with other network elements.

[0149] Processor 910 may be of any type suitable for the local technology network, and may include one or more of the following: a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture (as non-limiting examples). Device 900 may have multiple processors, such as application specific integrated circuit chips, which are time-slaved to a clock synchronized with a main processor.

[0150] The memory 920 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 924, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic and / or optical memories. Examples of volatile memories include, but are not limited to, random access memory (RAM) 922 and other volatile memories that do not persist during power outages.

[0151] The computer program 930 includes computer executable instructions that are executed by the associated processor 910. The program 930 may be stored in the ROM 1020. The processor 910 may perform any appropriate actions and processes by loading the program 930 into the RAM 922.

[0152] The embodiments of the present disclosure may be implemented by a program 930, so that the device 900 may execute the Figures 2 to 5 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0153] In some embodiments, the program 930 may be tangibly embodied in a computer-readable medium, which may be included in the device 900 (such as in the memory 920) or in other storage devices accessible to the device 900. The device 900 may load the program 930 from the computer-readable medium to the RAM 922 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. Fig.10 One example of a computer readable medium 1000 is shown in the form of a CD or DVD. The computer readable medium has a program 930 stored thereon.

[0154] In general, various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are shown and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that the boxes, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general hardware, or controllers or other computing devices, or some combination thereof, as non-limiting examples.

[0155] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer executable instructions, such as instructions included in program modules, which are executed in a device on a target real or virtual processor to perform the above referenced Figures 2 to 5 The method described. Typically, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The functions of program modules can be combined or split between program modules as required by various embodiments. The machine executable instructions of program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0156] The program code for executing the disclosed method can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the processor or controller executes the program code, the program code causes the function / operation specified in the flow chart and / or block diagram to be realized. The program code can be executed entirely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or completely on a remote machine or server.

[0157] In the context of the present disclosure, computer program codes or related data may be carried by any appropriate carrier to enable a device, apparatus or processor to perform the above-mentioned various processes and operations. Examples of carriers include signals, computer-readable media, etc.

[0158] The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or apparatuses, or any suitable combination of the above. More specific examples of computer-readable storage media include an electrical connection with one or more wires, a portable computer disk, 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 disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. The term "non-transient" as used herein is a limitation on the medium itself (i.e., tangible, not a signal), not a limitation on the persistence of data storage (e.g., RAM vs. ROM).

[0159] In addition, although the operations are shown in a specific order, it should not be understood that these operations are required to be performed in the specific order shown or in a continuous order, or that all the operations shown are required to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although the above discussion contains several specific implementation details, they should not be interpreted as limitations on the scope of the present disclosure, but rather as descriptions of the features of specific embodiments. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable sub-combination.

[0160] Although the present disclosure has been described using language specific to structural features and / or methodological actions, it should be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or actions described above. Instead, the specific features and actions described above are disclosed as example forms of implementing the claims.

Claims

1. A terminal device, comprising: at least one processor; as well as at least one memory storing instructions, when the instructions are executed by the at least one processor, causing the terminal device to at least perform the following operations: receiving radio resource control (RRC) signaling from a first network device, the radio resource control (RRC) signaling comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for a target cell provided by a second network device, and (ii) a target cell configuration for a lower layer triggered handover (LTM), wherein the TCI state is configured for beam-only handover; Based on the TCI state and a first handover command from the second network device, performing a first handover from the beam for the source cell provided by the second network device to the beam for the target cell; as well as Based on the first handover command or the second handover command from the second network device, a second handover from the source cell configuration to the target cell configuration is performed.

2. The terminal device according to claim 1, wherein the terminal device is further configured to perform the following operations: After performing the first handover, transmission to or reception from the second network device is performed using soft handover resources associated with the beam-only handover for the LTM.

3. The terminal device according to claim 1 or 2, wherein the RRC signaling further comprises: a reference signal (RS) configuration associated with the beam for the target cell, and the terminal device is further caused to perform the following operations: After receiving the RRC signaling, a layer 1 L1 measurement report generated based on the RS configuration is transmitted to the second network device.

4. The terminal device according to claim 3, wherein the RRC signaling further includes information for soft switching of an LTM cell group, and when the target cell is located within the LTM cell group, the first switching command is transmitted by the second network device based on the L1 measurement report.

5. The terminal device according to any one of claims 1 to 4, wherein the second switching command is an LTM switching command without a TCI state, and the terminal device is further configured to perform the following operations: After receiving the LTM handover command without the TCI state, performing transmission to or reception from the second network device using target cell resources associated with the target cell configuration.

6. The terminal device according to any one of claims 1 to 4, wherein the first switching command comprises: A flag indicating a delay configuration switch, and a delay value. 7 . The terminal device according to claim 6 , wherein the second switching is performed based on expiration of the delay value.

8. The terminal device according to claim 6 or 7, wherein the terminal device is further configured to perform the following operations: Before receiving the second switching command, a timer extension command for delaying the second switching is received from the second network device.

9. The terminal device according to claim 6, wherein the second handover command is transmitted by the second network device based on completion of the transmission or the reception via a soft handover resource.

10. The terminal device according to any one of claims 1 to 9, wherein the terminal device is further configured to perform the following operations: Before receiving the second handover command, a handover reject command for canceling the second handover is received from the second network device.

11. The terminal device according to any one of claims 1 to 10, wherein the terminal device is further configured to perform the following operations: After performing the second switching, transmitting an LTM completion message to the second network device; and The soft switching resources are released.

12. The terminal device according to any one of claims 1 to 10, wherein: The first network device is a central unit of a base station; and The second network device is a distributed unit of a base station.

13. A second network device, comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by at least one processor, causes the second network device to at least perform the following operations: receiving a request for a lower layer triggered handover LTM from a first network device, the request indicating: an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; transmitting a response to the LTM to the first network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell, and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only switching; as well as A first switching command for beam switching and a second switching command for configuration switching are sent to the terminal device.

14. The second network device according to claim 13, wherein the second network device is further configured to perform the following operations: For the target cell, reserving soft handover resources at the same location as the soft handover reference cell; and After receiving a beam switching message, transmission to or reception from the terminal device is performed using the soft handover resources associated with the beam-only switch for the LTM.

15. The second network device according to claim 13 or 14, wherein the response further comprises: A reference signal (RS) configuration associated with the beam for the target cell, and the second network device is further configured to perform the following operations: A layer 1 L1 measurement report generated by the terminal device based on the RS configuration transmitted from the first network device is received from the terminal device. 16 . The second network device according to claim 15 , wherein in a case where the target cell is located in an LTM cell group for soft handover, the first handover command is transmitted by the second network device based on the L1 measurement report.

17. The second network device according to any one of claims 13 to 16, wherein the second switching command is an LTM switching command without the TCI state, and the second network device is further configured to perform the following operations: After transmitting the LTM handover command without the TCI state, performing transmission to or reception from the terminal device using target cell resources associated with the target cell configuration.

18. The second network device according to any one of claims 13 to 16, wherein the first switching command comprises: A flag indicating a delay configuration switch, and a delay value.

19. The second network device of claim 18, wherein the configuration switching is performed based on expiration of the delay value.

20. The second network device according to claim 18 or 19, wherein the second network device is further configured to perform the following operations: After the first switching command is transmitted, a timer extension command for delaying the second switching is transmitted to the terminal device.

21. The second network device of claim 18, wherein the second handover command is transmitted by the second network device based on completion of the transmission or the reception via the soft handover resource.

22. The second network device according to any one of claims 13 to 21, wherein the second network device is further configured to perform the following operations: After the first switching command is transmitted, a switching rejection command for canceling the second switching is transmitted to the terminal device.

23. The second network device according to any one of claims 13 to 22, wherein the second network device is further configured to perform the following operations: receiving an LTM completion message from the terminal device; and The soft switching resources are released.

24. The second network device according to any one of claims 13 to 23, wherein: The first network device is a central unit of a base station; and The second network device is a distributed unit of a base station.

25. A first network device, comprising: at least one processor; as well as At least one memory stores instructions that, when executed by the at least one processor, cause the first network device to at least perform the following operations: Transmitting a request for a lower layer triggered handover LTM to a second network device, the request indicating: an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; receiving a response to the LTM from the second network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell, and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only switching; as well as Transmitting radio resource control RRC signaling including the TCI state and the target cell configuration to the terminal device.

26. The first network device according to claim 25, wherein: The first network device is a central unit of a base station; and The second network device is a distribution unit of a base station.

27. A method for communication, comprising: At a terminal device, receiving radio resource control RRC signaling from a first network device, including: (i) a transmission configuration indicator TCI state associated with a beam for a target cell provided by a second network device, and (ii) a target cell configuration for a lower layer triggered handover LTM, wherein the TCI state is configured for beam-only handover; Based on the TCI state and a first handover command from the second network device, performing a first handover from the beam for the source cell provided by the second network device to the beam for the target cell; and Based on the first handover command or the second handover command from the second network device, a second handover from the source cell configuration to the target cell configuration is performed.

28. A method for communication, comprising: At the second network device, receiving a request for a lower layer triggered handover LTM from the first network device, the request indicating: an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; transmitting a response to the LTM to the first network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for the target cell and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only switching; as well as A first switching command for beam switching and a second switching command for configuration switching are transmitted to the terminal device.

29. A method for communication, comprising: At the first network device, transmitting a request for a lower layer triggered handover LTM to the second network device, the request indicating: an early beam handover for the LTM and a soft handover reference cell to a target cell provided by the second network device; receiving a response to the LTM from the second network device, the response comprising: (i) a transmission configuration indicator (TCI) state associated with a beam for a target cell, and (ii) a target cell configuration for the LTM, wherein the TCI state is configured for beam-only switching; as well as Transmitting radio resource control RRC signaling including the TCI state and the target cell configuration to the terminal device.

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