Resource handling in cell handover

Abstract

The embodiment of the invention relates to resource processing in cell handover, in particular to a method and device for processing contention-free random access (CFRA) resources in cell handover and a computer readable storage medium. In one method, a first device receives, from a second device, a configuration indicating CFRA resources for at least one candidate cell. The first device receives, from the second device, a cell handover command toward the first candidate cell. If it is determined that the first cell handover to the first candidate cell fails, the first apparatus determines a second candidate cell for a second cell handover. The second candidate cell is one of the at least one candidate cell. The first device then discards CFRA resources for the second candidate cell.

Description

Technical Field

[0001] Various exemplary embodiments of the present disclosure relate generally to the field of telecommunications, and more particularly to methods, apparatuses, and computer-readable storage media for handling contention-free random access (CFRA) resources in cell handover. Background Art

[0002] The Layer 1 or Layer 2 (L1 / L2) triggered mobility (LTM) procedure is provided for handover of a terminal device (e.g., a UE) from a source cell to a target cell. In the LTM procedure, a network device (e.g., a gNB) receives a Layer 1 measurement report from the UE. Based on the L1 measurement report, the gNB changes the UE's serving cell using a cell handover command signaled via a Medium Access Control Control Element (MAC CE). The cell handover command indicates the LTM candidate configurations previously prepared by the gNB and provided to the UE via Radio Resource Control (RRC) signaling. The UE then switches to the target configuration based on the cell handover command. The LTM procedure can be used to reduce mobility latency. Summary of the Invention

[0003] In a first aspect of the present disclosure, a first apparatus is provided. The first apparatus includes: 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 at least: receive from a second apparatus a configuration indicating CFRA resources for at least one candidate cell; receive from the second apparatus a cell handover command toward the first candidate cell; if a first cell handover to the first candidate cell is determined to have failed, determine a second candidate cell for a second cell handover, the second candidate cell being included in the at least one candidate cell; and discard the CFRA resources for the second candidate cell.

[0004] In a second aspect of the present disclosure, a second apparatus is provided. The second apparatus includes: 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 at least: send to a first apparatus an instruction indicating a configuration of CFRA resources for at least one candidate cell; and send to the first apparatus an instruction indicating whether the CFRA resources for a second candidate cell, included in the at least one candidate cell, are permitted to be used for a second cell handover if a first cell handover to the first candidate cell fails.

[0005] In a third aspect of the present disclosure, a method is provided. The method includes: receiving, from a second device, a configuration indicating CFRA resources for at least one candidate cell; receiving, from the second device, a cell handover command toward a first candidate cell; if it is determined that the first cell handover to the first candidate cell has failed, determining a second candidate cell for a second cell handover, the second candidate cell being included in the at least one candidate cell; and discarding the CFRA resources for the second candidate cell.

[0006] In a fourth aspect of the present disclosure, a method is provided. The method includes: sending a configuration indicating CFRA resources for at least one candidate cell to a first device; and sending an indication to the first device indicating whether the CFRA resources for a second candidate cell are allowed to be used for a second cell handover if a first cell handover to the first candidate cell fails, the second candidate cell being included in the at least one candidate cell.

[0007] In a fifth aspect of the present disclosure, a first apparatus is provided. The first apparatus includes: a component for receiving, from a second apparatus, an indication of configuration of CFRA resources for at least one candidate cell; a component for receiving, from the second apparatus, a cell handover command toward the first candidate cell; a component for determining, if a first cell handover to the first candidate cell fails, a second candidate cell for second cell handover, the second candidate cell being included in the at least one candidate cell; and a component for discarding the CFRA resources for the second candidate cell.

[0008] In a sixth aspect of the present disclosure, a second apparatus is provided. The second apparatus includes: a component for sending an indication of configuration of CFRA resources for at least one candidate cell to a first apparatus; and a component for sending an indication to the first apparatus, the indication indicating whether the CFRA resources for a second candidate cell are allowed to be used for a second cell handover if a first cell handover to the first candidate cell fails, the second candidate cell being included in the at least one candidate cell.

[0009] In a seventh aspect of the present disclosure, a computer-readable medium is provided, wherein the computer-readable medium includes instructions stored thereon for causing a device to at least execute the method according to the third aspect.

[0010] In an eighth aspect of the present disclosure, a computer-readable medium is provided, wherein the computer-readable medium includes instructions stored thereon for causing a device to at least execute the method according to the fourth aspect.

[0011] 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

[0012] Some example embodiments may now be described with reference to the accompanying drawings, in which:

[0013] Figure 1 shows an example communication environment in which example embodiments of the present disclosure may be implemented;

[0014] Figure 2 shows a signaling flow for processing CFRA resources according to some example embodiments of the present disclosure;

[0015] Figure 3 An example LTM cell handover command medium access control (MAC) control element (CE) is shown;

[0016] Figure 4A shows a signaling flow for processing CFRA resources according to some example embodiments of the present disclosure;

[0017] Figure 4B shows a signaling flow for processing CFRA resources according to some example embodiments of the present disclosure;

[0018] Figure 5 A flowchart illustrating a method implemented at a first device according to some example embodiments of the present disclosure is shown;

[0019] Figure 6 A flowchart illustrating a method implemented at a second device according to some example embodiments of the present disclosure is shown;

[0020] Figure 7 shows a simplified block diagram of a device suitable for implementing an example embodiment of the present disclosure; and

[0021] Figure 8 A block diagram of an example computer-readable medium is shown, according to some example embodiments of the present disclosure.

[0022] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0023] The principles of the present disclosure can now be described with reference to some example embodiments. It should be understood that these embodiments are described only for illustrative purposes and to help those skilled in the art understand and implement the present disclosure, and do not imply any limitation on the scope of the present disclosure. In addition to the methods described below, the embodiments described herein can be implemented in various ways.

[0024] 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.

[0025] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment necessarily includes the particular feature, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is considered within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0026] It will be understood that although the terms "first," "second," and the like may be used in front of nouns to describe various elements herein, 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 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. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0027] As used herein, “at least one of: ” and “at least one of ” and similar expressions (where a list of two or more elements is connected by “and” or “or”) refer to at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0028] As used herein, unless explicitly stated otherwise, performing a step “in response to A” does not mean performing the step immediately after “A” occurs, but may include one or more intermediate steps.

[0029] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the example embodiments. As used herein, unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" are intended to include the plural forms as well. It will also be understood that when used herein, the terms "comprise," "including," "having," "containing," "include," and / or "comprising" 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.

[0030] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware circuit implementations only (such as implementations within analog and / or digital circuitry only) and (b) a combination of hardware circuitry and software such as (if applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) any portion of a hardware processor with software (including a digital signal processor, software, and memory that work together to enable a device such as a mobile phone or server to perform various functions); and (c) a hardware circuit and / or processor, such as a microprocessor or portion of a microprocessor, that requires software (e.g., firmware) for operation, but in which the software may not be present when not required for operation.

[0031] This definition of "circuitry" applies to all uses of the term in this application, including any claims. As another example, as used in this application, the term "circuitry" also covers an implementation of merely a hardware circuit or processor (or processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example, and if applicable to a particular claim element, the term "circuitry" also covers 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.

[0032] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, communication between terminal devices and network devices in the communication network can be performed according to any suitable generation communication protocol, including but not limited to 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 protocol currently known or developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communications, there may of course be future types of communication technologies and systems that can implement the present disclosure. It should not be considered that the scope of the present disclosure is limited to the aforementioned systems.

[0033] 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 from it. 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 NR NB (also known as a gNB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), a repeater, an integrated access and backhaul (IAB) node, a low-power node (such as a femto, a micro), a non-terrestrial network (NTN) or a non-terrestrial 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, etc.), depending on the terminology and technology applied. In some example embodiments, the radio access network (RAN) split architecture includes a centralized unit (CU) and a distributed unit (DU) at an IAB donor node. The IAB node includes a mobile terminal (IAB-MT) portion that behaves like a UE towards a parent node, while the DU portion of the IAB node behaves like a base station towards a next-hop IAB node.

[0034] 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, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS) or access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices such as digital cameras, game terminal devices, music storage and playback devices, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop mounted devices (LMEs), USB dongles, smart devices, wireless customer premises equipment (CPEs), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain environments), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. The terminal device may also correspond to the mobile terminal (MT) portion of an IAB node (eg, a relay node).In the following description, the terms "terminal device," "communication device," "terminal," "user equipment," and "UE" may be used interchangeably.

[0035] As used herein, the terms "resources," "transmission resources," "resource blocks," "physical resource blocks" (PRBs), "uplink resources," or "downlink resources" may refer to any resources used to perform communication (e.g., communication between a terminal device and a network device), such as resources in the time domain, resources in the frequency domain, resources in the spatial domain, resources in the code domain, or any other combination of time domain, frequency domain, spatial domain, and / or code domain resources that enable communication. Hereinafter, unless explicitly stated otherwise, resources in the frequency domain and the time domain may be used as examples of transmission resources for describing some example embodiments of the present disclosure. Note that the example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0036] Figure 1 An example communication environment 100 is shown in which example embodiments of the present disclosure may be implemented. In the communication environment 100, a plurality of communication devices including a first apparatus 110 and a second apparatus 120 may communicate with each other.

[0037] exist Figure 1 In the example of FIG1 , the second device 120 has a certain coverage area, which can be referred to as a service area or a source cell. The first device 110 is located in a cell managed by the second device 120. In the communication environment 100, the second device 120 can communicate data and control information with the first device 110.

[0038] In some example embodiments, if first device 110 is a terminal device and second device 120 is a network device, the link from second device 120 to first device 110 is referred to as a downlink (DL), and the link from first device 110 to second device 120 is referred to as an uplink (UL). In the DL, second device 120 is a transmitting (TX) device (or transmitter), and first device 110 is a receiving (RX) device (or receiver). In the UL, first device 110 is a TX device (or transmitter), and second device 120 is an RX device (or receiver).

[0039] It should be understood that Figure 1 The number of devices and their connections shown in FIG is for illustration purposes only and does not imply any limitation. Communication environment 100 may include any suitable number of devices configured to implement example embodiments of the present disclosure.

[0040] Hereinafter, for the purpose of illustration, some example embodiments are described in which the first device 110 operates as a terminal device and the second device 120 operates as a network device. However, in some example embodiments, the operations described in conjunction with the terminal device may be implemented at a network device or other device, and the operations described in conjunction with the network device may be implemented at a terminal device or other device.

[0041] Communications in the communication environment 100 may be implemented according to any suitable communication protocol, including, but not limited to, first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), fifth generation (5G), sixth generation (6G), and the like cellular communication protocols, wireless local area network communication protocols such as Institute of Electrical and Electronics Engineers (IEEE) 802.11, and / or any other protocol currently known or developed in the future. Furthermore, communications may utilize any suitable wireless communication technology, including, 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 access (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM), and / or any other technology currently known or developed in the future.

[0042] As mentioned above, time-based handover failure procedures are supported in NR. Except in certain conditional handover (CHO), dual active protocol stack (DAPS) handover or LTM cell handover scenarios, the radio resource control (RRC) connection re-establishment procedure is used to recover from handover failure.

[0043] In a CHO scenario, when the initial CHO attempt fails or a handover fails, the terminal device performs cell selection. If the selected cell is a CHO candidate and the network device has configured the terminal device to attempt CHO after a handover / CHO failure, the terminal device attempts CHO once; otherwise, it performs a reestablishment procedure.

[0044] In the DAPS handover scenario, when the DAPS handover fails, the terminal device falls back to the source cell configuration, restores the connection with the source cell, and if the source link is not released, reports the DAPS handover failure via the source link without triggering RRC connection reestablishment.

[0045] In an LTM cell handover scenario, when the initial LTM execution attempt fails or the handover fails, the terminal device performs cell selection. If the selected cell is an LTM candidate cell and if the network device has configured the terminal device to attempt LTM after an LTM execution failure, the terminal device attempts LTM execution once, otherwise it performs the reestablishment process.

[0046] LTM is a process in which a network device receives L1 measurement reports from a terminal device and, based on the received L1 measurement reports, changes the serving cell if the terminal device issues a cell handover command. The cell handover command is signaled via a MAC CE. The cell handover command indicates a candidate LTM configuration that the network device has previously prepared and provided to the terminal device via RRC signaling. The terminal device then switches to the target configuration based on the cell handover command. The LTM process can be used to reduce mobility latency.

[0047] When configured by the network equipment, the transmission configuration index (TCI) state of one or more cells different from the current serving cell can be activated. For example, the TCI state of LTM candidate cells can be activated in advance before any of these cells become the serving cell. This allows the terminal device to synchronize with the downlink (DL) of those LTM candidate cells, thereby facilitating faster cell handover to one of those cells when a cell handover is triggered.

[0048] When configured by the network equipment, an uplink (UL) timing advance (TA) acquisition procedure (called early TA acquisition) may be initiated for one or more cells that are different from the current serving cell. TA or N TA =0, no early TA acquisition process is required. The network device can request the terminal device to perform an early TA acquisition process on the candidate cell before cell switching. The early TA acquisition process is triggered by a physical downlink control channel (PDCCH) command or implemented by UE-based TA measurement configured by RRC. In the former case, the network device to which the candidate cell belongs calculates the TA value and sends it to the network device. The serving cell sends the TA value in the LTM cell switching command MAC CE when triggering LTM cell switching. In the latter case, the terminal device performs TA measurement on the candidate cell after being configured by RRC. The exact time when the terminal device performs TA measurement depends on the implementation of the terminal device. The terminal device applies the TA value measured by the terminal device itself via TA measurement and performs LTM without random access channel (RACH) when receiving the cell switching command. Alternatively, the TA value can be obtained from the network device in the LTM cell switching command MAC CE without acquiring TA in advance.

[0049] Depending on the availability of a valid TA value, the terminal device performs either RACH-free LTM cell handover or RACH-based LTM cell handover. If a TA value is provided in the cell handover command, the terminal device applies the TA value as instructed by the network device. If UE-based TA measurement is configured but no TA value is provided in the cell handover command, the terminal device applies the TA value measured by the terminal device if its own measurement is available. At the same time, the terminal device performs RACH-free LTM cell handover when it receives a cell handover command. If no valid TA value is available, the terminal device performs RACH-based LTM cell handover.

[0050] Regardless of whether the terminal device is configured with UE-based TA measurements for a candidate cell, it follows the PDCCH command, which includes requesting a random access procedure from the candidate cell. This also applies to candidate cells for which the terminal device is able to measure the TA value itself. Alternatively or additionally, regardless of whether the terminal device has performed a random access procedure for the candidate cell, it follows the UE-based measurement configuration if configured by the network equipment.

[0051] For LTM without RACH, the terminal device uses a configured grant or a dynamic grant to access the target cell. The configured grant is provided in the LTM candidate configuration. The terminal device selects the configured grant opportunity associated with the beam indicated in the cell handover command. When an LTM cell handover is initiated to the target cell, the terminal device begins monitoring the PDCCH on the target cell for dynamic scheduling. Before completing the LTM without RACH procedure, if the terminal device does not have valid physical uplink control channel (PUCCH) resources to trigger a scheduling request (SR), the terminal device will not trigger the random access procedure.

[0052] There are several principles that can be applied to LTM. One principle is to maintain security keys during LTM cell handover. Another principle is to support subsequent LTM.

[0053] LTM supports intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. LTM supports intra-frequency and inter-frequency mobility, including mobility to an inter-frequency cell that is not the current serving cell. LTM is supported only for licensed spectrum. The following scenarios are supported: - PCell changes in non-CA and non-DC scenarios; -Pcell and Scell changes in CA scenarios; - Dual connectivity scenario, Pcell and MCG Scell changes, and intra-SN PSCell and SCG Scell changes without MN participation. LTM for simultaneous Pcell and PSCell changes is not supported.

[0054] Although the terminal device has stored the LTM candidate configuration, the terminal device may also execute any layer 3 (L3) switching command sent by the network device.

[0055] The CFRA resources provided by the RRC may be pre-provisioned to the UE for any LTM candidate in ltm-Config (R2-2313672), (TS 38.331 v18.0.0). Table 1 shows an example of a portion of the LTM configuration. Table 1

[0056] The above RRCReconfiguration includes a ReconfigurationWithSync information element (IE) for LTM. Table 2 shows an example of RRC reconfiguration. Table 2

[0057] In the above LTM cell handover scenario, if the initial LTM attempt (commanded by the network device using the LTM cell handover command MAC CE) fails, the terminal device selects a new cell. If the new cell is configured as an LTM candidate cell, the terminal device performs the LTM cell handover procedure on the selected cell.

[0058] During the RRC connection reestablishment procedure, after performing cell selection, an LTM cell handover procedure for the selected LTM candidate cell may be performed in the following circumstances, for example but not limited to: a) if the cell selection is triggered by detecting a radio link failure of a master cell group (MCG) or a reconfiguration with a synchronization failure of an MCG or mobility from an NR failure; b) if an LTM handover attempt is configured; and c) if the selected cell is one of the LTM candidate cells in the LTM candidate information element (IE) within the VarLTM-Config associated with the MCG.

[0059] In traditional LTM cell handover, the network device triggers LTM cell handover using the LTM CSC MAC CE, and the terminal device performs LTM cell handover to the indicated target cell. However, LTM cell handover may fail. As described above, in the event of LTM cell handover failure, the terminal device triggers the LTM recovery process and performs the cell selection process to select a cell. If the selected cell is an LTM candidate cell, the terminal device performs the LTM cell handover process to the selected cell. If the LTM recovery process is successful, the terminal device retains the LTM configuration initially configured by the network device.

[0060] In this case, the terminal device may have been pre-configured with CFRA resources by the network equipment to be used for the selected cell during the LTM recovery process. Since the network instructs the LTM cell handover process to a different target cell, the NW may have reallocated the pre-configured CFRA resources to another terminal device. Therefore, when the RA process is triggered based on the cell handover process, the terminal device applies the pre-configured CFRA resources during the RA process, which may be problematic and unexpected for the network. In addition, the issue of how to handle the pre-configured CFRA resources allocated in the LTM CSC MAC CE when the LTM cell handover fails and / or the LTM recovery process is triggered needs to be addressed.

[0061] According to some example embodiments of the present disclosure, a solution for handling CFRA resources is proposed. In this solution, a terminal device receives a configuration indicating CFRA resources for at least one candidate cell, and optionally has an indication for indicating whether CFRA resources for a second candidate cell are allowed to be used for a second cell handover in the event that a first cell handover to the first candidate cell fails. The terminal device also receives a cell handover command toward the first candidate cell. If the first cell handover to the first candidate cell fails, the terminal device determines a second candidate cell for the second cell handover included in at least one candidate cell. The terminal device then discards the CFRA resources for the second candidate cell. In this way, the CFRA resources pre-configured for the LTM candidate cell can be processed during the LTM recovery process (i.e., the LTM cell handover process triggered after RLF and cell selection), and resource conflicts can be avoided.

[0062] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0063] Figure 2 FIG2 shows a signaling flow 200 for processing random access resources according to some example embodiments of the present disclosure. For the purpose of discussion, reference will be made to FIG2 . Figure 1Discuss signaling flow 200. The signaling flow involves a first device 110 and a second device 120. For illustration purposes, some example embodiments may be described in which the first device 110 operates as a terminal device (e.g., UE) and the second device 120 operates as a network device (e.g., gNB).

[0064] In signaling flow 200, second device 120 sends (205) to first device 110 a configuration indicating CFRA resources. The CFRA resources are for at least one candidate cell. The candidate cell may serve as a candidate for a cell handover or handover procedure. In some example embodiments, the cell handover may be an LTM cell handover. In this case, the candidate cell may be used for the LTM cell handover. In the case where the cell handover is an LTM cell handover, the configuration received by first device 110 may be an LTM configuration.

[0065] In some example embodiments, the CFRA resource may be a 4-step random access (RA) resource or a 2-step RA resource. According to some aspects, the RACH may include a 2-step RA procedure and / or a 4-step RA procedure. For example, in Rel-15, the 4-step RA procedure is configured for the UE to perform its initial access. In Rel-16, the 4-step RA and 2-step RA procedures may be configured within a cell for the UE to perform its initial access. Different RO and / or preamble combinations may be used to distinguish between 2-step RACH resources and 4-step RACH resources. According to some aspects, the 2-step RACH procedure and the 4-step RA procedure may be based on, for example, Technical Specification (TS) 38.211 Section 6.3.3.2, TS 38.213 Section 8, and / or TS 38.321 Section 5.1.

[0066] The first device 110 receives 210 a configuration from the second device 120. Thus, the second device 120 has knowledge of the CFRA resources for at least one candidate cell.

[0067] like Figure 2 As shown, the second device 120 sends (215) a cell handover command toward the first candidate cell to the first device 110. The first device 110 also receives (220) the cell handover command from the second device 120. In some example embodiments, the first device 110 may determine the first candidate cell based on the target configuration index in the cell handover command. Thus, upon receiving the (220) cell handover command, the first device 110 will know the target cell of the upcoming cell handover (in this case, the first candidate cell) and may perform the cell handover accordingly (also referred to as "first cell handover" for the sake of discussion).

[0068] The following will take the Third Generation Partnership Project (3GPP) TS 38.321 v18.0.0 as an example to discuss an example implementation of the LTM cell handover command in Table 3. Table 3

[0069] The following will take 3GPP TS38.321 v18.0.0 as an example to discuss an example implementation of the LTM cell handover command MAC CE in Table 4. Table 4

[0070] Figure 3 Corresponding to Table 4. Figure 3 An example of an LTM Cell Handover Command MAC CE is shown. The contents in the LTM Cell Handover Command MAC CE have been discussed with reference to Table 4 as described above.

[0071] Still refer to Figure 2 If the first cell handover to the first candidate cell fails, the first device 110 determines (225) a second candidate cell for a second cell handover. The second candidate cell is included in the at least one candidate cell. In some example embodiments, the first cell handover may be an LTM cell handover. Similar to the first cell handover, the second cell handover may also be an LTM cell handover.

[0072] Then, first device 110 discards (230) the CFRA resources used for the second candidate cell. As used herein, the term "discard" may refer to the release of CFRA resources, or retaining CFRA resources but not using any resources other than for the RA process for cell handover (such as the first cell handover and / or the second cell handover). In some example embodiments, first device 110 may not be allowed to use pre-configured CFRA resources for the LTM recovery process, but first device 110 retains their configuration.

[0073] In some example embodiments, after discarding the CFRA resources for the second candidate cell, the first device 110 may perform a second cell handover to the second candidate cell based on contention-based random access (CBRA) resources.

[0074] In some example embodiments, first device 110 may discard CFRA resources associated with the second candidate cell. In this case, first device 110 may discard CFRA resources only for the selected LTM candidate cell. Alternatively or additionally, first device 110 may discard CFRA resources associated with all candidate cells in the at least one candidate cell. That is, first device 110 may discard CFRA resources for all LTM candidate cells. As another alternative, first device 110 may discard CFRA resources associated with a group of cells in the at least one candidate cell. In some examples, this group may be configured by second device 120.

[0075] In some example embodiments, the first device 110 may discard the CFRA resources at a first time point when the second cell handover is initiated, at a second time point when the first cell handover fails, or at a third time point when the random access procedure performed for the second cell handover is completed. In some example embodiments, the first device 110 may discard the pre-configured CFRA resources when initiating the LTM cell handover procedure for LTM recovery (i.e., after cell selection) or when the LTM cell handover fails (i.e., before cell selection) (RLF). In one example, the first device 110 may discard the CFRA resources for the selected cell for LTM recovery only upon completion of the random access procedure performed for the LTM recovery procedure.

[0076] The following Figure 4A A signaling flow 400A for processing CFRA resources according to some example embodiments of the present disclosure is shown. The signaling flow 400A involves a first device 110 and a second device 120. For illustrative purposes, some example embodiments may be described in which the first device 110 operates as a terminal device (e.g., a UE) and the second device 120 operates as a network device (e.g., a gNB).

[0077] like Figure 4A As shown, the second device 120 sends (405) a configuration (e.g., an LTM configuration) to the first device 110. The LTM configuration can be sent via an RRCReconfiguration message and can at least indicate CFRA resources for the second candidate cell. In some implementations, the LTM configuration can also indicate CFRA resources for candidate cells other than the second candidate cell. The first device 110 receives (410) the LTM configuration and thus knows at least the CFRA resources for the second candidate cell.

[0078] The second device 120 also sends (415) an LTM cell handover command to the first device 110 to instruct the first device 110 to switch to the first candidate cell. The first device 110 receives (420) the LTM cell handover command and then performs a first cell handover toward the first candidate cell. In some cases, the first device 110 determines (425) that the first cell handover has failed. The first device 110 then performs (430) cell selection to select the second candidate cell. After cell selection, the first device 110 may perform an LTM recovery procedure and / or another cell handover toward the second candidate cell (also referred to as a second cell handover). The first device 110 then discards (435) the CFRA resources explicitly signaled for the second candidate cell and performs (440) an LTM cell handover to the second candidate cell using CBRA resources.

[0079] In some example embodiments, the second device 120 may send an indication to the first device 110. That is, the indication may be included in the configuration sent by the second device 120. The indication may indicate whether the CFRA resources for the second candidate cell are allowed to be used for the second cell handover in the event that the first cell handover to the first candidate cell fails. In this case, the second candidate cell is included in the at least one candidate cell. After receiving such an indication, if the CFRA resources are not allowed to be used for the second cell handover, the first device 110 discards the CFRA resources for the second candidate cell. In this case, the second device 120 may indicate whether the pre-configured CFRA resources are allowed to be used for the LTM recovery process. In some example embodiments, if the CFRA resources are not allowed to be used for the selected LTM candidate cell, the first device 110 may discard the CFRA resources associated with the selected LTM candidate cell.

[0080] In some example embodiments, the indication may be candidate cell specific, terminal device specific, common to all candidate cells, or specific to a group of candidate cells. That is, the indication may be LTM candidate cell specific or UE specific (i.e., a common indication for all LTM candidates).

[0081] In some example embodiments, the indication may be obtained from a cell handover command or received via RRC signaling. Whether the first device 110 is allowed to use the CFRA resources indicated in the LTM CSC MAC CE (in the case where the selected cell for the LTM recovery procedure is the target cell of the LTM procedure) for the LTM recovery procedure is indicated as another indication in the LTM CSC MAC CE or separately in the RRC configuration.

[0082] In some example embodiments, the indication may also indicate whether to discard the CFRA resources for the second candidate cell or for all candidate cells in at least one candidate cell. Further, the indication may include a time point at which the CFRA resources are discarded. The time point may be the first time point at which the second cell handover is initiated. Alternatively, the time point may be the second time point at which the first cell handover fails. In other cases, the time point may indicate that the CFRA resources are discarded when the random access procedure performed for the second cell handover is completed. Therefore, (in the case where the selected cell for the LTM recovery procedure is the target cell of the LTM procedure) the CFRA resources indicated in the LTM CSC MAC CE may always be discarded when the LTM cell handover fails or when the LTM recovery procedure is initiated.

[0083] In some further example embodiments, the discarded CFRA resources may not include CFRA resources used for beam failure recovery (BFR). Therefore, the first terminal device 110 may not discard BFR CFRA resources (if any) configured for the selected LTM candidate cell.

[0084] In some example embodiments, at least one of the first cell handover and the second cell handover may be a layer 1 or layer 2 (L1 / L2) triggered mobility (LTM) cell handover. As an example, the first apparatus may include a terminal device, and the second apparatus may include a network device.

[0085] refer to Figure 4B Further discussing the above embodiment, Figure 4B A signaling flow 400B for processing CFRA resources according to some example embodiments of the present disclosure is shown. The signaling flow 400B involves a first device 110 and a second device 120. For illustrative purposes, some example embodiments may be described in which the first device 110 operates as a terminal device (e.g., a UE) and the second device 120 operates as a network device (e.g., a gNB).

[0086] like Figure 4B As shown, the second device 120 sends (445) a configuration (e.g., an LTM configuration) to the first device 110. The LTM configuration can be sent via an RRCReconfiguration message and can at least indicate CFRA resources for the second candidate cell. In some implementations, the LTM configuration can also indicate CFRA resources for candidate cells other than the second candidate cell. The first device 110 receives (450) the LTM configuration and thus knows at least the CFRA resources of the second candidate cell.

[0087] like Figure 4BAs shown, the second device 120 sends (455) an indication to the first device 110, indicating whether the CFRA resources used for the second cell handover are allowed to be used for the second cell handover if the first cell handover to the first candidate cell fails. This indication can be included in the LTM configuration or can be sent separately, for example, via separate RRC signaling. The first device 110 receives (460) the indication from the second device 120. Therefore, the first device 110 can know whether the CFRA resources can be discarded.

[0088] like Figure 4B As shown, the second device 120 may also send (465) a cell switching command (e.g., an LTM cell switching command) to the first device 110 to instruct the first device 110 to switch to the first candidate cell. Figure 4B In the illustrated example embodiment, the indication of whether CFRA resources are allowed to be used for the second cell handover is sent (455) via a separate message or signaling, but this is merely an example and does not imply any limitation. In other example embodiments, the indication may be sent via a cell handover command or in other suitable manners.

[0089] Regarding the first device 110, it may receive (470) a cell handover command and then determine (475) that the LTM cell handover to the first candidate cell has failed. The first device 110 may then perform (480) cell selection to select a second candidate cell. After the cell selection, the first device 110 may perform an LTM recovery procedure and / or a cell handover to the second candidate cell. The first device 110 may determine (485) whether to discard the explicitly signaled CFRA resources based on the indication.

[0090] If the first device 110 determines to discard the CFRA resources, the first device 110 performs (490) an LTM cell handover to the second candidate cell using the BCRA resources. Alternatively, if it is determined not to discard the CFRA resources, the first device 110 performs (490) an LTM cell handover to the second candidate cell using the CFRA resources.

[0091] Some example implementation options for TS 38.331 for example embodiments of the present disclosure are provided in Table 5 below. Table 5

[0092] Some example implementation options of TS 38.321 for example embodiments of the present disclosure are provided in Table 6 below. Table 6

[0093] In view of the above, the NW can immediately reuse the CFRA resources configured for the LTM candidate cell configured for the UE performing LTM cell handover to another UE. In addition, the NW has a component that controls whether the UE uses the CFRA resources for LTM recovery.

[0094] Figure 5 FIG. 5 is a flow chart illustrating an example method 500 implemented at a first device according to some example embodiments of the present disclosure. For discussion purposes, Figure 1 The method 500 is described from the perspective of the first device 110.

[0095] At block 510 , the first device 110 receives a configuration indicating CFRA resources for at least one candidate cell from a second device.

[0096] At block 520 , the first device 110 receives a cell handover command from the second device toward the first candidate cell.

[0097] At block 530 , if it is determined that the first cell handover to the first candidate cell has failed, the first device 110 determines a second candidate cell for a second cell handover, the second candidate cell being included in the at least one candidate cell.

[0098] At block 540 , the first device 110 discards the CFRA resources for the second candidate cell.

[0099] In some example embodiments, the method 500 further includes performing a second cell handover to a second candidate cell based on contention-based random access (CBRA) resources.

[0100] In some example embodiments, the CFRA resource is a 4-step random access (RA) resource or a 2-step RA resource.

[0101] In some example embodiments, the method 500 further comprises discarding CFRA resources associated with the second candidate cell, or discarding CFRA resources associated with all candidate cells of the at least one candidate cell.

[0102] In some example embodiments, the method 500 further includes discarding the CFRA resource at a first time point when the second cell handover is initiated, a second time point when the first cell handover fails, or a third time point when the random access procedure performed for the second cell handover is completed.

[0103] In some example embodiments, the method 500 further includes: receiving an indication from the second apparatus indicating whether CFRA resources are allowed for the second cell handover; and discarding the CFRA resources for the second candidate cell if it is determined that CFRA resources are not allowed for the second cell handover.

[0104] In some example embodiments, the indication is candidate cell specific or terminal device specific, or common to all candidate cells.

[0105] In some example embodiments, the indication is obtained from a cell handover command or received via RRC signaling.

[0106] In some example embodiments, the indication is further used to indicate whether CFRA resources are discarded for the second candidate cell or for all candidate cells in the at least one candidate cell.

[0107] In some example embodiments, the indication is also used to indicate a time point for discarding CFRA resources, which time point includes one of the following: a first time point when the second cell handover is initiated, a second time point when the first cell handover fails, or a third time point when the random access procedure performed for the second cell handover is completed.

[0108] In some example embodiments, the discarded CFRA resources do not include CFRA resources used for beam failure recovery.

[0109] In some example embodiments, at least one of the first cell handover and the second cell handover is a layer 1 or layer 2 (L1 / L2) triggered mobility (LTM) cell handover.

[0110] In some example embodiments, the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

[0111] Figure 6 FIG. 6 is a flow chart illustrating an example method 600 implemented at a second device according to some example embodiments of the present disclosure. Figure 1 The method 600 is described from the perspective of the second device 120.

[0112] At block 610 , the second device 120 sends a configuration indicating CFRA resources for at least one candidate cell to the first device.

[0113] At block 620 , the second device 120 sends an indication to the first device indicating whether the CFRA resource for the second candidate cell is allowed to be used for the second cell handover if the first cell handover to the first candidate cell fails, the second candidate cell being included in the at least one candidate cell.

[0114] In some example embodiments, the CFRA resource is a 4-step random access (RA) resource or a 2-step RA resource.

[0115] In some example embodiments, the indication is candidate cell specific or terminal device specific, or common to all candidate cells.

[0116] In some example embodiments, the indication is sent via a cell handover command towards the first candidate cell or via radio resource control (RRC) signaling.

[0117] In some example embodiments, the indication is further used to indicate whether the CFRA resources are discarded for the second candidate cell or for all candidate cells of the at least one candidate cell.

[0118] In some example embodiments, the indication is also used to indicate a time point for discarding CFRA resources, which time point includes one of the following: a first time point when the second cell handover is initiated, a second time point when the first cell handover fails, or a third time point when the random access procedure performed for the second cell handover is completed.

[0119] In some example embodiments, the discarded CFRA resources do not include CFRA resources used for beam failure recovery.

[0120] In some example embodiments, at least one of the first cell handover or the second cell handover is a layer 1 or layer 2 (L1 / L2) triggered mobility (LTM) cell handover.

[0121] In some example embodiments, the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

[0122] In some example embodiments, a first device (eg, Figure 1 The first device 110 in the embodiment may include a component for performing the corresponding operation of the method 500. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit system or a software module. The first device may be implemented as Figure 1 The first device 110 or the first device 110 included in Figure 1 In the first device 110.

[0123] In some example embodiments, a first apparatus includes: means for receiving, from a second apparatus, a configuration indicating CFRA resources for at least one candidate cell; means for receiving, from the second apparatus, a cell handover command toward the first candidate cell; means for determining, if it is determined that the first cell handover to the first candidate cell has failed, a second candidate cell for a second cell handover, the second candidate cell being included in the at least one candidate cell; and means for discarding the CFRA resources of the second candidate cell.

[0124] In some example embodiments, the first apparatus further comprises means for performing a second cell handover to a second candidate cell based on contention-based random access (CBRA) resources.

[0125] In some example embodiments, the CFRA resource is a 4-step random access (RA) resource or a 2-step RA resource.

[0126] In some example embodiments, the first apparatus further comprises means for discarding CFRA resources associated with the second candidate cell, or means for discarding CFRA resources associated with all candidate cells of the at least one candidate cell.

[0127] In some example embodiments, the first apparatus further includes a component for discarding CFRA resources at a first time point when the second cell handover is initiated, or a second time point when the first cell handover fails, or a third time point when the random access procedure performed for the second cell handover is completed.

[0128] In some example embodiments, the first apparatus further includes: means for receiving an indication from the second apparatus indicating whether CFRA resources are permitted for the second cell handover; and means for discarding the CFRA resources for the second candidate cell if it is determined that the CFRA resources are not permitted for the second cell handover.

[0129] In some example embodiments, the indication is candidate cell specific or terminal device specific, or common to all candidate cells.

[0130] In some example embodiments, the indication is obtained from a cell handover command or received via radio resource control (RRC) signaling.

[0131] In some example embodiments, the indication is further used to indicate whether the CFRA resources are discarded for the second candidate cell or for all candidate cells of the at least one candidate cell.

[0132] In some example embodiments, the indication is also used to indicate a time point for discarding CFRA resources, which time point includes one of the following: a first time point when the second cell handover is initiated, a second time point when the first cell handover fails, or a third time point when the random access procedure performed for the second cell handover is completed.

[0133] In some example embodiments, the discarded CFRA resources do not include CFRA resources other than those used for beam failure recovery.

[0134] In some example embodiments, at least one of the first cell handover and the second cell handover is a layer 1 or layer 2 (L1 / L2) triggered mobility (LTM) cell handover.

[0135] In some example embodiments, the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

[0136] In some example embodiments, the first apparatus further comprises means for performing the method 500 or other operations of some example embodiments of the first apparatus 110. In some example embodiments, the means comprises: 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 perform the operations.

[0137] In some example embodiments, a second device (e.g., Figure 1 The second device 120 in the embodiment may include components for performing the corresponding operations of method 600. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit system or a software module. The second device may be implemented as Figure 1 The second device 120 in or included in Figure 1 In the second device 120.

[0138] In some example embodiments, the second apparatus includes: means for sending an indication of a configuration of CFRA resources for at least one candidate cell to the first apparatus; and means for sending an indication to the first apparatus indicating whether the CFRA resources for a second candidate cell are allowed to be used for a second cell handover if a first cell handover to the first candidate cell fails, the second candidate cell being included in the at least one candidate cell.

[0139] In some example embodiments, the CFRA resource is a 4-step random access (RA) resource or a 2-step RA resource.

[0140] In some example embodiments, the indication is candidate cell specific or terminal device specific, or common to all candidate cells.

[0141] In some example embodiments, the indication is sent via a cell handover command towards the first candidate cell or via radio resource control (RRC) signaling.

[0142] In some example embodiments, the indication is further used to indicate whether the CFRA resources are discarded for the second candidate cell or for all candidate cells of the at least one candidate cell.

[0143] In some example embodiments, the indication is also used to indicate a time point for discarding CFRA resources, which time point includes one of the following: a first time point when the second cell handover is initiated, a second time point when the first cell handover fails, or a third time point when the random access procedure performed for the second cell handover is completed.

[0144] In some example embodiments, the discarded CFRA resources do not include CFRA resources used for beam failure recovery.

[0145] In some example embodiments, at least one of the first cell handover or the second cell handover is a layer 1 or layer 2 (L1 / L2) triggered mobility (LTM) cell handover.

[0146] In some example embodiments, the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

[0147] In some example embodiments, the second apparatus further comprises means for performing the method 600 or other operations of some example embodiments of the second apparatus 120. In some example embodiments, the means comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause execution of the second apparatus.

[0148] Figure 7 is a simplified block diagram of a device 700 suitable for implementing an example embodiment of the present disclosure. The device 700 may be provided to implement a communication device, such as Figure 1 As shown in the figure, the device 700 includes one or more processors 710, one or more memories 720 coupled to the processor 710, and one or more communication modules 740 coupled to the processor 710.

[0149] The communication module 740 is configured for bidirectional communication. The communication module 740 has one or more communication interfaces to facilitate communication with one or more other modules or devices. A communication interface may represent any interface necessary to communicate with other network elements. In some example embodiments, the communication module 740 may include at least one antenna.

[0150] Processor 710 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 700 may have multiple processors, such as application specific integrated circuit chips, that are time slaved to a clock synchronized with a master processor.

[0151] The memory 720 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) 724, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact discs (CDs), digital video discs (DVDs), optical discs, laser discs, and other magnetic and / or optical storage devices. Examples of volatile memories include, but are not limited to, random access memory (RAM) 722 and other volatile memories that will not persist during a power outage.

[0152] The computer program 730 includes computer-executable instructions executed by the associated processor 710. The instructions of the program 730 may include instructions for performing the operations / actions of some example embodiments of the present disclosure. The program 730 may be stored in a memory (e.g., ROM 724). The processor 710 may perform any suitable actions and processes by loading the program 730 into the RAM 722.

[0153] The exemplary embodiments of the present disclosure may be implemented with the aid of a program 730, so that the device 700 may execute the following steps: Figures 2 to 6 Any process of the present disclosure discussed. The exemplary embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0154] In some example embodiments, the program 730 may be tangibly embodied in a computer-readable medium that may be included in the device 700 (such as in the memory 720) or in other storage devices accessible by the device 700. The device 700 may load the program 730 from the computer-readable medium to the RAM 722 for execution. In some example embodiments, the computer-readable medium may include any type of non-transitory storage medium, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. The term "non-transitory" as used herein is a limitation on the medium itself (i.e., tangible, not a signal), and not a limitation on data storage persistence (e.g., RAM versus ROM).

[0155] Figure 8 An example of a computer readable medium 800 is shown, which may be in the form of a CD, DVD, or other optical storage disc.The computer readable medium 800 has the program 730 stored thereon.

[0156] 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, and other aspects may be implemented in firmware or software that 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 representation, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or a controller or other computing device, or some combination thereof.

[0157] 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-transient computer-readable medium). The computer program product includes computer-executable instructions, such as those executable instructions included in a program module that are executed in a device on a target physical or virtual processor to perform any method as described above. Typically, a program module includes routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The functionality of the program modules can be combined or split between program modules as needed in various embodiments. The machine executable instructions for the program modules can be executed in local or distributed devices. In distributed devices, the program modules can be located in both local and remote storage media.

[0158] The program code for performing the method of the present disclosure can be written in any combination of one or more programming languages. The program code 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 the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0159] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform the various processes and operations described above. Examples of carriers include signals, computer-readable media, etc.

[0160] 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, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or apparatus, or any suitable combination of the foregoing. More specific examples of computer readable storage media would include an electrical connection having 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 disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0161] In addition, 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 of the operations shown be performed, in order to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be interpreted as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to a particular embodiment. Unless expressly stated otherwise, certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. Conversely, unless expressly stated otherwise, various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable subcombination.

[0162] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A first apparatus for communication, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the first device to at least: receiving, from a second apparatus, a configuration indicating contention-free random access (CFRA) resources for at least one candidate cell; receiving a cell handover command from the second device toward a first candidate cell; If it is determined that the first cell handover to the first candidate cell fails, determining a second candidate cell for a second cell handover, the second candidate cell being included in the at least one candidate cell; and The CFRA resources used for the second candidate cell are discarded.

2. The first device according to claim 1, wherein the first device is configured to: The second cell handover to the second candidate cell is performed based on contention-based random access (CBRA) resources. 3 . The first apparatus according to claim 1 , wherein the CFRA resource is a 4-step random access (RA) resource or a 2-step RA resource.

4. The first device according to claim 1, wherein the first device is configured to: discarding the CFRA resources associated with the second candidate cell, or The CFRA resources associated with all candidate cells of the at least one candidate cell are discarded.

5. The first device according to claim 1, wherein the first device is caused to: The CFRA resource is discarded at a first time point when the second cell handover is initiated, a second time point when the first cell handover fails, or a third time point when the random access procedure performed for the second cell handover is completed.

6. The first device according to claim 1, wherein the first device is caused to: receiving an indication from the second apparatus indicating whether the CFRA resource is allowed to be used for the second cell handover; and If it is determined that the CFRA resource is not allowed to be used for the second cell handover, the CFRA resource used for the second candidate cell is discarded. 7 . The first apparatus according to claim 6 , wherein the indication is candidate cell specific or terminal device specific, or common to all candidate cells.

8. The first apparatus of claim 6, wherein the indication is obtained from the cell handover command or received via radio resource control (RRC) signaling.

9. The first apparatus according to claim 6, wherein the indication is further used to indicate whether the CFRA resources are discarded for the second candidate cell or for all candidate cells among the at least one candidate cell.

10. The first apparatus according to claim 6, wherein the indication is further used to indicate a time point for discarding the CFRA resource, the time point comprising one of the following: The first time point at which the second cell handover is initiated, The second time point at which the first cell handover fails, or A third time point at which a random access procedure performed for the second cell handover is completed. 11 . The first apparatus according to claim 1 , wherein the discarded CFRA resources do not include CFRA resources used for beam failure recovery.

12. The first apparatus of claim 1, wherein at least one of the first cell handover or the second cell handover is a layer 1 or layer 2 (L1 / L2) triggered mobility (LTM) cell handover. 13 . The first apparatus according to claim 1 , wherein the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

14. A second device for communication, comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the second device to at least: sending, to the first apparatus, a configuration indicating contention-free random access (CFRA) resources for at least one candidate cell; as well as An indication is sent to the first apparatus, the indication being used to indicate whether the CFRA resource for a second candidate cell is allowed to be used for a second cell handover if a first cell handover to the first candidate cell fails, the second candidate cell being included in the at least one candidate cell. 15 . The second apparatus according to claim 14 , wherein the CFRA resource is a 4-step random access (RA) resource or a 2-step RA resource. 16 . The second apparatus according to claim 14 , wherein the indication is candidate cell specific or terminal device specific, or common to all candidate cells.

17. The second apparatus of claim 14, wherein the indication is sent via a cell handover command towards the first candidate cell or via radio resource control (RRC) signaling.

18. The second apparatus according to claim 14, wherein the indication is further used to indicate whether the CFRA resources are discarded for the second candidate cell or for all candidate cells among the at least one candidate cell.

19. The second apparatus according to claim 14, wherein the indication is further used to indicate a time point for discarding the CFRA resource, the time point comprising one of the following: The first time point at which the second cell handover is initiated, The second time point at which the first cell handover fails, or A third time point at which a random access procedure performed for the second cell handover is completed.

20. The second apparatus according to claim 14, wherein the discarded CFRA resources do not include CFRA resources used for beam failure recovery.

21. The second apparatus of claim 14, wherein at least one of the first cell handover or the second cell handover is a layer 1 or layer 2 (L1 / L2) triggered mobility (LTM) cell handover.

22. The second apparatus according to any one of claims 14 to 21, wherein the first apparatus comprises a terminal device, and the second apparatus comprises a network device.

23. A method for communication, comprising: receiving, from a second apparatus, a configuration indicating contention-free random access (CFRA) resources for at least one candidate cell; receiving a cell handover command from the second device toward a first candidate cell; If it is determined that the first cell handover to the first candidate cell fails, determining a second candidate cell for a second cell handover, the second candidate cell being included in the at least one candidate cell; and The CFRA resources used for the second candidate cell are discarded.

24. A method for communication, comprising: sending, to the first apparatus, a configuration indicating contention-free random access (CFRA) resources for at least one candidate cell; as well as An indication is sent to the first apparatus, the indication being used to indicate whether the CFRA resource for a second candidate cell is allowed to be used for a second cell handover if a first cell handover to the first candidate cell fails, the second candidate cell being included in the at least one candidate cell.

25. A first apparatus for communication, comprising: means for receiving from a second apparatus a configuration indicating contention-free random access (CFRA) resources for at least one candidate cell; means for receiving a cell handover command from the second apparatus towards a first candidate cell; means for determining a second candidate cell for a second cell handover if it is determined that the first cell handover to the first candidate cell has failed, the second candidate cell being included in the at least one candidate cell; as well as means for discarding CFRA resources for the second candidate cell.

26. A second device for communication, comprising: means for sending to the first apparatus an indication of a configuration of contention-free random access (CFRA) resources for at least one candidate cell; as well as means for sending an indication to the first apparatus, the indication indicating whether the CFRA resources for a second candidate cell are allowed to be used for a second cell handover if a first cell handover to the first candidate cell fails, the second candidate cell being included in the at least one candidate cell.

27. A computer-readable medium comprising instructions stored thereon, the instructions being configured to cause an apparatus to at least perform the method according to claim 23 or the method according to claim 24.

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