User device and user device method

Abstract

The embodiments of the present disclosure relate to a communication apparatus and method. In one aspect, a terminal device receives, from a serving cell, a DCI triggering an RA procedure on a candidate cell among a set of candidate cells that allow LTM, and transmits a preamble for the RA procedure to the candidate cell. The terminal device monitors a PDCCH on at least one of the serving cell or the candidate cell, and receives an RAR from the at least one of the serving cell or the candidate cell. In this way, the RA procedure for the candidate cell for LTM is realized.

Description

[Technical Field]

[0001] TECHNICAL FIELD Embodiments of the present disclosure relate generally to the field of telecommunications, and more particularly to an apparatus and method of communication for Random Access (RA) procedures. [Background technology]

[0002] When a user equipment (UE) moves from the coverage area of ​​one cell to the coverage area of ​​another cell, it may be necessary to change, add, or release the serving cell. Currently, it has been proposed to trigger the serving cell change, addition, or release by lower layer signaling, such as Layer 1 (L1) / Layer 2 (L2) signaling. This is also called L1 / L2 Triggered Mobility (LTM). This can reduce delay, overhead, and interruption time. However, the RA procedure for timing advance (TA) acquisition for LTM is still unclear and needs to be further studied. Summary of the Invention [Problem to be solved by the invention]

[0003] Generally, embodiments of the present disclosure provide a communication method, apparatus, and computer storage medium for RA procedures. [Means for solving the problem]

[0004] In a first aspect, a terminal device is provided, the terminal device comprising a processor configured to cause the terminal device to receive, from a serving cell, downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmit a preamble for the random access procedure to the candidate cell, monitor a physical downlink control channel on at least one of the serving cell or the candidate cell, and receive a random access response from the at least one of the serving cell or the candidate cell.

[0005] In a second aspect, a terminal device is provided, the terminal device including a processor configured to: receive, from a serving cell, downlink control information including a value of a power ramping counter for a preamble, the downlink control information triggering a random access procedure on a candidate cell among a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility; determine a receive target power for the preamble based on the value of the power ramping counter; and transmit the preamble for the random access procedure to the candidate cell based on the receive target power.

[0006] In a third aspect, a terminal device is provided, the terminal device comprising a processor configured to cause the terminal device to receive, from a serving cell, first downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmit a preamble for the random access procedure to the candidate cell, and receive, from the serving cell, second downlink control information indicating whether the random access procedure has been completed successfully.

[0007] In a fourth aspect, there is provided a method of communication, the method including: receiving, in a terminal device, from a serving cell, downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmitting a preamble for the random access procedure to the candidate cell, performing monitoring of a physical downlink control channel on at least one of the serving cell or the candidate cell, and receiving a random access response from the at least one of the serving cell or the candidate cell.

[0008] In a fifth aspect, there is provided a method of communication, the method including: receiving, in a terminal device, from a serving cell downlink control information including a value of a power ramping counter for a preamble, the downlink control information triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, determining a receive target power for the preamble based on the value of the power ramping counter, and transmitting the preamble for the random access procedure to the candidate cell based on the receive target power.

[0009] In a sixth aspect, there is provided a method of communications, the method including: receiving, in a terminal device, from a serving cell, first downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmitting a preamble for the random access procedure to the candidate cell, and receiving, from the serving cell, second downlink control information indicating whether the random access procedure has been completed successfully.

[0010] In a seventh aspect, there is provided a computer-readable medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform a method according to any one of the fourth to sixth aspects of the present disclosure.

[0011] Other features of the present disclosure will be readily apparent from the following description. [Brief explanation of the drawings]

[0012] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description of several embodiments of the present disclosure in the accompanying drawings.

[0013] [Figure 1A] FIG. 1 illustrates an exemplary communication network in which some embodiments of the present disclosure may be implemented.

[0014] [Figure 1B] 1 is a schematic diagram illustrating network protocol layer entities that may be established for a User Plane (UP) protocol stack in an apparatus according to some embodiments of the present disclosure.

[0015] [Figure 1C] 1 is a schematic diagram illustrating network protocol layer entities that may be established for a control plane (CP) protocol stack in an apparatus according to some embodiments of the present disclosure.

[0016] [Figure 1D] 1 is a schematic diagram illustrating a Central Unit (CU) / Distributed Unit (DU) architecture in which some embodiments of the present disclosure can be implemented.

[0017] [Figure 1E] FIG. 1 is a schematic diagram illustrating a process of LTM in which some embodiments of the present disclosure can be implemented.

[0018] [Figure 2] FIG. 1 is a schematic diagram illustrating a communication process in an RA procedure for an LTM according to an embodiment of the present disclosure.

[0019] [Figure 3] FIG. 10 is a schematic diagram illustrating another communication process in an RA procedure for LTM according to an embodiment of the present disclosure.

[0020] [Figure 4] FIG. 10 is a schematic diagram illustrating yet another communication process in an RA procedure for LTM according to an embodiment of the present disclosure.

[0021] [Figure 5] FIG. 1 illustrates an exemplary communication method implemented in a terminal device, according to some embodiments of the present disclosure.

[0022] [Figure 6] FIG. 10 illustrates another exemplary communication method implemented in a terminal device, according to some embodiments of the present disclosure.

[0023] [Figure 7] FIG. 10 illustrates yet another exemplary communication method implemented in a terminal device, according to some embodiments of the present disclosure.

[0024] [Figure 8] FIG. 1 is a schematic block diagram of an apparatus suitable for implementing embodiments of the present disclosure.

[0025] In the drawings, the same or similar reference numbers represent the same or similar elements. DETAILED DESCRIPTION OF THE INVENTION

[0026] The principles of the present disclosure will now be described with reference to some embodiments. It should be understood that these embodiments are provided for illustrative purposes only to aid those skilled in the art in understanding and practicing the present disclosure, and do not imply any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways different from those described below.

[0027] 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.

[0028] As used herein, the term "terminal device" refers to any device with wireless or wired communication capabilities. Examples of terminal devices include User Equipment (UE), personal computers, desktops, mobile phones, cellular phones, smartphones, Personal Digital Assistants (PDAs), portable computers, tablets, wearable devices, Internet of Things (IoT) devices, Ultra-reliable and Low Latency Communication (URLLC) devices, Internet of Everything (IoE) devices, Machine Type Communication (MTC) devices, vehicle-mounted devices for V2X communications where X stands for pedestrian, vehicle, or infrastructure / network, devices for Integrated Access and Backhaul (IAB), satellite- or airborne vehicles in a Non-Terrestrial Network (NTN) including High Altitude Platforms (HAPs) including satellites and Unmanned Aircraft Systems (UASs), Augmented Reality (AR), Mixed Reality (MR), and other technologies. This includes, but is not limited to, extended reality (XR) devices that include different types of reality, such as real world reality (VR), virtual reality (VR), unmanned aerial vehicles (UAVs), which are aircraft without a human pilot and are commonly referred to as drones, devices on high speed trains (HST), image capture devices such as digital cameras, sensors, gaming devices, music storage and playback devices, or internet devices that enable wireless or wired internet access and browsing.The "terminal device" may further have "multicast / broadcast" capabilities to support public safety and mission-critical V2X applications, transparent IPv4 / IPv6 multicast distribution, IPTV, smart TV, wireless services, over-the-air software distribution, group communication, and IoT applications. It may also incorporate one or more Subscriber Identity Modules (SIMs), known as multi-SIMs. The term "terminal device" may be used interchangeably with UE, mobile station, subscriber station, mobile terminal, user terminal, or wireless device.

[0029] The term "network device" as used herein means a device capable of providing or hosting a cell or coverage area in which a terminal device can communicate. Examples of network devices include, but are not limited to, a Node B (Node B or NB), an evolved Node B (eNode B or eNB), a next generation Node B (gNB), a Transmission Reception Point (TRP), a Remote Radio Unit (RRU), a Radio Head (RH), a Remote Radio Head (RRH), an IAB node, a low-power node such as a femto node or a pico node, a Reconfigurable Intelligent Surface (RIS), etc.

[0030] A terminal device or a network device may have artificial intelligence (AI) or machine learning capabilities, which generally include a model trained from a large amount of data collected for a specific function and can be used to predict some information.

[0031] The terminal device or network device may operate on several frequency ranges, such as FR1 (410 MHz to 7125 MHz), FR2 (24.25 GHz to 71 GHz), frequency bands greater than 100 GHz, and Terahertz (THz). It can also operate on licensed, unlicensed, and shared spectrum. The terminal device may have two or more connections with the network device under a Multi-Radio Dual Connectivity (MR-DC) application scenario. The terminal device or network device can operate in full duplex, flexible duplex, and cross-division duplex modes.

[0032] Embodiments of the present disclosure may be implemented in test equipment, such as, for example, a signal generator, a signal analyzer, a spectrum analyzer, a network analyzer, a test terminal device, a test network device, a channel emulator, and the like.

[0033] In one embodiment, a terminal device may be connected to a first network device and a second network device. One of the first network device and the second network device may be a master node and the other may be a secondary node. The first network device and the second network device may use different radio access technologies (RATs). In one embodiment, the first network device may be a first RAT device, and the second network device may be a second RAT device. In one embodiment, the first RAT device is an eNB, and the second RAT device is a gNB. Information regarding the different RATs may be transmitted to the terminal device from at least one of the first network device or the second network device. In one embodiment, the first information may be transmitted from the first network device to the terminal device, and the second information may be transmitted from the second network device directly or via the first network device to the terminal device. In one embodiment, information regarding the terminal device configuration configured by the second network device may be transmitted from the second network device via the first network device. The information regarding the reconfiguration of the terminal device configured by the second network device may be transmitted to the terminal device directly from the second network device or via the first network device.

[0034] As used herein, the singular forms "a," "an," and "said" include the plural forms unless the context clearly indicates otherwise. The term "comprises" and variations thereof should be understood as open-ended terms meaning "including, but not limited to." The term "based on" should be understood as "based at least in part on." The terms "one embodiment" and "embodiment" should be understood as "at least one embodiment." The term "another embodiment" should be understood as "at least one other embodiment." Terms such as "first," "second," etc. may refer to different or the same object. The following may include other explicit and implicit definitions.

[0035] In some instances, values, procedures, or devices are referred to as "best," "lowest," "highest," "minimum," "maximum," etc. It should be understood that such descriptions are intended to illustrate that selections may be made from among many functional alternatives used, and that such selections are not necessarily better, smaller, higher, or otherwise more preferred than other selections.

[0036] In the context of this disclosure, the term "cell switch" may be used interchangeably with "reconfiguration with synchronization for a Secondary Cell Group (SCG) or Master Cell Group (MCG)" or "cell change." The term "PSCell" refers to an SpCell of an SCG, the term "PCell" refers to an SpCell of an MCG, and the term "SpCell" refers to a primary cell of an SCG or an MCG. The term "SCell" refers to a secondary cell. The term "lower layer signaling" may be used interchangeably with "L1 / L2 signaling." The term "RRC reconfiguration" may be used interchangeably with "RRC reconfiguration message."

[0037] To reduce the interruption time for LTM, it is agreed that an RA procedure may be performed to acquire TA of a candidate cell before a cell switch command is received. Conventionally, the RA procedure is always performed on the serving cell of the UE. In that case, the conventional RA procedure is no longer suitable for acquiring TA of a candidate cell that is not the serving cell of the UE.

[0038] In view of this, embodiments of the present disclosure provide a communication solution to overcome the above problems and other potential problems. In one aspect, a terminal device receives downlink control information (DCI) from a serving cell, triggering an RA procedure on a candidate cell among a set of candidate cells that allow LTM. Upon receiving the DCI, the terminal device transmits a preamble for the RA procedure to the candidate cell and performs physical downlink control channel (PDCCH) monitoring on at least one of the serving cell or the candidate cell. The terminal device receives a random access response (RAR) from at least one of the serving cell or the candidate cell. In this manner, RAR reception for a PDCCH-ordered RA for the LTM candidate cell may be defined.

[0039] In another aspect, a terminal device receives from a serving cell a DCI including a value of a power ramping counter for a preamble, the DCI triggering an RA procedure on a candidate cell among a set of candidate cells that allow LTM. The terminal device determines a reception target power for the preamble based on the value of the power ramping counter, and transmits a preamble for the RA procedure to the candidate cell based on the reception target power. In this way, preamble transmission for RA commanded on the PDCCH for the LTM candidate cell may be properly realized without RAR.

[0040] In yet another aspect, the terminal device receives, from a serving cell, a first DCI that triggers an RA procedure on a candidate cell among a set of candidate cells that allow LTM. The terminal device transmits a preamble for the RA procedure to the candidate cell and receives, from the serving cell, a second DCI that indicates whether the RA procedure has been completed successfully. In this manner, an RA procedure for an RA commanded on a PDCCH for an LTM candidate cell may also be defined.

[0041] The principles and implementation aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. Example of a communication network

[0042] 1A is a schematic diagram illustrating an exemplary communication network 100A in which some embodiments of the present disclosure can be implemented. As shown in FIG. 1A, communication network 100A may include a terminal device 110 and multiple network devices 120 and 130 (also referred to herein as network device 120 and network device 130 for convenience). Network devices 120 and 130 provide respective cells 121 and 131 to serve the terminal device.

[0043] 1A is provided for illustrative purposes and should not be construed as implying any limitations on the present disclosure. Communication network 100A may include any suitable number of network devices and / or terminal devices suitable for carrying out implementations of the present disclosure. Furthermore, each of network devices 120 and 130 may provide more cells to terminal device 110.

[0044] 1A, terminal device 110 may communicate with network device 120 or 130 via a channel, such as a wireless communication channel. Communications in communication network 100A may conform to any suitable standard, including, but not limited to, Global System for Mobile Communications (GSM), Long Term Evolution (LTE), LTE-Evolution, LTE-Advanced (LTE-A), New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE Radio Access Network (GERAN), Machine Type Communication (MTC), etc. Embodiments of the present disclosure may be performed in accordance with any generation of communication protocols now known or developed in the future. Examples of communication protocols include, but are not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) communication protocols, 5.5G, 5G-Advanced networks, or sixth generation (6G) networks.

[0045] Communication in the direction from terminal device 110 to network device 120 or 130 is referred to as uplink (UL) communication, and communication in the reverse direction from network device 120 or 130 to terminal device 110 is referred to as downlink (DL) communication. Terminal device 110 may travel between cells of network devices 120, 130, and possibly other network devices. In UL communication, terminal device 110 may transmit UL data and control information to network device 120 or 130 over a UL channel. In DL communication, network device 120 or 130 may transmit DL data and control information to terminal device 110 over a DL channel.

[0046] Communications in the communication network 100A may be performed according to UP and CP protocol stacks. Generally speaking, for a communication device (e.g., a terminal device or a network device), there may be multiple entities at multiple network protocol layers in the protocol stack, and these entities may be configured to perform corresponding processes on data or signaling transmitted from and received by the communication device. FIG. 1B shows a schematic diagram 100B illustrating network protocol layer entities that may be established for the UP protocol stack in a device according to some embodiments of the present disclosure. For convenience, the following description will be given using communication between the terminal device 110 and the network device 120 as an example. It should be understood that the following description is also applicable to communication between the terminal device 110 and the network device 130.

[0047] In some embodiments, network devices 120 and 130 may be different network devices. In some embodiments, network devices 120 and 130 may be the same network device.

[0048] 1B , in the UP, each of the terminal device 110 and the network device 120 may include an L1 layer entity, i.e., a physical (PHY) layer entity (also referred to as a PHY entity), and one or more entities of higher layers (L2 and Layer 3 (L3) layers, or higher layers), including a medium access control (MAC) layer entity (also referred to as a MAC entity), a radio link control (RLC) layer entity (also referred to as an RLC entity), a packet data convergence protocol (PDCP) layer entity (also referred to as a PDCP entity), and a service data application protocol (SDAP) layer entity (also referred to as an SDAP entity, which will be established in 5G and subsequent generation networks). In some cases, the PHY, MAC, RLC, PDCP, and SDAP entities have a stack structure.

[0049] FIG. 1C illustrates a schematic diagram 100C illustrating network protocol layer entities that can be established for a CP protocol stack in an apparatus according to some embodiments of the present disclosure. As illustrated in FIG. 1C, in a CP, each of the terminal device 110 and the network device 120 may include one or more entities of higher layers (L2 and L3 layers), including an L1 layer entity, i.e., a PHY layer entity (also referred to as a PHY entity), a MAC layer entity (also referred to as a MAC entity), an RLC layer entity (also referred to as an RLC entity), a PDCP layer entity (also referred to as a PDCP entity), and a Radio Resource Control (RRC) layer entity (also referred to as an RRC entity). The RRC layer may also be referred to as an Access Stratum (AS) layer, and thus, the RRC entity may also be referred to as an AS entity. As illustrated in FIG. 1C, the terminal device 110 may also include a Non-Access Stratum (NAS) layer entity (also referred to as a NAS entity). The NAS layer on the network side is located not in a network device but in a core network (CN, not shown). In some cases, these entities have a stack structure.

[0050] In the context of this disclosure, L1 refers to the PHY layer, L2 refers to the MAC or RLC or PDCP or SDAP layer, and L3 refers to the RRC layer. In the context of this disclosure, L1 or L2 may collectively be referred to as a lower layer, and L3 may be referred to as an upper layer. Therefore, L1 or L2 signaling may be referred to as lower layer signaling, and L3 signaling may be referred to as upper layer signaling.

[0051] Generally, communication channels are divided into logical channels, transmission channels, and physical channels. Physical channels are channels through which the PHY layer actually transmits information. For example, physical channels may include a Physical Uplink Control Channel (PUCCH), a Physical Uplink Shared Channel (PUSCH), a Physical Random-Access Channel (PRACH), a PDCCH, a Physical Downlink Shared Channel (PDSCH), and a Physical Broadcast Channel (PBCH).

[0052] The transmission channel is a channel between the PHY layer and the MAC layer, and may include, for example, a Broadcast Channel (BCH), a Downlink Shared Channel (DL-SCH), a Paging Channel (PCH), an Uplink Shared Channel (UL-SCH), and a Random Access Channel (RACH).

[0053] Logical channels are channels between the MAC layer and the RLC layer. For example, logical channels may include a dedicated control channel (DCCH), a common control channel (CCCH), a paging control channel (PCCH), a broadcast control channel (BCCH), and a dedicated traffic channel (DTCH).

[0054] Generally, a channel between the RRC layer and the PDCP layer is called a radio bearer. The terminal device 110 may be configured with at least one data radio bearer (DRB) for carrying data plane data and at least one signaling radio bearer (SRB) for carrying control plane data. Four types of SRBs, SRB0, SRB1, SRB2, and SRB3, may be defined in the RRC layer. SRB0 uses the CCCH for establishing or re-establishing an RRC connection. SRB1 uses the DCCH and is established when an RRC connection is established. SRB2 uses the DCCH and is established during RRC re-establishment and after initial security activation. SRB3 uses the DCCH and is established between the terminal device 110 and the SN when a dual connection is established.

[0055] 1D shows a schematic diagram 100D illustrating a CU / DU architecture in which some embodiments of the present disclosure can be implemented. The CU / DU architecture may be established in a network device.

[0056] In the context of this disclosure, a CU (also referred to herein as a gNB-CU) is a logical node that hosts the RRC, SDAP, and PDCP protocols of a gNB or the RRC and PDCP protocols of an en-gNB, and controls the operation of one or more DUs (also referred to herein as a gNB-DU). The gNB-CU terminates an F1 interface connected to a gNB-DU. A DU is a logical node that hosts the RLC, MAC, and PHY layers of a gNB or an en-gNB, and its operation is partially controlled by the gNB-CU. One gNB-DU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates an F1 interface connected to a gNB-CU.

[0057] As shown in FIG. 1D , CU 141 is shown. It should be understood that more CUs may be included. CU 141 may communicate with multiple DUs. Here, for illustration purposes, two DUs 151 and 152 are shown. It should be understood that more DUs may be provided to implement the embodiments of the present disclosure. Although not shown, CU 141 may be responsible for achieving the functions of an SDAP entity and a PDCP entity, and DU 151 or 152 may be responsible for achieving the functions of an RLC entity, a MAC entity, and a PHY entity.

[0058] DU 151 may serve cells 161, 162, and 163. DU 152 may serve cells 164, 165, and 166. It should be understood that this is just one example and any more or fewer cells are possible. Terminal device 110 may communicate with any of these cells.

[0059] In some embodiments, the terminal device 110 may switch from one cell to another cell under the control of the same CU and the same DU. For example, the terminal device 110 may be handed over from one cell 161 to another cell 162. This is referred to as an intra-CU, intra-DU serving cell switch. In some embodiments, the terminal device 110 may switch from one cell to another cell under the control of the same CU and a different DU. For example, the terminal device 110 may be handed over from one cell 161 to another cell 164. In this case, a cell switch occurs from one cell of DU 151 to another cell of DU 152. This is referred to as an intra-CU, inter-DU serving cell switch. In another example, the terminal device 110 may be handed over from a cell of one DU to a cell of another DU under the control of a different CU. In this case, a handover occurs from a CU to another CU. This is referred to as an inter-CU handover.

[0060] Network device 120 and network device 130 may correspond to one or two DUs under the same CU. In some embodiments, the CU and DU may be implemented in separate devices. In some embodiments, the CU and DU may be implemented in the same device. In some embodiments, different DUs may be implemented in separate devices.

[0061] 1A , in some embodiments, terminal device 110 may be located within the coverage of cell 121 of network device 120, and terminal device 110 may communicate with network device 120 based on a network configuration. In this case, cell 121 may be referred to as a serving cell of terminal device 110.

[0062] In some embodiments, terminal device 110 may establish a dual connection (i.e., a simultaneous connection) with network device 120 and another network device (not shown). In some embodiments, network device 120 may serve as a master node (MN). In these embodiments, terminal device 110 may communicate with network device 120 via a set of serving cells. The set of serving cells constitutes an MCG, and a primary cell within the MCG is referred to as a PCell. In some scenarios, the PCell may change from cell 121 to cell 131, which is referred to as a handover. In some embodiments, network device 120 may serve as a secondary node (SN). In these embodiments, the set of serving cells provided by network device 120 constitutes an SCG, and a primary cell within the SCG is referred to as a PSCell. In some scenarios, the PSCell may change from cell 121 to cell 131, which is referred to as a PScell ​​change.

[0063] In some scenarios, the network device 120 may receive an L1 measurement report from the terminal device 110. Based on the L1 measurement report, the network device 120 may change the serving cell of the terminal device 110 via the MAC CE. This procedure is referred to as LTM. The network device 120 may prepare one or more candidate cells and provide the candidate cell configurations to the terminal device 110 via an RRC message. The network device 120 then triggers an LTM cell switch by selecting one of the candidate cell configurations as a target configuration for LTM.

[0064] FIG. 1E is a schematic diagram illustrating a process 100E of LTM capable of implementing some embodiments of the present disclosure. For illustrative purposes, process 100E will be described with reference to FIG. 1A. Process 100E may involve terminal device 110 and network device 120 as shown in FIG. 1A. Network device 120 may be an MN or SN that serves terminal device 110. In this example, network device 120 provides a serving cell for terminal device 110. Network device 130, which provides one or more candidate cells to terminal device 110, is the same network device as network device 120.

[0065] 1E, in the LTM preparation phase, the terminal device 110 may send a Measurement Report message to the network device 120 (170). The network device 120 may decide to use LTM (171) and start LTM candidate preparation. The network device 120 may send an RRC Reconfiguration message including configuration of one or more LTM candidate target cells to the terminal device 110 (172). The terminal device 110 may store the configuration of the LTM candidate target cells and send an RRC Reconfiguration Complete message to the network device 120 (173).

[0066] During the initial synchronization phase, the terminal device 110 may perform DL synchronization and TA acquisition with the candidate target cell before receiving the LTM cell switch command (174).

[0067] In the LTM execution phase, the terminal device 110 may perform L1 measurements on the configured LTM candidate target cell and send a lower layer measurement report to the network device 120 (175). The network device 120 may decide to perform an LTM cell switch to the target cell (176) and send a MAC CE triggering the LTM cell switch by including the candidate configuration index of the target cell (177). The terminal device 110 may switch to the configuration of the LTM candidate target cell (178). If a TA is unavailable, the terminal device 110 may perform a random access procedure to the target cell (179). The terminal device 110 indicates successful completion of the LTM cell switch to the target cell (180).

[0068] In the LTM completion phase, the terminal device 110 may indicate successful completion of the LTM cell switch to the target cell (180).

[0069] It can be seen that an RA procedure may be performed to acquire the TA of the candidate cell before the cell switch command is received, thus reducing the interruption time for LTM. However, the conventional RA procedure is always performed on the UE's serving cell, making it unsuitable for acquiring the TA of the candidate cell.

[0070] The embodiments of the present disclosure provide a communication solution for RA to candidate cells, which will be described in detail with reference to Figures 2 to 4.

[0071] Example of RA implementation for candidate cells 2 is a schematic diagram illustrating a communication process 200 in an RA procedure for LTM according to an embodiment of the present disclosure. For illustrative purposes, process 200 will be described with reference to FIG. 1A. Process 200 may involve terminal device 110 and network device 120 as shown in FIG. 1A. In this example, network device 120 provides a serving cell (e.g., cell 121) to terminal device 110, and network device 130 provides a candidate cell (e.g., cell 131) to terminal device 110.

[0072] As shown in FIG. 2, network device 120 may send 205 an RRC reconfiguration message to terminal device 110 that includes a set of RRC configurations corresponding to a set of candidate cells that allow LTM.

[0073] Terminal device 110 may receive 210 DCI / PDCCH signaling from a serving cell (e.g., cell 121) of network device 120 to trigger an RA procedure on a candidate cell (e.g., cell 131) of a set of candidate cells. This serving cell may be an SpCell, PCell, or PSCell of network device 120. This RA procedure is also referred to as a PDCCH-commanded RA procedure. Upon receiving the DCI, terminal device 110 may transmit 220 a preamble for the RA procedure to the candidate cell of network device 130.

[0074] Terminal device 110 may perform PDCCH monitoring on at least one of the serving cell or candidate cells 230. In some embodiments, upon transmitting the preamble, terminal device 110 may start a time window for RAR and monitor the PDCCH of at least one of the serving cell or candidate cells for RAR within the time window.

[0075] The terminal device 110 may then receive an RAR from the at least one of the serving cell or the candidate cell (240). For illustrative purposes, several exemplary embodiments of RAR reception are described below with reference to embodiments 1 to 4. Embodiment 1

[0076] In some embodiments, the RAR may include a TA command for the candidate cell.

[0077] In some embodiments where the RAR is received from the serving cell, the terminal device 110 may transmit a preamble on an RA resource (e.g., a preamble index or RA opportunity) dedicated to the candidate cell. In some embodiments where the RAR is received from the serving cell, the network device 120 may configure a dedicated search space for TA acquisition of the candidate cell, and the terminal device 110 may monitor the PDCCH in the configured search space. In some embodiments where the RAR is received from the serving cell, the RAR may include information about the candidate cell. For example, the RAR may include the ID of the candidate cell.

[0078] For illustrative purposes, an exemplary procedure may be described as follows. The UE receives PDCCH signaling / DCI from the serving cell (e.g., SpCell, PCell, PSCell) that triggers an RA procedure (i.e., RA commanded on PDCCH) on the LTM candidate cell, and transmits a preamble to the candidate cell. When the Random Access Response is transmitted, the UE should: - Start a ra-ResponseWindow and, while the ra-ResponseWindow is running, monitor the PDCCH of at least one of the candidate or serving cells for a random access response identified by the RA-RNTI. - receiving a random access response from at least one of the candidate cells or the serving cell; - if PDCCH monitoring and RAR reception are performed in the serving cell, A dedicated RA resource (e.g., a preamble index) may be configured for random access in the candidate cell for early TA acquisition; A dedicated separate search space may be configured for random access in candidate cells for early TA acquisition; The RAR may include information of the candidate cell, for example, a cell ID.

[0079] In some embodiments, the candidate cell may belong to a Timing Advance Group (TAG). In these embodiments, the terminal device 110 may apply a TA command for the TAG. In some embodiments, the terminal device 110 may start or restart a timer for time alignment associated with the TAG. In some embodiments, the RA procedure on the candidate cell is a contention-based RA procedure. If contention resolution is deemed unsuccessful, the terminal device 110 may stop the timer for time alignment associated with the TAG. In these embodiments, if the timer expires, the terminal device 110 may maintain the TA between the uplink and downlink of the TAG. In some embodiments, if the timer expires, the terminal device 110 may discard the TA between the uplink and downlink of the TAG.

[0080] In some embodiments, terminal device 110 may receive a TA command MAC CE for this TAG from network device 120, apply the TA command for the TAG, and restart the timer for time alignment associated with the TAG.

[0081] In some embodiments, terminal device 110 may receive a MAC CE indicating a cell switch to the candidate cell from network device 120. Based on the MAC CE, terminal device 110 may set the TAG as the terminal device's 110 Primary Timing Advance Group (PTAG).

[0082] For illustrative purposes, an exemplary procedure may be described as follows. If a TA command is received in a RAR message for a candidate cell that belongs to a TAG (e.g., which may be named as a Candidate TAG (CTAG)), For Contention-Free Random Access (CFRA), the terminal device 110 may apply a TA command for the TAG and start or restart a timeAlignmentTimer associated with the TAG; For Contention-Based Random Access (CBRA), terminal device 110 may apply a TA command for the TAG and start or restart the timeAlignmentTimer associated with the TAG. If contention resolution is deemed unsuccessful, terminal device 110 may stop the timeAlignmentTimer associated with the TAG. When the timeAlignmentTimer associated with the TAG to which the candidate cell belongs expires, the terminal device 110 TA may be kept or discarded, where N TA represents the TA between DL and UL. When a TA command MAC CE is received for a TAG, the N TA may be maintained, and terminal device 110 may apply the TA command for TAG and restart timeAlignmentTimer. Upon receiving a MAC CE that triggers an LTM to a candidate cell, the TAG becomes the PTAG of the terminal device 110.

[0083] In this way, RAR reception for RA commanded in PDCCH for TA acquisition of LTM candidate cells can be realized. Embodiment 2

[0084] Currently, in the case of CFRA, the UL grant is included in the RAR and the UE needs to perform further UL transmissions although the RA has already been successfully completed. However, if the RA procedure for TA acquisition of the candidate cell is a contention-free procedure, after receiving the RAR, it is difficult to perform further UL transmissions to the network, especially to the candidate cell, because the candidate cell is not yet the serving cell of the UE.

[0085] In light of this, embodiments of the present disclosure provide a solution for CFRA to solve these and other potential problems.

[0086] In some embodiments, if the RAR includes a MAC sub-protocol data unit (PDU) having a Random Access Preamble identifier (RAPID) corresponding to the transmitted preamble index, the terminal device 110 may consider the RAR reception to be successful.

[0087] In some embodiments, the RAR may include a MAC sub-PDU, which is a MAC sub-header with only RAPID. Upon receiving the RAR, the terminal device 110 may determine that the RA procedure has been completed successfully. In other words, the MAC sub-header with only RAPID may be used as a response. In these embodiments, the TA value may be transmitted in the MAC CE to trigger a cell switch.

[0088] In some embodiments, the RAR may not include an uplink grant. Upon receiving the RAR, the terminal device 110 may determine that the RA procedure has been completed successfully. In other words, a new RAR format that does not include an UL grant may be used. In some embodiments, the RAR received by the terminal device 110 may include a TA value but may not include at least one of a Temporary Cell Radio Network Temporary Identity (T-CRNTI) or an UL grant. Upon receiving this type of RAR, the terminal device 110 may consider the RA procedure to have been completed successfully.

[0089] In some embodiments, terminal device 110 may determine that the RA procedure has completed successfully and may ignore the UL grant in the RAR. In other words, terminal device 110 may ignore the received UL grant in the RAR or may not process or indicate the received UL grant value to lower layers (e.g., the PHY layer) and may consider the RA procedure to have completed successfully.

[0090] This way, no further UL transmissions need to be performed to the network, especially for candidate cells. Embodiment 3

[0091] If the RA procedure for TA acquisition of one candidate cell is a contention-based procedure, the current contention resolution mechanism is no longer suitable, for example, it is not valid to send a Cell Radio Network Temporary Identity (C-RNTI) MAC CE containing the C-RNTI of the MAC entity, since the C-RNTI of the MAC entity is not the identity (ID) of the UE in the candidate cell.

[0092] In light of this, embodiments of the present disclosure provide a solution for CBRA to solve these and other potential problems.

[0093] 2, if the RAR is successfully received, terminal device 110 may transmit a message (e.g., Msg3) including the ID of terminal device 110 to a candidate cell of network device 130 using the UL grant scheduled in the RAR (250). In other words, if the RAR includes a MAC sub-PDU having a random access preamble identifier corresponding to the transmitted preamble index, terminal device 110 may consider the RAR reception successful. Terminal device 110 may then transmit the ID of terminal device 110 in Msg3. In some embodiments, terminal device 110 may avoid transmitting any other MAC CEs and data from any logical channels in Msg3.

[0094] In some embodiments, the ID of terminal device 110 may be a Radio Network Temporary Identity (RNTI) of terminal device 110 associated with the candidate cell. For example, the ID of terminal device 110 may be a C-RNTI of terminal device 110 associated with the candidate cell. It should be understood that the ID of terminal device 110 may take any other suitable form.

[0095] In some embodiments, the RNTI of the terminal device 110 associated with the candidate cell may be configured by the network device 120 using an RRC message, for example, within a reconfigurationWithSync IE of a cell group configuration associated with the candidate cell.

[0096] In some embodiments, the ID of terminal device 110 may be carried in a MAC CE (also referred to herein as the first MAC CE for convenience). The first MAC CE may be transmitted in Msg3. In some embodiments, the first MAC CE may be a MAC CE dedicated for early TA acquisition. In some embodiments, the first MAC CE may be a C-RNTI MAC CE.

[0097] In some embodiments, the RRC layer of terminal device 110 may indicate to the MAC layer of terminal device 110 the RNTI of terminal device 110 associated with the candidate cell.

[0098] For illustrative purposes, an exemplary procedure may be described as follows. If this is the first successfully received random access response in this random access procedure, the UE should perform the following operations: indicating to the multiplexing and assembly entity in a subsequent uplink transmission to include a first MAC CE consisting of the identity of the UE associated with the candidate cell; Indicating to the multiplexing and assembly entity not to include data / MAC SDUs from other MAC CEs or any logical channels in subsequent uplink transmissions; It gets the MAC PDU to be transmitted from the multiplexing and assembly entity and stores it in the Msg3 buffer.

[0099] Continuing to refer to FIG. 2, after transmitting Msg3, the terminal device 110 may start a timer for contention resolution (e.g., ra-ContentionResolutionTimer) and monitor the PDCCH of the candidate cell while the timer is running (260).

[0100] In some embodiments, terminal device 110 may monitor PDCCH transmissions of a candidate cell identified by the RNTI of terminal device 110 associated with the candidate cell while the timer for contention resolution is running. Terminal device 110 may receive a PDCCH transmission from a candidate cell of network device 130 addressed to the RNTI of terminal device 110 associated with the candidate cell (270), and terminal device 110 may then determine that contention resolution is successful (280). In some embodiments, terminal device 110 may stop the timer for contention resolution. In some embodiments, terminal device 110 may discard a Temporary Cell Radio Network Temporary Identity (T-CRNTI) of terminal device 110. In some embodiments, terminal device 110 may determine that the random access procedure has completed successfully.

[0101] For example, the terminal device 110 may monitor a PDCCH transmission of a candidate cell identified by the RNTI of the terminal device 110 associated with the candidate cell while the timer is running. If notification of the reception of a PDCCH transmission of the candidate cell is received from a lower layer, and if the PDCCH transmission is addressed to the RNTI of the terminal device 110 associated with the candidate cell, the terminal device 110 may: consider this conflict resolution successful, Stopping the ra-ContentionResolutionTimer, Revoking the T-CRNTI, or and considering the random access procedure to have been successfully completed.

[0102] In some alternative embodiments, terminal device 110 may monitor the PDCCH of the candidate cell identified by the T-CRNTI while the contention resolution timer is running. Terminal device 110 may receive a PDCCH transmission from a candidate cell of network device 130 addressed to terminal device 110's T-CRNTI (270'). If the MAC PDU is successfully decoded, terminal device 110 may stop the contention resolution timer. If the MAC PDU includes a MAC CE (also referred to herein as a second MAC CE for convenience) that matches the contents in a message (e.g., Msg3), terminal device 110 may determine that contention resolution is successful (280'). For example, terminal device 110 may determine that contention resolution is successful if the MAC PDU includes a second MAC CE that matches the first MAC CE in Msg3. In some embodiments, terminal device 110 may discard its T-CRNTI and determine that the RA procedure completed successfully. In some embodiments, if the MAC CE does not include a second MAC CE that matches the contents in the message, terminal device 110 may discard the T-CRNTI, consider this contention resolution unsuccessful, and discard the successfully decoded MAC PDU.

[0103] For example, while the timer for contention resolution is running, the terminal device 110 may monitor PDCCH transmissions of a candidate cell identified by the T-CRNTI of the terminal device 110. If notification of reception of a PDCCH transmission of a candidate cell is received from a lower layer, and if the PDCCH transmission is addressed to the T-CRNTI of the terminal device 110 and the MAC PDU is successfully decoded, the terminal device 110 may stop the timer for contention resolution. If the MAC PDU includes a second MAC CE, and if the second MAC CE matches the content transmitted in Msg3 (e.g., the first MAC CE), the terminal device 110: consider this conflict resolution successful, Revoking the T-CRNTI, or and considering the random access procedure to have been successfully completed. Otherwise (i.e., if the MAC PDU does not contain the second MAC CE or if the second MAC CE does not match the content transmitted in Msg3 (e.g., the first MAC CE)), the terminal device 110: Revoking the T-CRNTI, or determining that the contention resolution was not successful and discarding the successfully decoded MAC PDU. Embodiment 4

[0104] While the ra-ResponseWindow is active, the terminal device 110 monitors PDCCH transmissions of a candidate cell of the network device 130 identified by the RNTI of the terminal device 110 associated with the candidate cell. In some embodiments, the monitoring of PDCCH transmissions may be performed in a dedicated search space configured by the network device 130 for contention-free early TA acquisition. In some embodiments, the terminal device 110 may receive a PDCCH transmission from the candidate cell of the network device 130 addressed to the RNTI of the terminal device 110 associated with the candidate cell (270''). In some embodiments, the terminal device 110 may consider the RAR to be successfully received. In some embodiments, the RNTI of the terminal device 110 associated with the candidate cell may be the C-RNTI of the terminal device 110 associated with the candidate cell.

[0105] In some embodiments, if a PDCCH transmission is received, terminal device 110 may determine that the RA procedure has completed successfully (280'').

[0106] For illustrative purposes, an exemplary procedure may be described as follows. When a contention-free random access preamble is transmitted on a candidate cell, the UE starts the ra-ResponseWindow and, while the ra-ResponseWindow is running, monitors the PDCCH transmissions of the candidate cell identified by the RNTI of the terminal device 110 associated with the candidate cell. The monitoring of the PDCCH transmissions may be performed in a search space dedicated for contention-free early TA acquisition. If the PDCCH transmission is addressed to the RNTI of the terminal device 110 associated with the candidate cell, the terminal device 110 may consider the random access procedure to have completed successfully.

[0107] The process 200 may define RAR reception for RAs commanded on the PDCCH for LTM candidate cells. Example of implementation of preamble transmission for candidate cells

[0108] In the absence of an RAR for TA acquisition of a candidate cell, there is no explicit indication of whether the RA procedure was completed successfully. If the RA procedure is not successful, it is unclear how to perform subsequent RA attempts, and in particular, how to perform power ramping for the second RA attempt.

[0109] In view of this, embodiments of the present disclosure provide a preamble transmission solution, which is described below in connection with FIG.

[0110] 3 is a schematic diagram illustrating another communication process 300 in an RA procedure for LTM according to an embodiment of the present disclosure. For illustrative purposes, process 300 will be described with reference to FIG. 1A. Process 300 may involve terminal device 110 and network device 120 as shown in FIG. 1A. In this example, network device 120 provides a serving cell (e.g., cell 121) to terminal device 110, and network device 130 provides a candidate cell (e.g., cell 131) to terminal device 110. The serving cell may be an SPCell, PCell, or PSCell of terminal device 110.

[0111] As shown in FIG. 3, the network device 120 may send 305 an RRC reconfiguration message to the terminal device 110 that includes a set of RRC configurations corresponding to a set of candidate cells that allow LTM.

[0112] Network device 120 may send 310 DCI / PDCCH signaling to terminal device 110 that triggers an RA procedure on a candidate cell (e.g., cell 131) in the set of candidate cells. The DCI / PDCCH signaling includes the value of the power ramping counter for the preamble (i.e., the value of the preamble power ramping counter).

[0113] 3, terminal device 110 may determine a reception target power for the preamble (i.e., a preamble reception target power) based on the value of the preamble power ramping counter (320). It should be understood that the preamble reception target power may be determined in any suitable manner, and the present disclosure is not limited in this respect.

[0114] Based on the preamble reception target power, the terminal device may transmit a preamble for the RA procedure to the network device 130 (330).

[0115] For illustrative purposes, an exemplary procedure may be described as follows. The UE receives PDCCH signaling / DCI triggering an RA on a candidate cell, and the value of PREAMBLE_POWER_RAMPING_COUNTER is signaled in the PDCCH / DCI. The UE determines the PREAMBLE_RECEIVED_TARGET_POWER for the RA preamble transmission based on the value of PREAMBLE_POWER_RAMPING_COUNTER received from the PDCCH / DCI.

[0116] By the process 300, preamble transmission for RA commanded on the PDCCH for the LTM candidate cell can be properly realized without RAR. Example of implementation of preamble transmission for candidate cells

[0117] Embodiments of the present disclosure provide a solution for an RA procedure without an RAR, which is described below in connection with FIG.

[0118] 4 is a schematic diagram illustrating yet another communication process 400 in an RA procedure for LTM according to an embodiment of the present disclosure. For illustrative purposes, process 400 will be described with reference to FIG. 1A. Process 400 may involve terminal device 110 and network device 120 as shown in FIG. 1A. In this example, network device 120 provides a serving cell (e.g., cell 121) to terminal device 110, and network device 130 provides a candidate cell (e.g., cell 131) to terminal device 110. The serving cell may be an SPCell, PCell, or PSCell of terminal device 110.

[0119] As shown in FIG. 4, the network device 120 may send 405 an RRC reconfiguration message to the terminal device 110 that includes a set of RRC configurations corresponding to a set of candidate cells that allow LTM.

[0120] The serving cell of the network device 120 may transmit (410) to the terminal device 110 a DCI (also referred to herein as a first DCI for convenience) that triggers an RA procedure on a candidate cell (e.g., cell 131) from the set of candidate cells.

[0121] Referring to FIG. 4, terminal device 110 may transmit a preamble for the RA procedure to a candidate cell in network device 130 (420).

[0122] Terminal device 110 may receive 430 from network device 120 a DCI (also referred to herein as a second DCI for convenience) indicating whether the RA procedure was completed successfully.

[0123] In some embodiments, upon receiving the first DCI, the terminal device 110 may start a timer and, while the timer is running, monitor the PDCCH of the serving cell of the network device 120 for the second DCI. For example, the UE receives PDCCH signaling / DCI triggering an RA on a candidate cell, sets a preamble power ramping counter to 1 during initialization of the random access procedure, performs a preamble transmission, starts a timer, and, while the timer is running, monitors the PDCCH of the SpCell for a random access response identified by the RA-RNTI. In some embodiments, the timer may be an RAR window (e.g., ra-ResponseWindow). It should be understood that any other suitable method is also possible. In some embodiments, upon receiving the second DCI, the terminal device 110 may stop the timer.

[0124] In some embodiments, if the timer expires, terminal device 110 may determine that the RA procedure completed successfully. In some alternative embodiments, if the timer expires, terminal device 110 may determine that the RA procedure did not complete successfully.

[0125] Continuing to refer to FIG. 4, in some embodiments, if the RA procedure is not completed successfully, terminal device 110 may perform an RA resource selection procedure in which a power ramping counter for the preamble is increased (440).

[0126] For example, if the second PDCCH signaling / DCI indicates that the RA procedure was not completed successfully, the UE performs a random access resource selection procedure, during which the preamble power ramping counter is increased by 1. If the second PDCCH signaling / DCI indicates that the RA procedure was completed successfully, the terminal device 110 may determine that the RA procedure was completed successfully.

[0127] The process 400 may define an RA procedure for PDCCH-commanded RA for an LTM candidate cell. Example implementation of the method

[0128] Therefore, embodiments of the present disclosure provide communication methods implemented in a terminal device, which are described below with reference to Figures 5 to 7.

[0129] 5 illustrates an exemplary communication method 500 implemented in a terminal device, according to some embodiments of the present disclosure. For example, method 500 may be performed in terminal device 110 as shown in FIG. 1A. For purposes of explanation, method 500 will be described below with reference to FIG. 1A. It should be understood that method 500 may include additional blocks not shown and / or omit some blocks that are shown, and that the scope of the present disclosure is not limited in this respect.

[0130] In block 510, terminal device 110 receives DCI from a serving cell (eg, cell 121) that triggers an RA procedure on a candidate cell (eg, cell 131) of a set of candidate cells that allow LTM.

[0131] In block 520, terminal device 110 transmits a preamble for the RA procedure to the candidate cell. In block 530, terminal device 110 performs PDCCH monitoring on at least one of the serving cell or the candidate cell.

[0132] Terminal device 110 receives an RAR from the at least one of the serving cell or the candidate cell at block 540. In some embodiments, the RAR may include a TA command for the candidate cell.

[0133] In some embodiments in which terminal device 110 receives an RAR from a serving cell, terminal device 110 may transmit a preamble on an RA resource dedicated to the candidate cell. Alternatively or additionally, terminal device 110 may perform PDCCH monitoring based on a search space dedicated to the candidate cell. In some embodiments, the RAR may include information about the candidate cell.

[0134] In some embodiments, where the candidate cell belongs to a TAG, the terminal device 110 may apply a TA command for that TAG. In some embodiments, the terminal device 110 may start or restart a timer for time alignment associated with the TAG. When the timer expires, the terminal device 110 may maintain the TA value of the TAG. In some embodiments, the terminal device 110 may receive a MAC CE from the serving cell indicating a cell switch to the candidate cell and set the TAG as the terminal device 110's PTAG.

[0135] In some embodiments, if the RAR includes a MAC sub-PDU and the MAC sub-PDU is a MAC sub-header with only RAPID, terminal device 110 may determine that the RA procedure has completed successfully. In some embodiments, if the RAR does not include an uplink grant, terminal device 110 may determine that the RA procedure has completed successfully. In some embodiments, if the RAR includes an uplink grant, terminal device 110 may determine that the RA procedure has completed successfully and ignore the uplink grant.

[0136] In some embodiments, if the RAR is successfully received, the terminal device 110 may use the uplink grant scheduled in the RAR to transmit a message including the ID of the terminal device 110 to the candidate cell. In some embodiments, the ID of the terminal device 110 may be the RNTI of the terminal device 110 associated with the candidate cell. In some embodiments, the ID of the terminal device 110 may be carried in the first MAC CE.

[0137] In some embodiments, terminal device 110 may start a contention resolution timer and monitor the PDCCH of the candidate cell while the timer is running. In some embodiments, terminal device 110 may receive a PDCCH transmission from the candidate cell addressed to the RNTI of terminal device 110 associated with the candidate cell and determine that contention resolution is successful. In some embodiments, terminal device 110 may stop the contention resolution timer, discard the T-CRNTI of terminal device 110, and determine that the RA procedure has completed successfully.

[0138] In some embodiments, terminal device 110 may receive a PDCCH transmission from a candidate cell addressed to terminal device 110's T-CRNTI. If the MAC PDU is successfully decoded, terminal device 110 may stop the timer for contention resolution. If the MAC PDU includes a second MAC CE that matches the contents in the message, terminal device 110 may determine that contention resolution was successful. In some embodiments, terminal device 110 may discard terminal device 110's T-CRNTI and determine that the RA procedure completed successfully.

[0139] In some embodiments, terminal device 110 may receive a PDCCH transmission from a candidate cell addressed to the RNTI of terminal device 110 associated with the candidate cell. In this case, terminal device 110 may determine that an RAR has been received. In some embodiments, if a PDCCH transmission is received, terminal device 110 may determine that the RA procedure has completed successfully.

[0140] The method 500 may implement an RA procedure for a candidate cell of an LTM.

[0141] 6 illustrates another exemplary communication method 600 implemented in a terminal device according to some embodiments of the present disclosure. For example, method 600 may be performed in terminal device 110 as shown in FIG. 1A. For purposes of explanation, method 600 will be described below with reference to FIG. 1A. It should be understood that method 600 may include additional blocks not shown and / or omit some blocks that are shown, and that the scope of the present disclosure is not limited in this respect.

[0142] In block 610, terminal device 110 receives a DCI from a serving cell (e.g., cell 121) that triggers an RA procedure on a candidate cell (e.g., cell 131) from a set of candidate cells that allow LTM. The DCI includes a value of a power ramping counter for the preamble.

[0143] In block 620, terminal device 110 determines a received target power for the preamble based on the value of the power ramping counter.

[0144] In block 630, the terminal device 110 transmits a preamble for the RA procedure to the candidate cell based on the received target power.

[0145] By the method 600, preamble transmission to a candidate cell for LTM can be achieved without RAR.

[0146] 7 illustrates yet another exemplary communication method 700 implemented in a terminal device, according to some embodiments of the present disclosure. For example, method 700 may be performed in terminal device 110 as shown in FIG. 1A. For purposes of explanation, method 700 will be described below with reference to FIG. 1A. It should be understood that method 700 may include additional blocks not shown and / or omit some blocks that are shown, and that the scope of the present disclosure is not limited in this respect.

[0147] In block 710, the terminal device 110 may receive a first DCI from a serving cell (e.g., cell 121) that triggers an RA procedure on a candidate cell (e.g., cell 131) from a set of candidate cells that allow LTM.

[0148] At block 720, terminal device 110 may transmit a preamble for the RA procedure to the candidate cell.

[0149] At block 730, terminal device 110 may receive a second DCI from the serving cell indicating whether the RA procedure completed successfully.

[0150] In some embodiments, when a first DCI is received, terminal device 110 may start a timer and monitor for a second DCI while the timer is running. In some embodiments, when the timer expires, terminal device 110 may determine that the RA procedure has completed successfully. In some embodiments, when the timer expires, terminal device 110 may determine that the RA procedure has not completed successfully.

[0151] In some embodiments, if the RA procedure is not completed successfully, terminal device 110 may perform an RA resource selection procedure in which a power ramping counter for the preamble is increased.

[0152] The process 700 may implement an RA procedure for a candidate cell for LTM.

[0153] It should be noted that the operations of methods 500-700 are similar to those described in connection with FIGS. 2-4 and, therefore, for the sake of brevity, other details will not be repeated here. Device and equipment implementation examples

[0154] 8 is a schematic block diagram of an apparatus 800 suitable for implementing an embodiment of the present disclosure. The apparatus 800 may be regarded as another exemplary implementation of the terminal apparatus 110 or the network apparatus 120 shown in FIG. 1A, or the CU 141, the DU 151, or the DU 152 shown in FIG. 1D. Thus, the apparatus 800 may be implemented in the terminal apparatus 110, the network apparatus 120, the CU 141, or the DU 151 or 152, or as at least a part thereof.

[0155] As shown, the apparatus 800 comprises a processor 810, a memory 820 coupled to the processor 810, a suitable transmitter (TX) and receiver (RX) 840 coupled to the processor 810, and a communication interface coupled to the TX / RX 840. The memory 810 stores at least a portion of a program 830. The TX / RX 840 is used for bidirectional communication. The TX / RX 840 has at least one antenna to facilitate communication, although the access nodes referred to herein may in practice have multiple antennas. The communication interface may represent any interface required for communication with other network elements, such as an X2 / Xn interface for bidirectional communication between eNBs / gNBs, an S1 / NG interface for communication between a Mobility Management Entity (MME) / Access and Mobility Management Function (AMF) / SGW / UPF and an eNB / gNB, an Un interface for communication between an eNB / gNB and a Relay Node (RN), or a Uu interface for communication between an eNB / gNB and a terminal device.

[0156] 1A-7, which, when executed by the associated processor 810, enables the device 800 to operate according to embodiments of the present disclosure. The embodiments herein may be implemented by computer software executable by the processor 810 of the device 800, by hardware, or by a combination of software and hardware. The processor 810 may be configured to implement various embodiments of the present disclosure. Furthermore, the combination of the processor 810 and the memory 820 may form a processing means 850 suitable for implementing various embodiments of the present disclosure.

[0157] Memory 820 may be of any type suitable for a local technology network and may be implemented using any suitable data storage technology, including, by way of non-limiting example, non-transitory computer-readable storage media, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. While only one memory 820 is shown in device 800, there may be several physically distinct memory modules within device 800. Processor 810 may be of any type suitable for a local technology network and may include, by way of non-limiting example, one or more of 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. Device 800 may have multiple processors, for example, application-specific integrated circuit chips time-slaved to a clock that synchronizes the main processor.

[0158] In some embodiments, a terminal device comprises circuitry configured to receive, from a serving cell, downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmit a preamble for the random access procedure to the candidate cell, monitor a physical downlink control channel on at least one of the serving cell or the candidate cell, and receive a random access response from the at least one of the serving cell or the candidate cell.

[0159] In some embodiments, a terminal device comprises circuitry configured to receive, from a serving cell, downlink control information including a value of a power ramping counter for a preamble, the downlink control information triggering a random access procedure on a candidate cell from a set of candidate cells that allow layer 1 or layer 2 triggered mobility; determine a reception target power for the preamble based on the value of the power ramping counter; and transmit the preamble for the random access procedure to the candidate cell based on the reception target power.

[0160] In some embodiments, a terminal device comprises circuitry configured to receive, from a serving cell, first downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmit a preamble for the random access procedure to the candidate cell, and receive, from the serving cell, second downlink control information indicating whether the random access procedure has been completed successfully.

[0161] As used herein, the term "circuitry" may refer to a hardware circuit and / or a combination of a hardware circuit and software. For example, a circuit may be a combination of analog and / or digital hardware circuitry and software / firmware. As yet another example, a circuit may be any portion of a hardware processor with software, including a digital signal processor, software, and one or more memories, that cooperate to cause a device, such as a terminal device or a network device, to perform various functions. In yet another example, a circuit may be a hardware circuit and / or a processor, such as a microprocessor or portion thereof, that requires software / firmware for operation, although software may not be present if not necessary for operation. As used herein, the term "circuitry" also includes an implementation of a hardware circuit or one or more processors only, or a hardware circuit or portion of one or more processors and its / their associated software and / or firmware.

[0162] In summary, the embodiments of the present disclosure can provide the following solutions:

[0163] In one solution, a terminal device comprises a processor, the processor being configured to cause the terminal device to receive, from a serving cell, downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow mobility triggered by Layer 1 or Layer 2, transmit a preamble for the random access procedure to the candidate cell, perform monitoring of a physical downlink control channel on at least one of the serving cell or the candidate cell, and receive a random access response from the at least one of the serving cell or the candidate cell.

[0164] In some embodiments, the random access response includes a timing advance command for the candidate cell.

[0165] In some embodiments, the terminal device performs at least one of receiving the random access response from the serving cell, transmitting the preamble on a random access resource dedicated to the candidate cell, or monitoring the physical downlink control channel based on a search space dedicated to the candidate cell. In some embodiments, the random access response includes information of the candidate cell.

[0166] In some embodiments, the candidate cell belongs to a timing advance group, and the terminal device further performs at least one of applying the timing advance command for the timing advance group, starting or restarting a timer for time alignment associated with the timing advance group, or maintaining the timing advance of the timing advance group according to a determination that the timer has expired.

[0167] In some embodiments, the terminal device further performs the steps of receiving a media access control control element from the serving cell indicating a cell switch to the candidate cell, and setting the timing advance group as the primary timing advance group of the terminal device.

[0168] In some embodiments, the terminal device further performs the following: determining that the random access procedure has been completed successfully in accordance with a determination that the random access response includes a media access control sub-protocol data unit and that the media access control sub-protocol data unit is a media access control sub-header having only a random access preamble identity; determining that the random access procedure has been completed successfully in accordance with a determination that the random access response does not include an uplink grant; or determining that the random access procedure has been completed successfully and ignoring the uplink grant in accordance with a determination that the random access response includes the uplink grant.

[0169] In some embodiments, the terminal device further performs, in accordance with a determination that the random access response has been successfully received, transmitting a message including an identity of the terminal device to the candidate cell using an uplink grant scheduled within the random access response.

[0170] In some embodiments, the identity of the terminal device is a radio network temporary identity of the terminal device associated with the candidate cell.

[0171] In some embodiments, the identity of the terminal device is carried in a first media access control control element.

[0172] In some embodiments, the terminal device further starts a timer for contention resolution and monitors a physical downlink control channel of the candidate cell while the timer is running.

[0173] In some embodiments, the terminal device further performs receiving a physical downlink control channel transmission from the candidate cell addressed to a radio network temporary identity of the terminal device associated with the candidate cell, and determining that contention resolution is successful.

[0174] In some embodiments, the terminal device further performs the following: stopping the timer for conflict resolution; discarding a temporary cell radio network temporary identity of the terminal device; and determining that the random access procedure has completed successfully.

[0175] In some embodiments, the terminal device further performs the following: receiving a physical downlink control channel transmission from the candidate cell addressed to a temporary cell radio network temporary identity of the terminal device; stopping the timer for conflict resolution in accordance with determining that a media access control protocol data unit has been successfully decoded; and determining that conflict resolution has been successful in accordance with determining that the media access control protocol data unit includes a second media access control control element that matches content in the message.

[0176] In some embodiments, the terminal device further performs the steps of: discarding the temporary cell radio network temporary identity of the terminal device; and determining that the random access procedure has completed successfully.

[0177] In some embodiments, the terminal device receives the random access response by receiving a physical downlink control channel transmission from the candidate cell addressed to a radio network temporary identity of the terminal device associated with the candidate cell. In some embodiments, the terminal device further determines that the random access procedure has been successfully completed according to determining that the physical downlink control channel transmission has been received.

[0178] In another solution, a terminal device comprises a processor, and the processor is configured to cause the terminal device to perform the following: receive downlink control information from a serving cell, the downlink control information including a value of a power ramping counter for a preamble, the downlink control information triggering a random access procedure on a candidate cell from a set of candidate cells that allow mobility triggered by layer 1 or layer 2; determine a reception target power for the preamble based on the value of the power ramping counter; and transmit the preamble for the random access procedure to the candidate cell based on the reception target power.

[0179] In another solution, a terminal device comprises a processor, the processor being configured to cause the terminal device to receive, from a serving cell, first downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmit a preamble for the random access procedure to the candidate cell, and receive, from the serving cell, second downlink control information indicating whether the random access procedure has been completed successfully.

[0180] In some embodiments, the terminal device receives the second downlink control information by starting a timer in accordance with determining that the first downlink control information has been received, and monitoring for the second downlink control information while the timer is running.

[0181] In some embodiments, the terminal device further performs the following in accordance with determining that the timer has expired: determining that the random access procedure has been completed successfully; or determining that the random access procedure has not been completed successfully in accordance with determining that the timer has expired.

[0182] In some embodiments, the terminal device further performs a random access resource selection procedure in which a power ramping counter for the preamble is increased in accordance with a determination that the random access procedure was not completed successfully.

[0183] In another solution, a method of communication includes, in a terminal device, receiving from a serving cell downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmitting a preamble for the random access procedure to the candidate cell, performing monitoring of a physical downlink control channel on at least one of the serving cell or the candidate cell, and receiving a random access response from the at least one of the serving cell or the candidate cell.

[0184] In another solution, a communication method includes receiving, in a terminal device, downlink control information from a serving cell, the downlink control information including a value of a power ramping counter for a preamble, the downlink control information triggering a random access procedure on a candidate cell of a set of candidate cells that allow layer 1 or layer 2 triggered mobility; determining a reception target power for the preamble based on the value of the power ramping counter; and transmitting the preamble for the random access procedure to the candidate cell based on the reception target power.

[0185] In another solution, a method of communication includes, in a terminal device, receiving from a serving cell first downlink control information triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility, transmitting a preamble for the random access procedure to the candidate cell, and receiving from the serving cell second downlink control information indicating whether the random access procedure has been completed successfully.

[0186] Overall, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software executable by a controller, microprocessor, or other computing device. While various aspects of embodiments of the present disclosure have been illustrated and described using block diagrams, flowcharts, or other pictorial representations, it should be understood that the blocks, devices, systems, techniques, or methods described herein may be implemented, by way of non-limiting example, in hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing device, or any combination thereof.

[0187] 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, that execute within a device on a target real or virtual processor to perform the processes or methods described above with reference to FIGS. 1A-7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various embodiments, the functionality of the program modules may be combined or split between program modules as desired. The machine-executable instructions of the program modules may be executed within local or distributed devices. In a distributed device, program modules may be located in both local and remote storage media.

[0188] Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, and when executed by the processor or controller, cause the program code to implement the functions / acts specified in the flowcharts and / or block diagrams. The program code may run entirely on the machine, partially on the machine, as a separate software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0189] The above-described program code may be embodied on a machine-readable medium, which may be any tangible medium that can contain or store a program used by or associated with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the aforementioned media. More specific examples of a machine-readable storage medium may 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 above.

[0190] It should be noted that, although operations have been described in a particular order, it should not be understood that performing such operations in the particular order shown, or in any sequential order, or performing all of the operations described, is required to achieve desirable results. In some cases, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the above discussion, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Some features that are described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0191] 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, as defined in the appended claims, is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A terminal device including a processor, The processor causes the terminal device to receiving, from a serving cell, downlink control information for triggering a random access procedure on a candidate cell of a set of candidate cells that allow layer 1 or layer 2 triggered mobility; transmitting a preamble for the random access procedure to the candidate cell; performing monitoring of a physical downlink control channel on at least one of the serving cell or the candidate cell; receiving a random access response from the at least one of the serving cell or the candidate cell. Terminal device.

2. The random access response includes a timing advance command for the candidate cell. The terminal device according to claim 1 .

3. receiving the random access response from the serving cell; transmitting the preamble on a random access resource dedicated to the candidate cell; or performing monitoring of the physical downlink control channel based on a search space dedicated to the candidate cell. The terminal device according to claim 1 .

4. The random access response includes information of the candidate cell. The terminal device according to claim 3 .

5. the candidate cell belongs to a timing advance group; applying the timing advance command for the timing advance group; starting or restarting a timer for time alignment associated with said timing advance group; or maintaining the timing advance of the timing advance group in accordance with determining that the timer has expired. The terminal device according to claim 1 .

6. receiving a media access control control element from the serving cell indicating a cell switch to the candidate cell; setting the timing advance group as a primary timing advance group for the terminal device. The terminal device according to claim 5.

7. determining that the random access procedure has been successfully completed in accordance with a determination that the random access response includes a media access control sub-protocol data unit, and that the media access control sub-protocol data unit is a media access control sub-header having only a random access preamble identity; or determining that the random access procedure has been successfully completed according to a determination that the random access response does not include an uplink grant; or and determining that the random access procedure has been successfully completed and ignoring the uplink grant according to determining that the random access response includes the uplink grant. The terminal device according to claim 1 .

8. and, in accordance with determining that the random access response has been successfully received, transmitting a message to the candidate cell using an uplink grant scheduled in the random access response, the message including an identity of the terminal device. The terminal device according to claim 1 .

9. The identity of the terminal device is a radio network temporary identity of the terminal device associated with the candidate cell. The terminal device according to claim 8.

10. The identity of the terminal device is carried in a first media access control control element. The terminal device according to claim 8.

11. starting a timer for conflict resolution; monitoring a physical downlink control channel of the candidate cell while the timer is running; and The terminal device according to claim 8.

12. receiving a physical downlink control channel transmission from the candidate cell addressed to a radio network temporary identity of the terminal device associated with the candidate cell; Determining that conflict resolution was successful and performing further The terminal device according to claim 11.

13. stopping the timer for conflict resolution; Revoke a temporary cell radio network identity of the terminal device; determining that the random access procedure has been successfully completed; and The terminal device according to claim 12.

14. receiving a physical downlink control channel transmission from the candidate cell addressed to a temporary cell radio network temporary identity of the terminal device; stopping the timer for contention resolution in response to determining that the media access control protocol data unit has been successfully decoded; determining that the contention resolution is successful in accordance with determining that the media access control protocol data unit includes a second media access control control element that matches content in the message. The terminal device according to claim 11.

15. Revoke the temporary cell radio network temporary identity of the terminal device; determining that the random access procedure has been successfully completed; and The terminal device according to claim 14.

16. receiving the random access response by receiving a physical downlink control channel transmission from the candidate cell addressed to a radio network temporary identity of the terminal device associated with the candidate cell. The terminal device according to claim 1 .

17. and determining that the random access procedure has been successfully completed in accordance with determining that the physical downlink control channel transmission has been received. The terminal device according to claim 16.

18. A terminal device including a processor, The processor causes the terminal device to receiving, from a serving cell, downlink control information including a value of a power ramping counter for a preamble, the downlink control information triggering a random access procedure on a candidate cell of a set of candidate cells that allow Layer 1 or Layer 2 triggered mobility; determining a receive target power for the preamble based on a value of the power ramping counter; transmitting the preamble for the random access procedure to the candidate cell based on the reception target power. Terminal device.

19. A terminal device including a processor, The processor causes the terminal device to receiving, from a serving cell, first downlink control information that triggers a random access procedure on a candidate cell of a set of candidate cells that allow layer 1 or layer 2 triggered mobility; transmitting a preamble for the random access procedure to the candidate cell; receiving, from the serving cell, second downlink control information indicating whether the random access procedure has been successfully completed. Terminal device.

20. receiving the second downlink control information by starting a timer in response to determining that the first downlink control information has been received and monitoring for the second downlink control information while the timer is running.

20. The terminal device according to claim 19.

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