Wireless communication method and user equipment

Abstract

The present application provides a wireless communication method and a user equipment, which can reduce the delay and interruption of inter-cell mobility. In one embodiment, the wireless communication method provided by the present application can include: a user equipment in a serving cell of a mobile communication network receiving a configuration, the configuration including an active set of cells; the user equipment performing pre-synchronization and measurement with each active cell in the active set of cells based on the configuration, wherein the user equipment maintains downlink (DL) synchronization with each active cell; the user equipment receiving a cell handover command from the mobile communication network to hand over from the serving cell to a target cell belonging to the active set of cells; and after receiving the handover command, the user equipment applying RRC configuration of the target cell.

Description

Technical Field

[0001] This invention generally relates to wireless communication, and more specifically to methods for enhancing mobility in 5G New Radio (NR) cellular communication networks. Background Technology

[0002] Wireless communication networks have grown exponentially over the years. Long-Term Evolution (LTE) systems offer high peak data rates, low latency, improved system capacity, and low operating costs due to a simplified network architecture. LTE systems, also known as 4G systems, also provide seamless integration with older wireless networks such as GSM, CDMA, and the Universal Mobile Telecommunication System (UMTS). In LTE systems, the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) comprises multiple evolved Node-Bs (eNodeBs or eNBs) that communicate with multiple mobile stations known as User Equipment (UEs). 3GPP networks typically include a hybrid of 2G / 3G / 4G systems. The Next Generation Mobile Network (NGMN) committee has decided to focus future NGMN activities on defining end-to-end requirements for 5G New Radio (NR) systems. In 5G NR, base stations are also referred to as gNodeBs or gNBs.

[0003] 5G NR frequency bands are divided into two distinct frequency ranges. Frequency range 1 (FR1) includes sub-6GHz bands, some of which were used in previous standards but have been expanded to cover potentially new spectrum from 410MHz to 7125MHz. Frequency range 2 (FR2) includes bands from 24.25GHz to 52.6GHz. Compared to the bands in FR1, the band range in FR2 within the millimeter wave range is shorter but offers greater available bandwidth. For UEs in Radio Resource Control (RRC) connected mode mobility, cell selection is the process by which the UE selects a specific cell for initial registration after power-on, while cell reselection is the mechanism by which the UE changes cells after camping on a cell and entering connected mode. For UEs in RRC connected mode mobility, handover is the process by which the UE switches an ongoing session from a source gNB to a neighboring target gNB.

[0004] With the narrower, more numerous, and denser deployments of 5G NR, no always-on cell reference signal is available, posing new challenges to High Data Rate Low Latency (HDRLL) applications. UEs may encounter issues such as channel fluctuations, coverage blind spots, shorter beam / cell dwell times, and longer measurement periods. More frequent cell handovers result in longer overall interruption times due to handover (e.g., approximately 75 milliseconds per cell change), and poor robustness with higher mobility failure rates (e.g., FRI < 1% and FR2 > 10%) leads to even longer interruptions. A solution is needed to mitigate these adverse mobility performance impacts. Summary of the Invention

[0005] This invention provides a wireless communication method and user equipment that can reduce delays and interruptions in inter-cell mobility.

[0006] In one embodiment, the wireless communication method provided by the present invention may include: a user equipment in a serving cell of a mobile communication network receiving a configuration including an active set of cells; the user equipment performing pre-synchronization and measurement with each active cell in the active set of cells based on the configuration, wherein the user equipment maintains downlink (DL) synchronization with each active cell; the user equipment receiving from the mobile communication network a cell handover command for handover from the serving cell to a target cell belonging to the active set of cells; and after receiving the handover command, the user equipment applying the RRC configuration of the target cell.

[0007] In another embodiment, the user equipment provided by the present invention may include: a transceiver that receives a configuration in a serving cell of a mobile communication network, the configuration including an active set of cells; a synchronization circuit that performs pre-synchronization and measurement with each active cell in the active set of cells based on the configuration, wherein the user equipment maintains downlink (DL) synchronization with each active cell; and a handover circuit that receives from the mobile communication network a cell handover command for handover from the serving cell to a target cell belonging to the active set of cells, and applies the RRC configuration of the target cell after receiving the handover command. Attached Figure Description

[0008] Figure 1 An exemplary 5G New Radio (NR) network 100 is shown in accordance with some aspects of the present invention.

[0009] Figure 2 A simplified block diagram of a wireless device (e.g., UE 201 and gNB 211) in a 5G NR network 200 is shown according to some embodiments of the present invention.

[0010] Figure 3 The diagram illustrates multiple base stations with a configured set 310 and an active set 320 for cells to reduce delays and interruptions in UE mobility between cells.

[0011] Figure 4 The following time-domain diagrams illustrate some different embodiments of the measurement and handover process with an active cell set configuration, according to some embodiments of the present invention.

[0012] Figure 5 A message sequence diagram between the UE, source cell, and target cell to support UE mobility with reduced latency and interruptions.

[0013] Figure 6 A novel example of performing pre-RACH for an active cell using an additional MAC / PHY is shown.

[0014] Figure 7 The diagram illustrates the UE behavior for different UE mobility levels after receiving a cell handover command.

[0015] Figure 8 According to a novel aspect of the present invention, a flowchart of a method for performing inter-cell mobility is shown from the perspective of a UE. Detailed Implementation

[0016] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." "Substantially" or "approximately" means that, within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect. Furthermore, the terms "coupled" or "coupled" herein include any direct and indirect electrical connection means. Therefore, if a first device is described as coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means.

[0017] The following description is for illustrative purposes only and should not be construed as limiting. The scope of the invention is best determined by referring to the appended claims.

[0018] Figure 1According to some aspects of the present invention, an exemplary 5G New Radio (NR) network 100 is illustrated. The 5G NR network 100 supports an active cell set configuration to reduce latency and interruptions in inter-cell mobility. The 5G NR network 100 includes a User Equipment (UE) 101 and multiple base stations (including gNB 102 and gNB 103). The UE 101 is communicatively connected to the serving gNB 102, which provides radio access using Radio Access Technology (RAT) technology (e.g., 5G NR technology). The UE 101 may be a smartphone, wearable device, Internet of Things (IoT) device, tablet computer, etc. Alternatively, the UE 101 may be a notebook computer (NB) or personal calculator (PC) with a data card containing a modem and radio frequency transceiver to provide wireless communication capabilities inserted or installed.

[0019] The core 5G function receives all connection and session-related information and is responsible for connection and mobility management tasks. For UEs in Radio Resource Control (RRC) connected mode mobility, cell selection is the process by which the UE selects a specific cell for initial registration after power-on, while cell reselection is the mechanism by which the UE changes cells after camping on a cell and entering connected mode. For UEs in RRC connected mode mobility, handover is the process by which the UE switches an ongoing session from the source gNB to an adjacent target gNB. With the narrower beamwidth, more beamwidth, and denser deployment of 5G NR, there are no always-on cell reference signals available, posing new challenges to High Data Rate Low Latency (HDRLL) applications. UEs may encounter issues such as channel fluctuations, coverage blind spots, shorter beamwidth / cell dwell times, and longer measurement periods. More frequent cell handovers result in longer overall interruption times due to handover (e.g., approximately 75 milliseconds per cell change), and poorer robustness with higher mobility failure rates (e.g., FRI < 1% and FR2 > 10%) leads to longer interruptions.

[0020] exist Figure 1In the example, at an early point in time, gNB 102 may be considered the best cell, providing communication coverage for the geographic coverage area that supports communication with UE 101 via communication link / beam 110. Later, gNB 103 may become the best cell, providing communication coverage for the geographic coverage area that supports communication with UE 101 via communication link / beam 120. Note that UE 101 is not always served by the best cell / beam due to mobility latency (due to time spent on measurement reporting, handover commands, and handover execution). Data may be interrupted during handover for UE reconfiguration and synchronization. In cases of short cell / beam dwell times (e.g., in FR2), the percentage of time the UE is served by a poor cell / beam or experiences service interruptions may be significant. Ideally, the mobility delays for beam switching within a Transmission and Reception Point (TRP), between intra-cell inter-TRPs, and between inter-cells should be similar.

[0021] According to a novel aspect of the invention, a method is provided for configuring an active set of cells across multiple neighboring cells to reduce inter-cell mobility latency and interruptions. The active set of cells is an active set of cells in which a UE can perform fast cell handover. Each cell in the active set is a candidate target cell for handover. The active set of cells (i.e., the active cell set) is configured by the network based on the UE's measurement reports or network deployment information (this configuration includes the RRC configuration forming the active set of cells). The UE maintains the configuration result and can perform pre-synchronization of the configured multiple active cells only in the downlink (DL) or in both the downlink and uplink (UL). The UE maintains DL / UL synchronization with the multiple active cells, and once the UE is instructed to handover to an active cell as a target cell, the UE applies the configuration (for that target cell, the UE applies the RRC configuration of that target cell). Because the UE maintains the target cell configuration and the target cell's DL / UL timing (maintaining the target cell's DL / UL timing means maintaining DL / UL synchronization with the target cell) before receiving the cell handover command (as shown in box 130), the mobility delay and interruption time of inter-cell mobility are reduced.

[0022] Figure 2Simplified block diagrams of wireless devices (e.g., UE 201 and gNB 211) in a 5G NR network 200 are shown according to some embodiments of the present invention. gNB 211 includes an antenna 215 for transmitting and receiving radio signals. A radio frequency (RF) transceiver 214, coupled to the antenna 215, is used to receive RF signals from the antenna 215 and convert the received signals into baseband signals for transmission to a processor 213. The RF transceiver 214 is also used to convert baseband signals received from the processor 213 into RF signals and transmit the converted RF signals back to the antenna 215. The processor 213 processes the received baseband signals and invokes different functional modules to perform functions in gNB 211. A memory 212 stores program instructions and data 220 to control the operation of gNB 211. Figure 2 In the example, gNB 211 also includes a protocol stack 280 and a set of control function modules and circuits 290. Protocol stack 280 may include a Non-Access-Stratum (NAS) layer for communicating with AMF / SMF / MME entities connected to the core network, a Radio Resource Control (RRC) layer for higher-layer configuration and control, a Packet Data Convergence Protocol / Radio Link Control (PDCP / RLC) layer, a Media Access Control (MAC) layer, and a Physical (PHY) layer. In one example, control function modules and circuits 290 include configuration circuitry 291 for configuring measurement reports and activation sets for the UE, and handover processing circuitry 292 for sending cell handover decisions to the UE.

[0023] Similarly, UE 201 includes memory 202, processor 203, and RF transceiver 204. RF transceiver 204 is coupled to antenna 205, receives RF signals from antenna 205, converts them into baseband signals, and sends them to processor 203. RF transceiver 204 also converts received baseband signals from processor 203 into RF signals and sends them to antenna 205. Processor 203 processes the received baseband signals (e.g., including SCell / PSCell add / activate commands) and invokes different functional modules and circuits to execute features in UE 201. Memory 202 stores data and program instructions 210 to be executed by processor 203 to control the operation of UE 201. As examples, suitable processors include special-purpose processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, application-specific integrated circuits (ASICs), file-programmable gate arrays (FPGAs), and other types of integrated circuits (ICs) and / or state machines. Software-associated processors can be used to implement and configure the features of UE 201.

[0024] UE 201 also includes a protocol stack 260 and a set of control function modules and circuits 270. Protocol stack 260 may include a NAS layer for communicating with AMF / SMF / MME entities connected to the core network, an RRC layer for higher-level configuration and control, a PDCP / RLC layer, a MAC layer, and a PHY layer. Control function modules and circuits 270 may be implemented and configured through software, firmware, hardware, and / or combinations thereof. When executed by processor 203 via program instructions contained in memory 202, control function modules and circuits 270 cooperate to allow UE 201 to perform embodiments, functional tasks, and features within the network. In one embodiment, control function modules and circuits 270 include configuration circuitry 271 for acquiring measurement and configuration information for the active set, measurement circuitry 272 for performing and reporting measurements, and synchronization / handover processing circuitry 273 for performing pre-synchronization and handover procedures based on configuration and cell handover commands received from the network.

[0025] Figure 3 The diagram illustrates multiple base stations with a configured set 310 and an active set 320 for each cell, designed to reduce latency and interruptions in UE mobility between cells. UE mobility can be based on L1, L2, or L3. Figure 3 In the example shown, active set 320 includes multiple cells served by base stations gNB301, gNB302, and gNB303. The remaining base stations belong to configuration set 310. UE 304 is initially served by cell #1 and receives the RRC configuration of the active cell set. This active cell set is a group of cells for which the UE can perform fast cell handover. The active cell set of UE 304 is configured by the network based on UE measurement reports or network deployment information (this configuration includes the RRC configuration that forms the active cell set). Cells in the active set retain the UE's context information. UE 304 maintains the configuration result of this configuration and can perform pre-synchronization of the configured multiple active cells only in the downlink (DL) or in both the downlink and uplink (UL). UE 304 maintains DL / UL synchronization with the multiple active cells, and once the UE is instructed to handover to a target cell (e.g., cell #2), the UE applies the RRC configuration of that target cell (from the multiple active cells).

[0026] The active cell set is a list of highly probable candidate target cells. The active set can change rapidly when the UE moves, thus requiring a suitable active set management scheme. In a preferred embodiment, a two-step active set configuration scheme is provided. In step 1, the network provides configurations for multiple cells in a configuration set (e.g., denoted as configuration set 310). In step 2, a subset of cells in the configuration set is considered the active set (e.g., active set 320). Multiple cells can be activated / deactivated based on measurement / beam reports via MAC CE (Medium Access Control Control Element). For the configuration set, multiple cells are prepared (i.e., UE context information is processed), and the UE processes and maintains the RRC configurations for these multiple cells. For the active set, the UE can quickly handover between multiple active cells. The UE maintains DL / UL synchronization with multiple active cells, and once the UE is instructed to handover to an active cell, the UE applies the configuration (for that active cell, the UE applies the RRC configuration of that active cell). In one embodiment, the active set may be combined with a list of active Transmission Configuration Indicator (TCI) states. A cell having at least one relevant TCI state in the state list is an active cell. An active TCI state may refer to a TCI state activated by MACCE for control in DL and / or UL and / or a TCI state under the Quasi Co-Location (QCL) assumption for the data channel. The UE performs fine time-frequency tracking on the inter-cell reference signal associated with an active TCI state.

[0027] Figure 4 The following time-domain diagrams illustrate some different embodiments of the measurement and handover process with an active cell set configuration, according to some embodiments of the present invention. Figure 4 (A) shows a time-domain diagram of the measurement and handover process at the baseline. In step (1), the UE sends a measurement report to the network. In step (2), a handover decision and preparation are made due to the UE's movement. In step (3), the UE receives a handover command from the network. Steps (4)-(7) are the time periods for performing RRC processing, UE processing, obtaining the first Synchronization Signal Block (SSB), and SSB processing. In step (8), the UE waits for a random access opportunity. In step (9), the UE performs random access by sending a Random-Access Channel (RACH) preamble to the network. In steps (10) and (11), the UE waits for and receives a Random Access Response (RAR) from the network. In step (12), the UE waits for an uplink grant (UL Grant) for the handover completion message. In step (13), the UE sends a handover completion message, thereby completing the handover. As shown in 410, the entire data interruption time lasts from step (4) to step (13) (including steps (4)-(13)).

[0028] Figure 4(B) shows a time-domain diagram of the measurement and handover process when an active cell set is configured to the UE. The UE first receives the RRC configuration of the active cell list (i.e., the active cell set / active set of cells). The UE then maintains the RRC configuration and DL timing of the active cell list. Finally, the UE can run time tracking ahead of time (e.g., steps (4)-(7)) to reduce the corresponding downtime. After time tracking, in step (1), the UE sends a measurement report to the network. In step (2), a handover decision and preparation are made due to the UE's movement. In step (3), the UE receives a handover command from the network. In step (8), the UE waits for a random access opportunity. In step (9), the UE performs random access by sending a RACH preamble to the network. In steps (10) and (11), the UE waits for and receives a Random Access Response (RAR) from the network. In step (12), the UE waits for an uplink grant (UL Grant) for the handover completion message. In step (13), the UE sends a handover completion message, thereby completing the handover. As shown in 420, the entire data interruption time lasts from step (4) to step (13) (including steps (4), (8)-(13)). It can be seen that the data interruption time is reduced due to the configuration of the active cell list (which allows the UE to perform time tracking of candidate target cells before receiving the handover command). Since multiple active cells have already processed the UE context based on the handover trigger, the time for step (2) is also shortened. Furthermore, the source data may still continue until some point before RACH.

[0029] Figure 4(C) shows a time-domain diagram of the measurement and handover process when an active cell set is configured for a UE supporting pre-RACH. The UE first receives the RRC configuration of the active cell list. The UE then maintains the RRC configuration and DL timing of the active cell list. Finally, the UE can run time tracking ahead of time (e.g., steps (4)-(7)) to reduce the corresponding downtime. In step (8), the UE waits for the random access opportunity. In step (9), the UE performs random access by sending a RACH preamble to the network. In steps (10) and (11), the UE waits for and receives a random access response (RAR) from the network. After the time tracking and RACH process, the UE obtains downlink and uplink synchronization for candidate cells. Then, in step (1), the UE sends a measurement report to the network. In step (2), a handover decision and preparation are made due to the UE's movement. In step (3), the UE receives a handover command from the network. In step (12), the UE waits for an uplink grant (UL Grant) for the handover completion message. In step (13), the UE sends a handover completion message, thereby completing the handover. As shown in 430, the entire data interruption time lasts from step (3) to step (13) (including steps (3), (12)-(13)) (in other optional embodiments, Figure 4 The interruption time in (C) can also include only steps (4), (12)-(13)). It can be seen that the data interruption time is reduced due to the configuration of the active cell list (allowing the UE to perform time tracking of candidate target cells before receiving the handover command). Since multiple active cells have already processed the UE context based on the handover trigger, the time for step (2) is also shortened. Furthermore, the source data may still continue until a point in time before RACH. Figure 4 In (C), for UEs with the corresponding capabilities, the RACH process can be performed in advance for the list of active cells, thereby further reducing the data interruption time between cell handovers.

[0030] Figure 5A message sequence diagram is provided to support UE mobility with reduced latency and interruptions between the UE, source cell, and target cell. In step 511, UE 501 sends and receives data with the source base station (i.e., the source gNB) in the source cell. In step 512, UE 501 sends measurement reports from multiple neighboring cells to the source gNB. In step 513, the source gNB makes a handover decision and sends a preparation request to a target base station (i.e., the target gNB). In step 514, the target gNB sends a preparation acknowledgment back to the source gNB. The source gNB can then provide UE 501 with the RRC configuration of the active cell set. The RRC configuration includes information on synchronization and measurement performed by the UE on the active cell, as well as public and private configurations including those for when the active cell becomes the UE's serving cell.

[0031] There are two activation set configuration schemes. In the first alternative one-step configuration scheme, the source gNB directly provides the activation set via RRC signaling messages (step 521). RRC messages can add cells to the activation set, change cells in the activation set, or remove cells from the activation set. RRC messages can also inform the UE whether to retain the activation set after handover. In the second alternative two-step configuration scheme, the source gNB first provides the configuration set via RRC signaling messages (step 531), receives measurement or beam reports from UE 501 (step 532, optional), and then provides UE 501 with activation signaling for the activation set (via MAC CE command) (step 533). That is, RRC can configure a "configuration set," and then MAC CE can be used to activate or deactivate multiple cells (adding or removing cells from the activation set). In one example, if the number of cells in the configuration set is less than a threshold (e.g., 1 or 2), all cells in the configuration set are active. In another example, certain cells in the configuration set (e.g., the first cell) are considered active cells before activation signaling is received.

[0032] After the active set is configured and activated, in step 541, UE 501 performs synchronization on the cells in the active set. In the downlink, UE 501 performs fine time-frequency tracking on at least some beams of multiple active cells. In the uplink, UE 501 performs pre-RACH for timing advance (this step is optional). In step 542, UE 501 sends a measurement or beam report to the source gNB. In step 551, the source gNB makes a cell handover decision. In step 552, the source gNB sends a cell handover command to UE 501. Based on the received cell handover command, in step 553, UE 501 applies the configuration of the target cell. The cell handover command can be L1 / L2 / L3 signaling. In step 561, UE 501 detaches from the source cell, but UE 501 may retain the configuration of the source cell. In step 562, the handover process is complete. In step 571, UE 501 begins data transmission and reception in the target cell. In an optional implementation, when the UE capability allows, the UE may selectively perform RACH (e.g., pre-RACH) to the target cell. RACH may be performed in step 554 or step 541 to maintain UL synchronization between the UE and the target cell.

[0033] Figure 6 This illustrates a novel example of performing pre-RACH for an active cell using additional MAC / PHY. The UE can selectively perform pre-RACH for cells with active centralized configuration. In one example, the UE may run Time-division multiplexing (TDM) (i.e., temporarily detaching from the source cell to send a preamble to another cell and receive a RAR from that other cell), but RAR monitoring implies an interruption. In another example, the RAR may be sent from the source gNB601, meaning the UE does not need to wait for an uncertain RAR from the target cell. In yet another example, the UE may use additional MAC / PHY for RACH of other cells (e.g., neighboring cell gNB602). Whether the UE should perform pre-RACH for an active cell can be determined based on the UE's capabilities. The network may indicate scheduling gaps for pre-RACH. When the source TA can be reused, or when the target TA = 0, the network may indicate "RACH-less".

[0034] Figure 7This diagram illustrates UE behavior at different mobility levels after receiving a cell handover command. The network architecture contains different types of base stations and network elements, including: Radio Units (RUs) with a PHY layer, Distributed Units (DUs) with PHY, MAC, and RLC layers, Centralized Units (CUs) with RRC and PDCP layers, and the 5G Core (5GC) network. Upon receiving the configuration of an active cell, the UE first processes the MAC / PHY configuration and then maintains it. Once a target cell is selected from the list of active cells by receiving a cell handover command, the MAC / PHY configuration can be quickly applied. As explicitly indicated by the network, L2 / L3 reconfiguration, re-establishment, and key change are not required for intra-DU scenarios, but are required for inter-DU scenarios. Interruptions can be eliminated through an additional protocol stack. The UE is unaware of CU-DU splits; L2 / L3 reconfiguration, re-establishment, and key change are explicitly instructed by the network. If the UE is pre-synchronized with the target cell, it will not repeat the RACH after receiving the handover command. The UE can send a Handover (HO) completion (RRC) message in pre-configured resources. Alternatively, if the cell handover command indicates the target cell TCI state, the UE can receive the PDCCH using the target TCI state after a given interval (i.e., similar to inter-cell beam handover). During this interval, the UE can maintain communication with the source cell, or the UE can be interrupted.

[0035] like Figure 7As shown, based on CU-DU-RU split, mobility can occur at different levels. Example (1) shows intra-DU (intra-cell) mobility, which can be intra-RU or inter-RU. In Example (1), the UE performs traditional L1 / L2 mobility (beam management). Example (2) shows intra-DU (inter-cell) mobility, which can be inter-RU. In Example (2), the UE can perform L1 / L2-centric inter-cell mobility and MAC reset. Example (3) shows intra-CU (intra-CU) mobility, which can be inter-DU. In Example (3), the UE performs RLC re-establishment and MAC reset. Example (4) illustrates inter-CU mobility, in which the UE performs PDCP re-establishment, security key change, RLC re-establishment and MAC reset.

[0036] Figure 8 According to a novel aspect of the invention, a flowchart of a method for performing inter-cell mobility is shown from the perspective of a UE. In step 801, the UE in the serving cell of the mobile communication network receives a configuration, wherein the configuration includes active set information for the cell. In step 802, the UE performs pre-synchronization and measurement with each active cell in the active set based on the configuration, wherein the UE maintains downlink (DL) synchronization with each active cell. In step 803, the UE receives a cell handover command from the mobile communication network for handover from the serving cell to a target cell belonging to the active set. In step 804, after receiving the handover command, the UE applies the RRC configuration of the target cell.

[0037] While the invention has been described by way of example and according to preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments. Rather, it is intended to cover various modifications and similar arrangements (which will be apparent to those skilled in the art). Therefore, the scope of the appended claims should be given the broadest interpretation to cover all such modifications and similar arrangements.

Claims

1. A method of wireless communication, the method comprising: including: a user equipment in a serving cell of a mobile communication network receives a configuration comprising activation set information of cells, wherein a cell is considered to belong to the activation set of the cell when at least one transmission configuration indication state associated with the cell is in a list of activated transmission configuration indication states; the user equipment performs pre-synchronization and measurements based on the configuration with each activated cell in the activation set of the cells, wherein the user equipment maintains downlink synchronization with each activated cell, and the user equipment performs fine time-frequency tracking on inter-cell reference signals associated with the activated transmission configuration indication states; the user equipment receives from the mobile communication network a cell handover command to handover from the serving cell to a target cell belonging to the activation set of the cells; and after receiving the handover command, the user equipment applies radio resource control configuration of the target cell. the activation set of the cells is configured by radio resource control signaling, and the received configuration comprises common and dedicated configuration of the activation set of the cells.

2. The wireless communication method of claim 1, wherein, the user equipment is configured by radio resource control signaling with a configuration set of cells, wherein a subset of the configuration set of the cells is activated by a medium access control control element to become the activation set of the cells.

3. The wireless communication method of claim 1, wherein, the user equipment maintains uplink synchronization with multiple cells in the activation set of the cells by performing a pre-random access channel procedure before receiving the cell handover command.

4. The wireless communication method of claim 1, wherein, the user equipment is equipped with additional physical layer and medium control access layer for performing a pre-random access channel procedure to the target cell.

5. The wireless communication method of claim 4, wherein, the user equipment obtains uplink synchronization with the target cell by performing a pre-random access channel procedure for the target cell after receiving the handover command.

6. The wireless communication method of claim 1, wherein, the user equipment performs radio link control re-establishment and medium access control reset for distributed inter-distributed unit mobility.

7. The wireless communication method of claim 1, wherein, the user equipment performs packet data convergence protocol re-establishment and security key change for centralized inter-central unit mobility.

8. The wireless communication method of claim 1, wherein, including:

9. A user equipment, comprising: a transceiver receives in a serving cell of a mobile communication network a configuration comprising activation set information of cells, wherein a cell is considered to belong to the activation set of the cell when at least one transmission configuration indication state associated with the cell is in a list of activated transmission configuration indication states; a synchronization circuit performs pre-synchronization and measurements based on the configuration with each activated cell in the activation set of the cells, wherein the user equipment maintains downlink synchronization with each activated cell, and the user equipment performs fine time-frequency tracking on inter-cell reference signals associated with the activated transmission configuration indication states; a handover circuit receives from the mobile communication network a cell handover command to handover from the serving cell to a target cell belonging to the activation set of the cells, and after receiving the handover command, applies radio resource control configuration of the target cell. the activation set of the cells is configured by radio resource control signaling, and the received configuration comprises common and dedicated configuration of the activation set of the cells.

10. The user equipment of claim 9, wherein, ​ 11. The user equipment of claim 9, wherein, The user equipment is configured with a set of configurations of cells by radio resource control signaling, wherein a subset of the set of configurations of cells is activated by a medium access control control element to become an active set of cells.

12. The user equipment of claim 9, wherein, The user equipment maintains uplink synchronization with a plurality of cells in the active set of cells by performing a pre-random access channel procedure prior to receiving the cell handover command.

13. The user equipment of claim 12, wherein, The user equipment is equipped with additional physical layer and medium control access layer for performing a pre-random access channel procedure to the target cell.

14. The user equipment of claim 9, wherein, The user equipment obtains uplink synchronization with the target cell by performing a pre-random access channel procedure for the target cell after receiving the handover command.

15. The user equipment of claim 9, wherein, The user equipment performs a radio link control re-establishment and a medium access control reset for distributed inter-distributed unit mobility.

16. The user equipment of claim 9, wherein, The user equipment performs a packet data convergence protocol re-establishment and a security key change for centralized inter-central unit mobility.

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