Method and system for performing fast mobility based on low layer signaling

Abstract

The present disclosure relates to UE measurements and measurement reporting of serving cells, and configurations for cell measurements and reporting to enable fast serving cell changes within a lower network layer, such as Layer 1 or Layer 2 of a wireless communication protocol stack, during UE mobility. The disclosure also relates to signaling procedures associated with UE fast serving cell changes as triggered by a network based on cell measurements and reporting, as well as various lower layer configurations and operations for enabling actual fast serving cell changes at and for the UE.

Description

[0001] This application is a divisional application of the invention patent application with international application number PCT / CN2022 / 088618, international application date April 22, 2022, entering the Chinese national stage on October 21, 2024, Chinese national application number 202280095181.3, and invention name “Method and system for performing fast mobility based on low-layer signaling”. Technical Field

[0002] The present disclosure relates generally to mobility of wireless terminal devices, and in particular to a fast serving cell change procedure triggered by layer 1 or layer 2 signaling. Background Art

[0003] In a cellular wireless access network, each cell may be associated with a coverage area. The coverage areas of multiple cells together provide wireless services to a user equipment (UE). As the UE moves, the cells to which it can connect may change, so the active wireless data connection for the UE may change or switch from one cell to another. Such a cell change or switch may involve complex signaling and operations of various layers of the wireless communication network protocol stack of the UE and the network. Generally, it is preferred to minimize communication overhead and maximize communication efficiency and speed in terms of signaling and operations of cell changes. Summary of the invention

[0004] The present disclosure relates generally to UE mobility in a wireless access network, and in particular to UE measurements and measurement reporting of serving cells, and configurations of cell measurements and reporting for implementing fast serving cell changes during UE mobility within lower network layers (such as layer 1 or layer 2 of a wireless communication protocol stack). The present disclosure also relates to signaling procedures associated with fast serving cell changes of UEs as triggered by the network based on cell measurements and reporting, and various lower layer configurations and operations for implementing the actual fast serving cell changes at and for the UE.

[0005] In some implementations, a method for a serving cell change procedure performed by a wireless device is disclosed. The method may include: receiving a cell measurement and measurement reporting configuration from a wireless communication node; performing cell measurement based on the cell measurement and measurement reporting configuration to generate a cell measurement report associated with the cell measurement; sending the cell measurement report in a cell measurement reporting message according to the cell measurement and measurement reporting configuration, the cell measurement reporting message including a layer 1 or layer 2 control message; and receiving fast serving cell change signaling sent by the wireless communication node in response to the cell measurement report to trigger a serving cell change procedure from a source serving cell of the wireless device to a target serving cell in the wireless device, the serving cell change procedure including a set of serving cell change operations of layers 1 and 2 that are limited to a wireless communication protocol stack of the wireless device.

[0006] In the above implementation, the fast service cell change signaling includes at least one of a layer 1 downlink control indication (DCI) message or a layer 2 MAC CE, and the layer 1 DCI message or the layer 2 MAC CE includes at least one of the following: identification information of the target service cell; beam information indicating which transmission configuration indicator (TCI) state can be activated for uplink and / or downlink communication after the service cell change process; timing advance (TA) information associated with time alignment between the wireless device and the target service cell; a preamble index of a RACH preamble for the wireless device to perform random access to the target service cell; a RACH timing (RO) index for the wireless device to perform random access to the target service cell; a cell radio network temporary identifier (C-RNTI) of the target service cell; or a key code for the wireless device to verify the fast service cell change signaling in layer 1 or layer 2.

[0007] In any of the above implementations, the fast serving cell change signaling may include only a layer 1 DCI message or only a layer 2 MAC CE.

[0008] In any of the above implementations, the fast serving cell change signaling may include both a layer 1 DCI message and a layer 2 MAC CE. The layer 2 MAC CE message is used to indicate to the wireless device the activation of one or more candidate cells in the candidate cell list for the wireless device; and the layer 1 DCI message is used to trigger the serving cell change procedure.

[0009] In any of the above implementations, the method may further include: in response to receiving the fast serving cell change signaling, executing, by the wireless device, a serving cell change operation set for a serving cell change procedure to a target serving cell.

[0010] In any of the above implementations, the serving cell change operation set may include key code verification.

[0011] In any of the above implementations, the key code verification may include: when the key code received in the fast serving cell change signaling matches the value of the verification key code in the RRC configuration, notifying the upper layer of the serving cell change process, otherwise ignoring the fast serving cell change signaling.

[0012] In any of the above implementations, the serving cell change operation set may include: determining whether to perform a RACH process to access a target serving cell as part of a serving cell change process based on fast serving cell change signaling; and in response to determining that the RACH process is to be performed, continuing to perform the RACH process.

[0013] In any of the above implementations, the serving cell change operation set may include: determining whether to perform a RACH process to access a target serving cell as part of a serving cell change process based on fast serving cell change signaling; and in response to determining that the RACH process is to be performed, continuing to perform the RACH process.

[0014] In any of the above implementations, determining whether to perform a RACH procedure may include: in response to receiving fast serving cell change signaling, determining whether the RACH procedure is to be performed.

[0015] In any of the above implementations, determining whether to perform a RACH procedure may include determining whether the RACH procedure is to be performed in response to receiving fast serving cell change signaling and in addition in response to an explicit or implicit RACH indication.

[0016] In any of the above implementations, the explicit RACH indication may include at least one of the following: an explicit RACH process indication in a pre-stored RRC reconfiguration message associated with the target serving cell; the existence of a RACH configuration associated with the target serving cell; or an explicit RACH trigger indication in layer 1 or layer 2 signaling.

[0017] In any of the above implementations, the implicit RACH indication may include at least one of the following: the time advance (TA) value associated with the target serving cell is invalid; there is no TA value or time advance group ID (TAGID) associated with the target serving cell; there is no TA value in the fast serving cell change signaling; or a MAC reset is performed.

[0018] In any of the above implementations, parameters associated with the RACH procedure may be preconfigured in an RRC configuration associated with the target serving cell; and the RACH procedure includes a contention-free RACH (CFRA) procedure or a contention-based RACH (CBRA) procedure.

[0019] In any of the above implementations, the method may also include, as part of the RACH procedure, when a RACH preamble identifier and / or a RACH opportunity (RO) identifier is provided by the wireless communication node via layer 1 signaling or layer 2 signaling or RRC signaling, determining that a CFRA procedure is followed and using the RACH preamble identifier and the RO identifier for the CFRA procedure; and when no RACH preamble identifier or a RACH RO identifier is signaled or the RACH preamble identifier is equal to 0x000000, determining that a CBRA procedure is followed and selecting a target SSB having a synchronization signal-RSRP (SSB-RSRP) higher than a reference signal received power threshold and a RACH preamble corresponding to the target SSB from multiple signal blocks (SSBs) to perform the CBRA procedure.

[0020] In any of the above implementations, the serving cell change operation set may include determining whether a normal full MAC reset or an adapted MAC reset is to be performed, the adapted MAC reset being adapted for a fast serving cell change.

[0021] In any of the above implementations, whether a normal full MAC reset or an adapted MAC reset will be performed can be determined by: an explicit RRC information unit in the RRC configuration associated with the target service cell or a target service cell list including the target service cell, which explicit RRC information unit indicates whether a normal full MAC reset or an adapted MAC reset is performed; or an explicit indication in the fast service cell change signaling, which explicit indication indicates whether a normal full MAC reset or an adapted MAC reset is performed.

[0022] In any of the above implementations, the adaptive MAC reset may include one or more of the following: canceling the ongoing RACH process; clearing the RACH message 3 cache; clearing the RACH message A cache; canceling the triggered beam failure recovery (BFR) process on the target service cell; canceling the triggered power headroom report (PHR) process on the target service cell; canceling the triggered persistent listen-before-talk (LBT) failure for the original cell and the target service cell of the wireless device; resetting the beam failure instance BFI counter (BFI-COUNTER) for the original cell and the target service cell of the wireless device; resetting the LBT_COUNTER for the original cell and the target service cell of the wireless device; canceling the triggered scheduling request (SR) process; clearing the soft cache of all downlink hybrid automatic repeat request (DL HARQ) processes for the original cell, and treating the next received transmission of the transport block (TB) as the first transmission; or setting the new data indicator (NDI) for all UL HARQ process IDs for the source service cell and the target service cell to zero.

[0023] In any of the above implementations, the serving cell change operation set may include serving cell activation or deactivation.

[0024] In any of the above implementations, the serving cell deactivation may include: deactivating all active SCells of a master cell group (MCG) in response to a PCell change; or deactivating all SCells of a secondary cell group (SCG) in response to a SpCell change.

[0025] In any of the above implementations, whether to trigger serving cell deactivation may be indicated in fast serving cell change signaling.

[0026] In any of the above implementations, the serving cell deactivation may be performed on all active serving cells that are not included in the RRC information element in the RRC configuration associated with the target serving cell.

[0027] In any of the above implementations, the serving cell change operation set may include reestablishing a radio link control (RLC) entity; and whether the RLC entity will be reestablished is indicated by: an information element in the RRC configuration associated with the target serving cell, or an indication in the fast serving cell change signaling.

[0028] In any of the above implementations, the serving cell change operation set may include a Packet Data Convergence Protocol (PDCP) duplication process.

[0029] In any of the above implementations, the method may further include: when a signal radio bearer (SRB) is configured with carrier aggregation (CA) duplication, suspending PDCP duplication for the SRB until a serving cell change procedure is completed.

[0030] In any of the above implementations, the method may also include: when there are only two RLC entities associated with PDCP replication for one data radio bearer (DRB), automatically deactivating PDCP replication when fast service cell change signaling is received regardless of whether it is on the MCG or SCG; and when there are more than two RLC entities associated with PDCP replication for one DRB, when fast service cell change signaling is received regardless of whether it is on the MCG or SCG, deactivating RLC entities other than the master RLC entity used for PDCP replication.

[0031] In any of the above implementations, the method may also include: when there are more than two RLC entities associated with PDCP replication and belong to different cell groups, and when the primary path is located in the MCG, when fast service cell change signaling is received on the SCG, deactivating PDCP replication for all RLC entities in the SCG.

[0032] In any of the above implementations, the method may also include: in response to receiving fast serving cell change signaling, performing an RRC reconfiguration process according to a first field in a pre-stored RRC reconfiguration message associated with the target serving cell to implement a serving cell change process.

[0033] In any of the above implementations, the method may also include storing one or more of the cell group configuration, C-RNTI, public service cell configuration, or dedicated service cell configuration associated with the source service cell in a pre-stored RRC reconfiguration message in a cell configuration list under the cell ID corresponding to the target service cell.

[0034] In any of the above implementations, the method may also include: in response to receiving a fast service cell change signaling: in response to determining from the RRC configuration of the target service cell indicated by the fast service cell change signaling that the target service cell is a SCell in the pre-configured SCell list, performing at least one of the following: configuring the SCell according to the differential configuration of the target service cell; activating the SCell when the SCell has not yet been activated; releasing the service cell configuration and notifying the lower layer to release the resources of the current service cell; treating the SCell as a service cell by treating the service cell ID of the SCell as equal to 0; resetting or partially resetting the MAC entity of the service cell group associated with the SCell; or applying a new identifier as the C-RNTI for the service cell group; and in response to determining from the RRC configuration of the target service cell indicated by the fast service cell change signaling that the target service cell is not a SCell in the pre-configured SCell list, performing at least one of the following: configuring the lower layer for the target service cell according to the public service cell configuration; configuring the lower layer for the target service cell according to the dedicated service cell configuration; resetting or partially resetting the MAC entity of the service cell group; or applying a new identifier as the C-RNTI for the cell group.

[0035] In any of the above implementations, the method may also include: the wireless device performs a service cell change operation set of the service cell change process to the target service cell, and then sends a notification to the target service cell using one of the following message formats: MAC CE; uplink control information (UCI) message; RRC message; or RACH is initiated.

[0036] In any of the above implementations, the MAC CE may include one of the following: C-RNTI MAC CE; Buffer Status Report (BSR) MAC CE; or a special MAC CE, which includes indent information and / or a key code of the wireless device, which is specified in the RRC configuration of the target service cell or received from Layer 1 or Layer 2 service cell change signaling.

[0037] In any of the above implementations, the method may also include determining whether an acknowledgement (ACK) or a negative acknowledgement (NACK) for the notification is received from the target serving cell.

[0038] In any of the above implementations, the wireless device determines that an ACK is received when: a RACH process has been successfully executed; a DCI for a new C-RNTI has been received; a MAC CE has been received; or an uplink grant for a new transmission has been received, whose corresponding HARQ process ID is used to send the notification.

[0039] In any of the above implementations, the method may further include: determining that a NACK is received when a timer has expired and no ACK has been received, wherein the timer is configured in the configuration of the target serving cell for determining whether the serving cell change procedure is successful.

[0040] In any of the above implementations, when NACK is determined to be received, the method may further include at least one of the following: triggering an RRC reestablishment process; or restoring to a source serving cell when the current cell configuration has not been released and / or has been stored.

[0041] In some other embodiments, a wireless device including a processor and a memory is disclosed. The processor may be configured to read computer code from the memory to implement any of the above methods.

[0042] In some other embodiments, a computer program product is disclosed, the computer program product comprising a non-transitory computer-readable program medium having computer code stored thereon. The computer code, when executed by a processor, can enable the processor to implement any of the above methods.

[0043] The above-described embodiments and other aspects and alternatives of their implementations will be described in more detail in the following figures, descriptions and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 An example wireless communication network including a radio access network, a core network, and a data network is shown.

[0045] Figure 2 An example wireless access network is shown that includes a plurality of mobile stations or UEs and wireless access network nodes that communicate with each other via an over-the-air radio communication interface.

[0046] Figure 3 An exemplary communication protocol stack in a wireless access network node or a wireless terminal device is shown, including various network layers.

[0047] Figure 4 A split architecture for separating a radio access network node into a central unit (CU) and one or more distributed units (DUs) is shown.

[0048] Figure 5 An example signaling and operational flow diagram for the preparation phase of a lower layer fast serving cell change is shown.

[0049] Figure 6 An example signaling and operational flow diagram for the execution phase of a lower layer fast serving cell change is shown. DETAILED DESCRIPTION

[0050] Examples of the techniques and implementations and / or embodiments described in the present disclosure may be used to facilitate radio resource allocation, configuration, and signaling in wireless access networks. The term "exemplary" is used to mean "example" and does not mean an ideal or preferred example, implementation, or embodiment unless otherwise specified. Section titles are used in the present disclosure to facilitate understanding of the disclosed implementations and are not intended to limit the techniques disclosed in this section to the corresponding sections. The disclosed implementations may also be embodied in a variety of different forms, and therefore, the scope of the present disclosure or the claimed subject matter is intended to be interpreted as not being limited to any embodiment described below. Various implementations may be embodied as methods, devices, components, systems, or non-transitory computer-readable media. Therefore, the embodiments of the present disclosure may, for example, take the form of hardware, software, firmware, or any combination thereof.

[0051] The present disclosure relates to UE measurements and measurement reporting of serving cells, and configurations for cell measurements and reporting to enable fast serving cell changes during UE mobility within lower network layers, such as layer 1 or layer 2 of a wireless communication protocol stack. The present disclosure also relates to signaling procedures associated with fast serving cell changes for UEs as triggered by the network based on cell measurements and reporting, and various lower layer configurations and operations for implementing the actual fast serving cell changes at and for the UE.

[0052] Wireless Network Overview

[0053] An example wireless communication network, such as Figure 1 As shown in Figure 100, user equipment (UE) 110, 111 and 112, operator network 102, various service applications 140 and other data networks 150 may be included. Operator network 102 may include, for example, access networks 120 and 121 and core network 130. Operator network 110 may be configured to send voice, data and other information (collectively referred to as data traffic) between UE 110, 111 and 112, between UE and service application 140, or between UE and other data networks 150. Access networks 120 and 121 may be configured as various wireless access network nodes (WANN, alternatively referred to as base stations) to interact with UE on one side of a communication session and core network 130 on the other side. Core network 130 may include various network nodes configured to control communication sessions and perform network access management and traffic routing. Service application 140 may be hosted by various application servers deployed outside core network 130 but connected to core network 130. Likewise, other data networks 150 may also be connected to the core network 130 .

[0054] exist Figure 1In the wireless communication network 100 of FIG. 1 , UEs may communicate with each other via a wireless access network. For example, UEs 110 and 112 may be connected to the same access network 120 and communicate via the same access network 120. UEs may communicate with each other via both an access network and a core network. For example, UE 110 may be connected to access network 120, and UE 111 may be connected to access network 121, and thus, UE 110 and UE 111 may communicate with each other via access networks 120 and 121 and core network 130. UEs may also communicate with service applications 140 and data network 150 via core network 130. In addition, UEs may also communicate directly with each other via side link communications, as shown by 113.

[0055] Figure 2 Also shown is an example system diagram of a wireless access network 120, which includes a WANN 202 serving UEs 110 and 112 via an air interface 204. The wireless transmission resources used for the air interface 204 include a combination of frequency, time and / or space resources. Each of the UEs 110 and 112 can be a mobile or fixed terminal device installed with a mobile access unit (such as a SIM / USIM module for accessing the wireless communication network 100). Each of the UEs 110 and 112 can be implemented as a terminal device, including but not limited to a mobile phone, a smart phone, a tablet computer, a laptop computer, an in-vehicle communication device, a roadside communication device, a sensor device, a smart home appliance (such as a TV, a refrigerator, and an oven), or other devices capable of wireless communication over a network. As Figure 2 As shown, each of the UEs (such as UE 112) may include a transceiver circuit system 206 coupled to one or more antennas 208 to enable wireless communication with WANN 120 or with another UE (such as UE 110). Transceiver circuit system 206 may also be coupled to processor 210, which may also be coupled to memory 212 or other storage device. Memory 212 may be transient or non-transitory and may store computer instructions or codes therein that, when read and executed by processor 210, cause processor 210 to implement the various methods described herein.

[0056] Similarly, WANN 120 may include a base station or other wireless network access point that is capable of wirelessly communicating with one or more UEs via air interface 204 and communicating with core network 130. For example, WANN 120 may be implemented in the form of a 2G base station, a 3G Node B, an LTE eNB, a 4G LTE base station, a 5G NR base station, a 5G central unit base station, or a 5G distributed unit base station, but is not limited thereto. Each type of these WANNs may be configured to perform a corresponding set of wireless network functions. WANN 202 may include a transceiver circuit system 214 that is coupled to one or more antennas 216, which may include various forms of antenna towers 218 to enable wireless communications with UEs 110 and 112. Transceiver circuit system 214 may be coupled to one or more processors 220, which may also be coupled to a memory 222 or other storage device. The memory 222 may be transient or non-transitory and may store therein instructions or codes that, when read and executed by the one or more processors 220 , cause the one or more processors 220 to implement various functions of the WANN 120 described herein.

[0057] Data packets in wireless access networks (such as Figure 2 The data included therein may be packaged as PDUs in various network layers and wrapped with nested and / or layered protocol headers. Once a connection (e.g., a radio link control (RRC) connection) is established between a transmitting device or a transmitting end (these two terms are used interchangeably) and a receiving device or a receiving end (these two terms are also used interchangeably), the PDUs may be transmitted between the transmitting end and the receiving end. Either the transmitting device or the receiving device may be a wireless terminal device (such as a wireless terminal device). Figure 2 devices 110 and 120 in the wireless access network) or wireless access network nodes such as Figure 2 Each device may be both a sending device and a receiving device for bidirectional communication.

[0058] like Figure 3 As shown, WANN 120 may also include multiple separate access network nodes, in the form of a central unit (CU) 302 and at least one distributed unit (DU) 304 and 306. CU 122 may be connected to DU1 304 and DU2 306 via various F1 interfaces. The F1 interface may also include, for example, an F1-C interface and an F1-U interface, which may be used to carry control plane data and user plane data, respectively. The UE may be connected to the core network 130 via the WANN 120 via a radio interface.

[0059] Each DU can serve UEs via one or more cells. Each cell is associated with a coverage area. These cells may alternatively be referred to as serving cells. The coverage areas between cells may partially overlap. Each UE may actively communicate with at least one cell and may potentially be connected or connectable to more than one cell. Figure 3 In the example of , UE1, UE2, and UE3 can be served by cell 1 320 of DU1, while UE4 and UE5 are served by cell 2 330 of DU1. In some implementations, the UE can be served by two or more cells at the same time. Each UE can be mobile, and the signal strength and quality from each cell at the UE can depend on the UE location. In some embodiments, the CU can be a gNB central unit (gNB-CU) and the DU can be a gNB distributed unit (gNB-DU). Although the various implementations described below are provided in the context of a 5G cellular wireless network, the basic principles described herein are applicable to other types of radio access networks, including but not limited to other generations of cellular networks as well as Wi-Fi, Bluetooth, ZigBee, and WiMax networks.

[0060] In some example implementations, Figure 3 The cells shown in may alternatively be referred to as serving cells. The serving cells may be grouped into serving cell groups (CGs). The serving cell group may be a main CG (MCG) or a secondary CG (SCG). In each type of cell group, there may be one main cell and one or more secondary cells. For example, the main cell in an MSG may be referred to as a PCell, and the main cell in an SCG may be referred to as a PScell. The secondary cells in either an MCG or an SCG may be referred to as SCells. The main cells including PCells and PScells may be collectively referred to as SpCells. All these cells may be referred to as serving cells or cells. Unless otherwise specifically distinguished, the terms "cell" and "serving cell" may be used interchangeably in a general manner. The term "serving cell" may refer to a cell that is serving, will serve, or may serve a UE. In other words, a "serving cell" may not currently serve a UE. Although the various embodiments described below may sometimes relate to one of the above-mentioned serving cell types, the basic principles apply to all types of serving cells in both types of serving cell groups.

[0061] Figure 4 It is further shown that Figures 1 to 3 4, a simplified view of various network layers involved in sending a user plane PDU from a sending device 402 to a receiving device 404 in an example wireless access network of FIG. 4. Figure 4 It is not intended to include all necessary device components or network layers for handling the transmission of PDUs. Figure 4The data packetized by the upper network layer 420 at the sending device 402 can be transmitted via the packet data convergence protocol layer (PDCP layer, Figure 4 The PDUs are transmitted to the corresponding upper layers 430 (such as the radio resource control or RRC layer) at the receiving device 304 by the physical (PHY) layer and radio interface (shown as 406) of the transmitting and receiving devices, and the medium access control (MAC) layer 434 and RLC layer 432 of the receiving device. The respective network entities in each of these layers may be configured to handle the transmission and retransmission of the PDUs.

[0062] exist Figure 4 The upper layer 420 may be referred to as layer 3 or L3, while the intermediate layers (such as the RLC layer and / or the MAC layer and / or the PDCP layer ( Figure 4 The layers 1 and 2 of the physical layer 1 may be collectively referred to as layer 2 or L2, and the term layer 1 is used to refer to layers associated with the physical layer and the radio interface. In some cases, the term "low layer" may be used to refer to the set of L1 and L2, while the term "high layer" may be used to refer to layer 3. The term "lower layer" may be used to refer to layers in L1, L2, and L3 that are lower than the current reference layer. Control signaling may be initiated and triggered in each of L1 to L3 and in each of the network layers therein. These signaling messages may be encapsulated and concatenated into packets of the lower layers and sent via allocated control or data air radio resources and interfaces. The term "layer" generally includes its various corresponding entities. For example, the MAC layer includes corresponding MAC entities that may be created. For example, layer 1 includes a PHY entity. Another example is that layer 2 includes a MAC layer / entity, an RLC layer / entity, and / or a PDCP layer / entity.

[0063] Back to Figure 3 , various functions of the radio access network node can be split between the CU and the DU. For example, the DU can host the lower layers including the L2 and L1 layers, such as the RLC, MAC, and PHY (physical) layers, while the CU can host the higher layers of the network, such as the L3.

[0064] General UE mobility and serving cell change

[0065] As the UE moves between the coverage areas of various cells, the signal level and quality from the cells change. The UE can be configured to measure and monitor the cell signal level and quality. The parameters associated with performing these measurements can be configured by the network. At some point, the signal difference between the cells may require a service cell change (alternatively referred to as a service cell switch, PCell and SCell role change, or service cell switch) from the source service cell (alternatively referred to as the original service cell) to the target service cell to actively serve the UE. The source service cell and the target (service) cell can be served by the same DU, or by different DUs associated with the same CU, or by different CUs. Therefore, the service cell change can be intra-DU (when changing cells within one or more cells served by the same DU) or inter-DU (when changing from a source cell served by one DU to a target cell served by another DU). Inter-DU service cell changes can be intra-CU (when changing from a source cell to a target cell served by the same CU) or inter-CU (when changing from a source cell served by one CU to a target cell served by another CU). These cell changes represent different levels of cell changes and may involve various levels of serving cell change configuration, reset and handover procedures.

[0066] In some implementations, regardless of whether the source and target serving cells are inter-CU or intra-CU, serving cell switching may be triggered due to L3 measurements and may be implemented through radio resource control (RRC) signaling with synchronization. For example, RRC signaling may be used to implement the change of SpCell (from one SpCell to another SpCell) (SpCell can be PCell or PSCell), and the release / addition of SCell when applicable. Such SpCell change procedures initiated via RRC reconfiguration usually cause long interruptions of user plane data communications / flows, significant delays in updating user plane data transmission, and are usually associated with considerable RRC signaling overhead.

[0067] Sometimes, such a high latency serving cell change procedure from one serving cell to another based on RRC reconfiguration may be difficult to avoid, especially when the change involves source and target serving cells served by different CUs (inter-CU serving cell change). However, in most cases, the handover may occur from one cell to another served by the same DU (intra-DU serving cell change), or between cells served by different DUs of the same CU (inter-DU but intra-CU). In these cases, the UE serving cell change may not require any change involving the serving CU hosting the L3 entity. In this case, the UE mobility only necessarily involves the non-L3 lower layers in the communication protocol stack residing in the DU, including, for example, layers of L1 and / or L2, such as the RLC / MAC / PHY layers, as Figure 3 In this case, there is no need to require the UE to perform a serving cell change procedure based on L3 signaling.

[0068] The service cell change process implemented only by L1 and / or L2 signaling is fast / flexible, has minimal impact / interruption on user plane data flow, and helps to reduce switching delay and signaling overhead. This L1 / L2-based service cell change can be referred to as a fast service cell change, and the change process can be correspondingly referred to as a fast cell change process or a fast service cell change process. A hyphen ("-") can be added between the words in these terms without changing their meaning. In a cellular network where DU switching occurs frequently during UE mobility, for example, when the carrier frequency of the air radio band only supplies a short communication range and dense cells are required, the cumulative reduction in communication delay and signaling overhead will be very significant.

[0069] The disclosure herein provides various example implementations of mobility measurement / reporting and its configuration and signaling, serving cell change signaling, cell change procedures, and data communication updates due to cell changes in the context of fast cell changes that rely on low-level signaling and operations. Such procedures can provide fast, efficient, and low-latency cell changes with minimal user plane data flow interruption, and can be based on L1 / L2 UE mobility.

[0070] Overall fast inter-cell mobility based on L1 / L2

[0071] In general, UE mobility can be achieved by monitoring the signal levels from various cells during UE movement, reporting cell measurements to the network, performing a service cell change process when certain cell switching conditions are met, and performing various processes for updating the current communication session. Each element of the access network, including the UE and the WANN (or base station, referred to as NW in this article, representing the network side) collaborates to complete the entire mobility process. For example, the base station can be responsible for providing various configurations related to UE mobility, while the UE can be responsible for various cell measurements and reports. The base station, rather than the UE, can ultimately determine whether to perform a service cell change and whether to trigger a cell switch in order to balance the UE load served by both the source service cell and the target service cell. For example, the target service cell can be determined by the NW based on a cell measurement report from the UE and notified with a signal. In certain implementations of L1 / L2 center fast mobility, such as traditional L3-based mobility, the actions on the UE side during the mobility process can be divided into two stages:

[0072] ● Preparation phase: includes L1 and / or L3 measurements on various cells and reporting the measurements from the UE to the NW.

[0073] ●Execution phase: includes the behavior of UE / NW at each network layer when receiving L1 / L2 signaling for mobility, including PHY layer (L1), MAC layer, RLC layer, PDCP (L2) and RRC (L3) layer, as well as the evaluation of the service cell change result, and the execution of corresponding UE / NW operations after the service cell change.

[0074] For the preparation phase of L1 / L2 based fast mobility - general

[0075] Example UE and NW (e.g., base station) interactions during the preparation phase associated with the fast serving cell change procedure Figure 5 In such an example preparation phase, the general process may include but is not limited to:

[0076] ●Step 1: NW configures cell measurement configuration and cell measurement reporting configuration to UE.

[0077] ●Step 2: The UE performs cell measurement according to the received cell measurement configuration, and determines whether to trigger reporting of the measurement results to the NW based on the cell measurement reporting configuration, such as pre-configured reporting conditions (for example, time-triggered conditions, such as periodic, semi-persistent periodic reporting, or event-triggered conditions, as described in further detail below).

[0078] ● Step 3: If the cell measurement reporting condition is met, the UE reports the cell measurement results related to the source cell and one or more candidate cells adjacent to the source cell to the NW.

[0079] Preparation for L1 / L2-based fast mobility - cell measurement configuration and cell measurement

[0080] Cell measurements may be of different types, including but not limited to L3 measurements and / or L1 measurements. The measurement objects within the serving cell may include characteristics that can be used to determine the signal quality and channel state of the cell, including but not limited to synchronization system blocks (SSBs), channel state information reference signals (CSI-RSs), etc. The reporting timing modes include periodic, aperiodic, semi-static periodic, or at moments triggered by predefined or configured events. The communication resources used to send cell measurement reports may include, for example, physical uplink control channel (PUCCH) resources and / or physical uplink shared channel (PUSCH) resources (in time and frequency).

[0081] For example, measurements may be performed in the L1 layer of SSB and / or CSI-RS. L1 measurements may include:

[0082] ● Perform L1 measurements on the source cell currently providing active service to the UE.

[0083] ● Perform L1 measurement on one or more neighbor cells of the source cell.

[0084] In some implementations, the cell measurement configuration and the cell measurement reporting configuration may be signaled separately from the NW. In some other implementations, these configurations may be signaled to the UE as an integral signaling message. These configurations may specify the measurements to be performed, the content to be reported, the format for reporting, reporting timing, reporting trigger conditions, reporting transmission resource allocation, etc.

[0085] For example, the cell measurement configuration and (multiple) cell measurement reporting configurations may indicate the following, such as various CSI measurements:

[0086] ●CSI-MeasConfig, specifies the set of CSI measurement and reporting configurations for the following CSI

[0087] ■CSI-ResourceConfig (e.g., periodic, aperiodic, semi-persistent periodic reporting configuration).

[0088] ■ NZP-CSI-RS-ResourceSet (ie, the set of non-zero power CIS-RS resources to be measured in, for example, a periodic, aperiodic or semi-persistent periodic manner).

[0089] ■ CSI-RS-SSB-ResourceSet (ie, the CSI-RS-SSB resource set to be measured in, for example, a periodic, aperiodic or semi-persistent periodic manner).

[0090] ■ CSI-ReportConfig (ie, report trigger configuration for reporting cell measurements in a periodic, aperiodic or semi-persistent periodic manner over time or when an event is triggered).

[0091] The above example cell measurement and cell measurement report configurations may be specified per cell. For example, the source cell and the neighboring cell may be provided with different cell measurement and cell measurement report configurations. The neighboring cells to be measured may be configured as a list of candidate neighboring cells for the source cell for the cell change. The candidate cell list may be predetermined as a result of the cell configuration in the area, or may be signaled from the network. For the above example implementations, both / one of the NZP-CSI-RS-ResourceSet and / or CSI-RS-SSB-ResourceSet may be associated with a cell indicated by PhysicalCellID or additionalPCIIndex.

[0092] Preparation for L1 / L2-based fast mobility - Cell measurement report

[0093] In some implementations, the signaling and messaging of the cell measurement report may be performed in the L1 and / or L2 layers instead of the L3 layer. The layer(s) from which the cell measurement report is sent may be predefined, preconfigured, or dynamically configured from the NW. In some example implementations, the signaling / transmission of the cell measurement report may be specified as part of the cell measurement report configuration described above. For example, the cell measurement report may be signaled / sent via:

[0094] L1 signaling and messaging (eg, via uplink signaling, such as uplink control information (UCI), which may be transmitted over PUCCH or PUSCH); and / or

[0095] - L2 signaling and messaging (eg, via MAC CE for reporting cell measurements for serving cell change procedure).

[0096] For the above L1 or L2 signaling / messaging, the measurement results that may be included in the cell measurement report may also be predefined or preconfigured, for example, configured in a manner specified in the above cell measurement report configuration. The following may be signaled as optional or alternative content that may be included in the cell measurement report:

[0097] 1. Direct measurement results of the source serving cell and one or more neighboring cells of the source serving cell, for example, which may include at least one of the following information:

[0098] ① direct measurement results of one or more neighboring cells as potential target cells for cell change,

[0099] ② Direct measurement results of the source serving cell; or

[0100] 2. Identification and related information of one or more neighboring cells of the current source serving cell suitable for handover, including, for example:

[0101] ① Physical Cell Information (PCI), used to indicate one or more neighboring physical cells determined by the UE to be suitable as target cells for serving cell change,

[0102] ② Optionally, additional beam information for indicating (multiple) physical cells is used to indicate beams of (multiple) suitable adjacent physical cells that are suitable as serving beams for serving cell change.

[0103] The first alternative described above may be particularly suitable for L1 signaling / messaging for reporting of L1 cell measurements, since the L1 measurements may be directly included in the L1 measurement report message without involving other higher layers. By reporting direct measurements via L1 or L2 signaling / messaging, a decision to determine and identify a target serving cell for a serving cell change may be made by the NW based on the direct measurements as reported in the cell measurement report and other factors known to the NW. The direct measurement results for the source cell or one or more neighboring cells may include overall measurements of neighboring cells and various beams within each neighboring cell.

[0104] Regarding the second alternative, the selection of suitable neighboring cells for fast serving cell change can be performed by the UE based on direct cell measurements performed at layer 1 in the UE. The selection can be performed, for example, in a set of candidate cells that are predetermined, preconfigured, or signaled from the NW, as described above. One or more such suitable neighboring cells can be selected and reported. After receiving the selection, the NW can further determine the target serving cell for fast serving cell change.

[0105] Further, with respect to the second alternative described above, physical cell information for any suitable neighboring cells and beam information for any suitable beams may be included in the cell measurement report. Such information may include, but is not limited to:

[0106] ● Physical cell information of suitable neighboring cells, for example, including at least one of the following:

[0107] ○ Physical cell identification

[0108] ○ The position or index of the suitable cell in the candidate cell list (for example, 0 represents the first cell information in the candidate cell information list, 1 represents the second cell information in the candidate cell information list, and so on);

[0109] Beam information for the indicated suitable physical cell, including, for example, at least one of the following:

[0110] ○ the CSI-RS ID and / or SSB identifier associated with the beam,

[0111] ○ The beam position or index associated with the candidate beam list for the physical cell (ie, 0 represents the first beam in the candidate beam list, 1 represents the second beam in the candidate beam list, and so on).

[0112] In some implementations for L1 signaling / message transmission, such physical cell and beam information may be reported via code points. In some other implementations, the physical cell information and beam information may be indicated by one or more bitmaps used for L1 or L2 signaling / message transmission. For example, a physical cell bitmap may be included in a cell measurement report to indicate one or more suitable neighboring cells in a set of candidate cells for a serving cell change. Further, within a suitable physical cell, a beam bitmap may be included in a cell measurement report to indicate one or more beams of a physical cell deemed by the UE to be suitable for a serving cell change. Other ways of indicating the above-mentioned physical cell information and beam information besides code points or bitmaps may also be implemented in a cell measurement report.

[0113] In some other example implementations, the cell measurement report may include a combination of the above two alternatives. Specifically, the cell measurement report, transmitted via L1 or L2 signaling / message, may include direct measurement results of one or more suitable neighboring cells or beams selected by the UE from candidate cells or beams for serving cell change.

[0114] Preparation for L1 / L2-based fast mobility - Cell measurement reporting via trigger event conditions

[0115] In some implementations, cell measurements may be reported to the NW according to a predefined or preconfigured timing. For example, cell measurements may be periodically reported at a preconfigured time slot.

[0116] In some other example implementations, the cell measurement report may be sent according to one or more triggering events. Whether the cell measurement report is sent according to time or triggering events may be preconfigured, such as indicated in the cell measurement report configuration described above.

[0117] Regarding event-based cell measurement reporting, for example, the cell measurement reporting may be triggered at L1 or L2 by satisfying one or more of the following event conditions:

[0118] 1: The measurement results of the source serving cell meet the following formulated conditions (called the bad serving cell rule (BSC)):

[0119] The measurement result of the source cell ≤ threshold 1 + offset 1 (1)

[0120] and / or

[0121] 2: The measurement result of at least one of the candidate neighboring target cells satisfies the following formulated condition (called the Good Target Cell Criteria (GTC)):

[0122] The measurement result of the candidate target cell ≥ threshold 2 + offset 2 (2)

[0123] Meeting the above BSC conditions implies that the source serving cell may not be suitable for serving the UE and a serving cell change may be required. Meeting the above GTC conditions implies that at least one neighboring serving cell may be suitable as a potential target cell for switching to. The above "Threshold1" represents a baseline cell signal quality threshold for determining whether the source serving cell has become unsuitable for supporting a communication link, and "Offset2" represents a tolerance level for Threshold1. Similarly, the above "Threshold2" represents a baseline cell signal quality threshold for determining whether a neighboring cell is suitable as a potential target serving cell for a serving cell change, and "Offset2" represents a tolerance level for Threshold2. Each of "Threshold1", "Threshold2", "Offset1" and "Offset2" may be predetermined, preconfigured or dynamically configured. In some example implementations, the baseline threshold may be predefined and the tolerance level may be configured.

[0124] In some cases, especially when the UE is at the cell edge or border, the relative signal between the current source serving cell and one or more neighboring cells may fluctuate greatly. Therefore, the mechanism for determining whether the current source serving cell is bad and whether at least one neighboring cell is good based on the above mechanism may cause frequent serving cell changes as a result of the ping-pong effect. The ping-pong effect may cause serious inefficiency and communication overhead. In order to avoid or reduce the ping-pong effect on L1 / L2 mobility, and considering the limitations of computing and signal processing capabilities in the L1 / L2 layer, the following enhanced mechanism can be adopted by the UE to trigger the transmission of cell measurement results to the NW based on events:

[0125] ●BSC condition: N consecutive measurement results of the source serving cell satisfy the condition of formula (1) above, and / or

[0126] ●GTC condition: while or after the source serving cell is measured, M consecutive measurement results of at least one neighboring cell meet the condition of the above formula (2).

[0127] In another specific implementation for avoiding or reducing the ping-pong effect, another enhancement mechanism may be adopted by the UE to trigger the transmission of the cell measurement result to the NW based on an event.

[0128] ●BSC condition: the average measurement result of N consecutive measurement results of the source serving cell satisfies the condition of the above formula (1), and / or

[0129] ●GTC condition: the average measurement result of M consecutive measurement results of at least one neighboring cell satisfies the condition of the above formula (2).

[0130] In some example implementations, the measurement results of the source serving cell or the neighboring cell may be cell level measurement results or beam level measurement results. The cell level measurement results may be obtained, for example, from the measurement results of one or more beams. The beam level measurement results may include, for example, a predetermined or preconfigured optimal beam number P for a specific cell. In the above implementations, M, N, and P may be predefined, preconfigured, or dynamically configured positive integers.

[0131] The N consecutive source cell measurements and the M consecutive neighbor cell measurements correspond to the source cell measurement time window and the neighbor cell measurement time window, respectively. The enhancement mechanism represents a filtering process that smoothes the consecutive measurements to more accurately represent the channel quality of each cell to avoid or reduce the ping-pong effect.

[0132] In some example implementations, the measurement results may include one or more of a reference signal received power (RSRP), a signal to interference and noise ratio (SINR), a reference signal received quality (RSRQ) level, etc., as a reflection of the channel state. When more than one result is used, the results may be aggregated or combined (e.g., averaged, weighted averaged, etc.), and correspondingly, the baseline thresholds and offset values ​​in the above formulas (1) and (2) may also be aggregated or combined. Alternatively, each of the multiple measurement results for a cell may be associated with its own threshold and offset, thereby providing sub-conditions based on formulas (1) and (2). Each of these formulas may be deemed to be satisfied when, for example, all or most of the sub-conditions are satisfied.

[0133] As an example for the above implementation, when it is detected that the number of consecutive measurements indicating a bad source cell is equal to or greater than N, and / or when it is detected that the number of consecutive measurements indicating that at least one candidate neighboring cell is a good target cell is equal to or greater than M, the MAC layer may generate and / or send a MAC CE or notify the L1 layer to send an L1 message to report the cell measurement results to the NW. Therefore, the MAC layer may be configured to track the number of BSC and GTC measurements by using simple logic and counters, thereby not requiring the MAC layer to have complex calculation capabilities.

[0134] In some simple logic and counter implementations, the MAC layer or entity may maintain one or two counters, referred to as COUNTER A and COUNTER B. COUNTER A may be incremented by 1 by the MAC layer or entity when an indication about BSC is received from a lower layer, and COUNTER B may be incremented by 1 by the MAC layer or entity when an indication about GTC is received from a lower layer. In such an implementation, one or two timers may be maintained in the MAC layer, referred to as Timer A and Timer B, respectively. Timer A may be associated with COUNTER A, and / or Timer B may be associated with COUNTER B. When COUNTER A is being incremented, Timer A may be started or restarted, and when COUNTER B is being incremented, Timer B may be started or restarted. When Timer A expires, COUNTER A may be reset to 0, and when Timer B expires, COUNTER B may be reset to 0. In addition, one or two maximum values ​​M and / or N for COUNTER A and COUNTER B may be preconfigured to trigger or send a cell measurement report. When COUNTER A and / or COUNTER B reaches a maximum value M and / or N, a cell measurement report may be triggered and / or sent.

[0135] As an example for the above implementation, when notified by the L1 layer to send a MAC CE, the MAC layer may generate and / or send a MAC CE, or when the L1 layer detects that an average value greater than or equal to N consecutive measurement results indicates a bad source cell condition, and / or when the L1 layer detects that an average value greater than or equal to M consecutive measurement results indicates that at least one candidate neighboring cell is a good target cell, the L1 layer may send an L1 message to report the cell measurement result to the NW. Therefore, the MAC layer may be configured to track indications from lower layers regarding BSC and GTC information to generate and send a MAC CE for a cell measurement report. Therefore, when an indication for BSC and / or GTC information is received from a lower layer, the MAC layer may trigger and / or send a cell measurement report.

[0136] In some other implementations, the event triggering condition may be based on a combination of a source cell measurement result (referred to as a "first cell measurement result") and one or more neighboring cell measurement results (referred to as a "second cell measurement result"). For example, a differential result between the first cell measurement result and the second cell measurement result may be used as a basis for a triggering event for reporting cell measurement. Specifically, an example of a triggering event condition may be expressed as:

[0137] The result of the neighboring cell - the result of the source cell ≥ Threshold3 + Offset3, (3)

[0138] The definition or configuration of “Threshold3” and “Offset3” may be similar to the definition or configuration of the above-mentioned “Threshold1”, “Threshold2”, “Offset1” and “Offset2”.

[0139] In order to avoid or reduce the ping-pong effect on L1 / L2 mobility and taking into account the limited L1 / L2 computing power, the above differential measurement can be performed continuously within the measurement window, and when X consecutive different measurements meet the conditions in the above formula (3), the cell measurement report can be triggered. In a more detailed description of this implementation, a counter (referred to as COUNTER C) and a timer (referred to as Timer C) can be introduced at the L2 layer. For example, COUNTER C can be associated with Timer C, and when the MAC layer receives an indication from the lower layer that formula (3) is satisfied, COUNTER C is incremented by 1. Timer C can be started or restarted as long as COUNTER C is incremented by 1. When Timer C times out, COUNTER C can be reset to 0. In addition, a maximum value X can be preconfigured, and when COUNTER C reaches the maximum value X, the L2 layer can generate and / or send a cell measurement report, and / or when COUNTER C reaches the maximum value X, the L2 layer can instruct the lower layer to generate and / or send a cell measurement report.

[0140] In another implementation for avoiding or reducing the ping-pong effect on L1 / L2 mobility, considering the limited L1 / L2 computing power, the measurement result of the neighboring cell may be the average of Y consecutive measurements of the neighboring cell, and the measurement result of the source cell may be the average of Y consecutive measurements of the source serving cell. In a more detailed description of this implementation, when an indication satisfying formula (3) is received from a lower layer, the L2 layer may trigger and / or generate a cell measurement report, and / or when the difference satisfies formula (3), the L1 layer may trigger and / or generate a cell measurement report.

[0141] Again, the measurement reflected in the above formula (3) can be a cell-level differential measurement result or a beam-level differential measurement result. The cell-level differential measurement result can be obtained from the differential measurement results of one or more beams. For example, the beam-level measurement result may include a predetermined or preconfigured optimal number of beams P for a particular cell. The differential measurement result may be a differential RSRP, SINR, RSRQ, and / or other differential characteristics reflecting the channel state of the measured cell.

[0142] In various implementations of the above event-triggered cell measurement report, the triggering event related to the neighboring cell may be configured per candidate neighboring cell, per candidate neighboring cell list, or per cell group.

[0143] The triggering events for different candidate cells, different candidate cell lists or different candidate cell groups may be configured differently. For example, each candidate cell, each candidate cell list or each candidate cell group may be independently configured with its corresponding triggering event. For example, one neighboring candidate cell may be associated with a triggering event based on formulas (1) and (2) with filtering, while another neighboring candidate cell may be associated with a triggering event based on formula (3) with filtering, or vice versa. Then, any neighboring cell that satisfies its corresponding triggering event will cause a cell measurement report to be sent.

[0144] In some other implementations, one or more of the following events may also trigger a cell measurement report:

[0145] ● BF (beam failure) on the source serving cell is detected, and less than P suitable beams of the source serving cell can be identified, P being a predetermined, configured positive integer, and / or

[0146] • Radio link failure with respect to the source serving cell is detected.

[0147] Meeting these conditions implies that the source serving cell no longer supports communications and a cell handover is required, and the triggered cell measurement report will serve to prompt the NW to provide and specify a target serving cell for the serving cell change, regardless of the quality of the target cell.

[0148] Execution Phase - General

[0149] In some implementations, once the cell measurements are reported, the NW may determine whether a fast serving cell change should be performed for the reporting UE based on the reported cell measurements. If the decision is to proceed with the fast serving cell change, the NW may determine the target serving cell and may begin the execution phase of the fast serving cell change.

[0150] Example steps for the execution phase of a fast serving cell change are Figure 6 As shown. Figure 6 As shown, these steps may include:

[0151] Step 1: The source cell sends an L1 and / or L2 signaling message to the UE to trigger the fast serving cell change procedure.

[0152] Step 2: The UE performs a fast serving cell change operation set.

[0153] Step 3: The UE notifies the target serving cell of the fast serving cell change.

[0154] Step 4: The target serving cell confirms the UE notification.

[0155] Step 5: If the fast serving cell change fails according to the response or no response from the target serving cell in step 4, the UE performs additional operations.

[0156] L1 / L2 signaling for triggering fast serving cell change

[0157] The fast serving cell change may be triggered by the source serving cell based on L1 / L2 signaling / message delivery. For example, the trigger may be based entirely on L1 signaling / message delivery, such as via (multiple) downlink control information (DCI) messages. In such an example implementation, the L1 trigger DCI message may include at least one of a set of information items, including but not limited to:

[0158] ●Target service cell information:

[0159] ○ Physical Cell ID (PCI): indicates the target serving cell to which the UE should transfer;

[0160] ○ Serving cell ID: indicates the target serving cell to which the UE should transfer; or

[0161] ○ Candidate cell ID: Indicates the target serving cell to which the UE should transfer.

[0162] ● Beam information: For example, indicating which transmission configuration indicator (TCI) state can be activated for uplink and / or downlink after the UE transfers to the target serving cell. In some implementations, the beam indication can be based on the CSI-RSID and / or SSB ID. In some implementations, the beam indication can be indicated via the TCI state ID. In some implementations, the transmission reception point (TRP) indication can be indicated via the TRP position within the TRP list.

[0163] ● Timing Advance (TA) information: indicates the TA value of the indicated target serving cell.

[0164] ● Preamble Index: Indicates the preamble index used for the UE to perform RACH on the indicated target serving cell.

[0165] ● RO Index: Indicates the RACH opportunity (RO) index for the UE to perform RACH on the indicated target serving cell.

[0166] ●Cell Radio Network Temporary Identifier (C-RNTI): used to indicate a new C-RNTI to the UE when transferring to a target serving cell.

[0167] ● KeyCode: used by UE to verify L1 signaling from NW (source serving cell). It may also be included in the RRC configuration of the indicated target serving cell indicated by the physical cell information.

[0168] In some other example implementations, the triggering of the fast serving cell change procedure by the source serving cell may be based entirely on L2 signaling / message transmission, such as via one or more MAC CEs. In such example implementations, the L2 triggering MAC CE may include at least one of a set of information items similar to the information items listed above for the L1 triggering DCI.

[0169] In some other example implementations, L1 DCI and L2 MAC CE may be used jointly to trigger a fast serving cell change process. For example, one or more MAC CEs may be used to activate one or more candidate cells in a candidate cell list to achieve a fast serving cell change. Such a MAC CE may be sent to one or more candidate cells for activation. The MAC CE may also be sent to the UE as part of a trigger to indicate to the UE which candidate serving cells are activated for a fast serving cell change. In addition, one or more DCIs may be used to actually trigger a fast serving cell change to a specific target serving cell among those candidate serving cells activated by one or more MAC CEs. In one implementation, the MAC CE used to activate a candidate serving cell for a fast serving cell change may include at least one of the following information:

[0170] ● Target serving cell information, which may be indicated by a physical cell identity, which may be indicated by an index of a candidate serving cell in a candidate target serving cell list.

[0171] ●Beam information: beam information associated with each target serving cell information presented in the same MAC CE, which can be indicated by SSB information and / or CSI-RS information, and / or TCI status identification.

[0172] UE fast serving cell change operation - general

[0173] The following describes an example set of fast serving cell change operations that a UE may perform in response to receiving L1 or L2 fast serving cell change signaling or triggering.

[0174] For example, the L2 layer of the UE may perform at least one of the following:

[0175] ●Keycode verification (verify) to verify the fast serving cell change signaling.

[0176] ● One or more Random Access Channel (RACH) procedures to access the target serving cell.

[0177] • One or more full MAC layer resets or adapted MAC layer resets.

[0178] ● One or more serving cells activation / deactivation operations

[0179] For another example, one or more RLC layer operations may also be performed in the UE. In addition, one or more PDCP layer operations may be performed in the UE. In addition, one or more RRC layer operations may be performed in the UE.

[0180] These example operations of the UE in various network layers in response to fast serving cell change signaling are described in more detail below.

[0181] UE fast serving cell change operation - MAC layer

[0182] In some implementations, after receiving fast service cell change signaling from the source service cell, the UE may first perform a key verification for the fast service cell change. In some example implementations, if the key in the received L1 / L2 signaling for the fast service cell change matches the value of the reference key in the RRC configuration associated with the target service cell and / or source service cell for the fast service cell change, the UE may determine that the key verification is successful. The UE may then proceed to notify the upper layer of the fast service cell change. Otherwise, the UE may ignore the received L1 / L2 fast service cell change signaling without performing further service cell change operations.

[0183] After successful verification, the UE may, for example, perform one or more RACH procedures to access the target serving cell. For example, the RACH procedure may involve first determining by the UE whether any RACH operation needs to be performed. More specifically, the UE may determine whether to perform a RACH procedure to access the target serving cell as part of the serving cell change procedure based on the fast serving cell change signaling, and in response to determining that the RACH procedure is to be performed, continue to perform the RACH procedure.

[0184] In some example implementations, as long as L1 / L2 signaling for fast serving cell change is received and successfully verified via the keying procedure described above, RACH operation may be initiated on the target serving cell.

[0185] In some alternative implementations, when L1 / L2 signaling for fast serving cell change is received, whether RACH operation on the target serving cell should be initiated may be determined by one or more of the following explicit indications:

[0186] ● An explicit RACH procedure indication pre-stored in an RRC reconfiguration message associated with the target serving cell. For example, there may be an information element in the RRC reconfiguration message indicating whether a RACH procedure is required.

[0187] • There is a RACH configuration associated with the target serving cell.

[0188] • Explicit RACH triggering indication in layer 1 or layer 2 signaling for fast serving cell change.

[0189] If one or more of the above explicit conditions are met, RACH operation may be performed.

[0190] In some other alternative implementations, when L1 / L2 signaling for fast serving cell change is received, whether RACH operation on the target serving cell should be initiated may be determined by one or more of the following implicit indications:

[0191] • The Timing Advance (TA) value associated with the target serving cell is invalid.

[0192] • There is no TA value or timing advance group (TAG) ID associated with the target serving cell.

[0193] ●There is no TA value in the fast serving cell change signaling.

[0194] ●MAC reset is performed.

[0195] If one or more of the above implicit conditions are met, RACH operation may be performed.

[0196] In some example implementations, once the UE determines that a RACH procedure is to be performed on the target serving cell, it may proceed to perform the RACH operation. Various parameters for the RACH operation may be preconfigured in the RRC configuration associated with the target serving cell. Additionally, the RACH procedure may be a contention-free RACH (CFRA) procedure or a contention-based RACH (CBRA) procedure.

[0197] In some example implementations, when a RACH preamble identifier and / or a RACH opportunity (RO) identifier is provided by the NW via layer 1 signaling or layer 2 signaling for fast serving cell change or RRC signaling, the UE may determine that a CFRA procedure is to be followed and may continue to perform the CFRA procedure using the RACH preamble identifier and RO identifier explicitly provided by the NW.

[0198] In some example implementations, when no RACH preamble identifier or a RACH RO identifier is signaled, or a presented RACH preamble identifier is equal to 0b000000 or a dedicated RRC configuration is not signaled, the UE may determine that a CBRA procedure is to be followed and may proceed to select a target SSB among a plurality of signal blocks (SSBs) to perform the CBRA procedure, the selected target SSB having a synchronization signal-RSRP (SS-RSRP) above a reference signal received power threshold and a RACH preamble corresponding to the target SSB.

[0199] In some example implementations, a normal full MAC reset or an adapted MAC reset may be performed. For example, the UE may first determine whether a full or adapted MAC reset is to be performed. For example, an explicit RRC information element in an RRC configuration associated with a target serving cell or a target serving cell list including the target serving cell may indicate to the UE whether to perform a normal full MAC reset or an adapted MAC reset. For another example, an explicit indication in fast serving cell change signaling may indicate to the UE whether to perform a normal full MAC reset or an adapted MAC reset.

[0200] In some implementations, the adapted MAC reset may include performing one or more of the following:

[0201] ●Cancel the ongoing RACH process;

[0202] ● Clear the RACH message 3 cache;

[0203] ● Clear the RACH message A buffer;

[0204] ●Cancel the triggered beam failure recovery (BFR) procedure on the target serving cell;

[0205] ● Cancel the triggered Power Headroom Report (PHR) procedure on the target cell;

[0206] ● canceling a triggered persistent listen-before-talk (LBT) failure for the wireless device's origin cell and target serving cell;

[0207] ● Reset the beam failure instance BFI counter (BFI-COUNTER) for the wireless device's original cell and target serving cell;

[0208] ● Reset the LBT_COUNTER for the wireless device's original cell and target serving cell;

[0209] ●Cancel the triggered Scheduling Request (SR) process;

[0210] ● flush the soft buffers of all downlink hybrid automatic repeat request (DL HARQ) processes for the original cell and treat the next received transmission of the transport block (TB) as the first transmission; or

[0211] • Set the New Data Indicator (NDI) to zero for all UL HARQ Process IDs for both the original cell and the target cell.

[0212] In some implementations, the adaptive MAC reset may be a subset of a normal full MAC reset. In some implementations, some operations within the adaptive MAC reset may be modified from the corresponding normal MAC reset operations. In some implementations, the main difference between a full MAC reset and an adaptive MAC reset may be that a full MAC reset includes considering all TA timers as expired for all time advance groups (TAGs), while an adaptive MAC reset may not include such considerations. Some example modifications and adaptations for fast serving cell change are reflected in the list above for an adapted MAC reset.

[0213] In some implementations, the AllowedServingCell for an LCH (e.g., DRB mapping to a serving cell) may be determined. In one implementation, if an LCH has been configured with an allowedServingCell containing a target cell, and the target cell is the only cell, and if the target cell is one of the SCells, the UE may regard the serving cell with ID=0 as the allowedServingCell. In one implementation, the AllowedServingCell for the LCH MAC CE may be introduced to dynamically adjust the allowedServingCell for one or more LCHs. In another implementation, the MAC CE may include at least one of the following information:

[0214] ●LCH ID: Indicates the LCH used for remapping to the serving cell.

[0215] ● Serving cell ID: Indicates the serving cell to which the LCH should be mapped.

[0216] In one implementation, it is up to the NW to adjust the allowed serving cells for the LCH via RRC reconfiguration before sending the L1 / L2 signal for the serving cell change or after the serving cell change is sent to the UE.

[0217] In some implementations, in response to receiving fast service cell change signaling, the UE's MAC layer operations may also include service cell activation and deactivation operations. The UE may determine whether to perform any service cell deactivation based on an indication that may be included in the fast service cell change signaling. For example, when L1 / L2 fast service cell change signaling is received and verified, the UE may deactivate all activated service cells (such as SCells) of the cell group associated with the MAC entity. For example, the UE may deactivate all SCells for the MCG in the case of a PCell change, or deactivate all SCells for the SCG in the case of a PSCell change. In some example implementations, the UE may deactivate all activated SCells that are not included in the service cell list indicated by the RRC information element in the RRC configuration associated with the target service cell or the candidate target service cell list.

[0218] UE fast serving cell change operation - RLC layer

[0219] In some implementations, when L1 / L2 fast serving cell change signaling is received and verified, the UE may perform one or more RLC layer operations. For example, the RLC layer operation may include reestablishing the RLC entity. In some implementations, whether the RLC entity is to be reestablished may be indicated by an information element in the RRC configuration associated with the target serving cell or an indication (such as a flag indicator) in the fast serving cell change signaling. In some implementations, such an indication information element may be for the RLC entity of the cell group involved. In some other implementations, the indication information element may be configured per cell group.

[0220] UE fast serving cell change operation - PDCP layer

[0221] In some implementations, when L1 / L2 fast serving cell change signaling is received and verified, the UE may perform one or more PDCP layer operations.

[0222] In some implementations, when a signal radio bearer (SRB) is configured with carrier aggregation (CA) duplication, the UE may suspend PDCP duplication for the SRB until the serving cell change procedure is completed. In such an implementation, the PDCP entity may generate only one PDCP PDU and send it to the lower layers of the primary path.

[0223] In some implementations, when there are only two RLC entities associated with PDCP duplication for one data radio bearer (DRB), the UE may automatically deactivate PDCP duplication when fast serving cell change signaling is received on either the MCG or SCG.

[0224] In some other implementations, when there are more than two RLC entities associated with PDCP duplication for one DRB, the UE may deactivate RLC entities other than the primary RLC entity for PDCP duplication when fast serving cell change signaling is received on either the MCG or SCG.

[0225] In another example implementation, in a case where there are more than two RLC entities associated with PDCP duplication and the RLC entities belong to different CGs, if the primary path is located in the MCG and if L1 / L2 signaling for fast serving cell change is received for the SCG, the UE may deactivate PDCP duplication for all RLC entities in the SCG. In another implementation, in a case where there are more than two RLC entities associated with PDCP duplication and the RLC entities belong to different CGs, if the primary path is located in the SCG and if L1 / L2 signaling for fast serving cell change is received for the MCG, the UE may deactivate PDCP duplication for all RLC entities in the MCG.

[0226] In some implementations, PDCP recovery may be performed by the UE. For example, an information element may be included in an RRC configuration associated with a target cell and / or a candidate target cell list. The information element may be used to indicate to the UE whether the UE needs to perform PDCP recovery for acknowledged mode (AM) DRBs. If indicated, the UE may proceed with performing such PDCP recovery for AM DRBs.

[0227] UE fast serving cell change operation - RRC layer

[0228] In some example implementations, when L1 / L2 fast serving cell change signaling is received and verified, the UE may perform one or more RRC layer operations. The RRC layer operations may depend on various RRC models. Two example RRC models, and corresponding RRC layer operations that the UE may perform under each RRC model, are described below.

[0229] RRC Model #1

[0230] In the example RRC model #1, the fast serving cell change based on L1 / L2 signaling can continue to use the pre-configured RRCReconfiguration message to implement the fast serving cell change. More specifically, the UE can still follow the normal behavior of the RRC reconfiguration process, such as reusing the information element reconfigurationWithSync to implement the fast serving cell change.

[0231] In some implementations, the NW may pre-configure the UE with an L1L2CentricRRCReconfig including an RRCReconfiguration message. The UE may then store the L1L2CentricRRCReconfig information in a UE variable for fast serving cell change based on L1 / L2 signaling. An example RRC structure is shown in Table 1 below. In some example implementations, a key code may be configured for fast serving cell change in such an example RRC structure.

[0232] Table 1

[0233]

[0234] As shown in Table 1, the RRC element reoconfigurationWithSync2 may be introduced in the information element of CellGroupConfig which may be mutually exclusive with reconfigurationWithSync.

[0235] In some implementations, if ReconfigurewithSync is received / configured in an RRCReconfiguration message for fast serving cell change, the MAC layer may be completely reset in a normal manner and the TA values ​​for all TAGs may be considered invalid. In contrast, if ReconfigurewithSync2 is received / configured in an RRCReconfiguration message for fast serving cell change, the MAC layer may be adaptively reset as described above, and if the corresponding TA timer has not expired, the TA value for the MAC entity may still be considered valid.

[0236] In some implementations of ReconfigurationWithSync2, the following information elements may also be included:

[0237] SCellID / ServingCellID / AssistanceCellID / CandidateCellID / PhysicalCellID: Indicates the target cell for fast serving cell change. In one implementation, the UE may apply the cell configuration associated with this information element (ie, ServingCellConfigComm and / or ServingCellConfig) as the serving cell configuration for fast serving cell change.

[0238] ●ServingCellConfigCommon: as a cell-specific parameter for the target serving cell.

[0239] ●ServingCellConfig: as a UE-specific parameter for the target serving cell.

[0240] ● New UE-ID: Indicates the new C-RNTI that should be used after a fast serving cell change. If not present, the old C-RNTI should be retained to be used when transferring to the target serving cell.

[0241] Utilizing RRC Model #1, in some example implementations, the UE may store the current CellGroupConfiguration and / or C-RNTI and / or servingCellConfigCommon and / or servingCellConfigDedicated into a list of candidate target cells, where the minimized L1L2CentricRRCReconfigID is currently available when an indication for a fast serving cell change is received from lower layers.

[0242] In some other implementations, the UE may store the current CellGroupConfiguration and / or C-RNTI and / or servingCellConfigCommon and / or servingCellConfigDedicated into a candidate target cell list, where sameL1L2CentricRRCReconfigID belongs to the target serving cell indicated by the L1 / L2 signaling for fast serving cell change.

[0243] Therefore, the following example steps may be performed by the UE under RRC Model #1:

[0244] ●Step 1: The UE may determine whether an indication of a fast serving cell change from a lower layer is received, and if so, proceed to step 2, otherwise, proceed to the end.

[0245] ●STEP 2: The UE may perform an RRCReconfiguration procedure according to the RRCReconfiguration message of the target serving cell stored in the L1L2CentricRRCReconfigToADDmodList indicated by the indication from the lower layer, and then proceed to STEP 3.

[0246] ●STEP 3: The UE stores the current CellGroupConfiguration and / or C-RNTI and / or servingCellConfigCommon and / or servingCellConfigDedicated in the RRCReconfiguration message of the source serving cell in L1L2CentricRRCReconfigToADDmodList together with the sameL1L2CentricRRCReconfigID of the target serving cell.

[0247] In another example implementation, the following steps may be performed by the UE under RRC Model #1:

[0248] ● Step 1: The UE may determine whether reconfigurationWithSync2 or reconfigurationWithSync is included in the RRC reconfiguration message. If reconfigurationWithSync is included, go to step 2A, otherwise, go to step 2B.

[0249] • Step 2A: The UE may perform RRC reconfiguration for fast serving cell change as normal (ie, normal full MAC reset) and then go to End.

[0250] • Step 2B: The UE may perform RRC reconfiguration for fast serving cell change with adapted reset of MAC entity. Then go to End.

[0251] RRC Model #2

[0252] In example RRC model #2, candidate target serving cell configurations for fast serving cell change may be located in one or more cell configuration lists, which may be configured in the cell group configuration CellGroupConfig and / or the cell configuration SpCellConfig.

[0253] In some example implementations, if the target serving cell is one of the SCells, the UE may apply the delta reconfiguration of the target serving cell in the list for fast serving cell change. For such implementations, the deltaConfigurationForSpCellChange information element may include at least one of the following information:

[0254] ●PUCCH channel related configuration.

[0255] ●NewUEIdentity.

[0256] ●Radio link monitoring related configuration.

[0257] ●Beam failure recovery related configuration.

[0258] RACH related configuration, including:

[0259] ■RACH resource configuration.

[0260] ■Dedicated RACH resource configuration.

[0261] ●ResetMAC / PartialResetMAC flag.

[0262] ●Timer for fast serving cell change.

[0263] ●KeyCode.

[0264] In some example implementations, if the target serving cell is not one of the SCells in SCellToAddModlist, the UE may apply the RRC configuration of the target serving cell for fast serving cell change. In other words, the target serving cell cannot be activated as an SCell, and the RRC configuration of the target serving cell may include at least one of the following information:

[0265] ●ServingCellConfigCommon: Indicates cell-specific parameters for the target serving cell.

[0266] ●ServingCellConfigDedicated: Indicates UE-dedicated parameters for the target serving cell.

[0267] RACH related configuration: Indicates the RACH resources / parameters of the target serving cell, including at least one of the following:

[0268] ■RACH resource configuration.

[0269] ■Dedicated RACH resource configuration.

[0270] ● Timer for fast serving cell change: A timer used by the UE to determine whether the fast serving cell change is successfully terminated.

[0271] ●NewUEIdentity: C-RNTI that should be used after a fast serving cell change.

[0272] ●ResetMAC: Indicates whether the MAC entity should be reset.

[0273] ●TAG ID: Indicates the TAG to which the target serving cell belongs.

[0274] ●KeyCode.

[0275] Therefore, the following example steps may be performed by the UE under RRC Model #2:

[0276] • Step 1: The UE may determine whether an indication of a fast serving cell change is received from a lower layer, and if so, go to step 2. Otherwise, go to the end.

[0277] ●Step 2: The UE may determine whether the RRC configuration of the target serving cell indicated by the L1 / L2 signaling from the lower layer is an SCell in the SCellToAddmodList, if yes, proceed to step 3, if not, proceed to step 4.

[0278] ●Step 3: The UE may adapt at least one of the following operations and then proceed to the end.

[0279] ■Configure the SCell based on the differential configuration of the target serving cell.

[0280] ■ If the SCell is not activated yet, activate the SCell.

[0281] ■ Release the serving cell configuration and notify lower layers to release the resources of the current serving cell.

[0282] ■ The SCell is considered as the serving cell. In one implementation, the serving cell ID of the SCell is considered equal to 0.

[0283] ■ Reset or adaptively reset (e.g., partially reset) the MAC entity of this cell group

[0284] ■ If present, ueNewIdentity is applied as the C-RNTI for this cell group.

[0285] ●Step 4: The UE may adjust at least one of the following operations and then terminate.

[0286] ■ If present, the lower layers for the target serving cell are configured according to ServingCellConfigCommon.

[0287] ■ If present, the lower layers used for the target serving cell are configured according to ServigCellConfigDedicated.

[0288] ■ Reset or adaptively reset (eg, partially reset) the MAC entity of this cell group.

[0289] ■ If present, ueNewIdentity is applied as the C-RNTI for the cell group.

[0290] Notification to target serving cell

[0291] After the UE performs the above-mentioned various fast serving cell change operations, it may send a notification of completion of the fast serving cell change operation to the target serving cell. For example, such a notification may be sent in at least one of the following formats:

[0292] MAC CE notification, including one of the following:

[0293] ■C-RNTI MAC CE.

[0294] ■BSR MAC CE.

[0295] ■NEW MAC CE, which may contain information of the UE identity and / or key configured in the RRC configuration associated with the target serving cell / candidate target serving cell list / source cell or / and in the L1 / L2 signaling for triggering a fast serving cell change.

[0296] ●UCI, such as scheduling request.

[0297] ●RRC message.

[0298] ●RACH process.

[0299] In some implementations involving MAC CEs, if no available PUSCH can be used to transmit them, a Scheduling Request (SR) should be triggered.

[0300] Response to notification from target serving cell

[0301] The response to the above notification from the target serving cell may include an acknowledgement (ACK), or a negative acknowledgement (NACK), or no response.

[0302] In some implementations, if a RACH procedure has been performed for L1 / L2 signaling based on a fast serving cell change, successful termination of the RACH procedure may be considered as an ACK indication.

[0303] In some implementations, the receipt of the DCI for the new C-RNTI may be considered an ACK indication.

[0304] In some implementations, the reception of a MAC CE may be considered as an ACK indication. In this implementation, the MAC CE may include only a subheader without any payload, or the MAC CE may include at least one of the following information:

[0305] KeyCode; or

[0306] ●New C-RNTI.

[0307] In some implementations, when a UL grant for a new transmission is received, where the HARQ process ID is used to send a notification to the NW, the ACK indication may be considered received.

[0308] In some implementations, a timer (FastServingCellChangeTimer) configured in the configuration associated with the target serving cell and / or the candidate target serving cell list and / or the source serving cell may be used to determine whether the L1 / L2 signaling based on the fast serving cell change is successful. For example, if no ACK is received before the FastServingCellChangeTimer expires, a NACK indication may be considered to be received.

[0309] UE Actions in Case of NACK for Notification

[0310] If the UE determines that NACK is indicated from the target serving cell, the UE may, for example, trigger an RRC reestablishment procedure.For another example, if the source serving cell configuration is not released and / or is stored and still available, the UE may revert to the source serving cell.

[0311] The above description and accompanying drawings provide specific exemplary embodiments and implementations. However, the described subject matter may be embodied in a variety of different forms, and therefore, the subject matter covered or claimed is intended to be interpreted as not being limited to any exemplary embodiment described herein. It is intended to be used for a fairly broad range of the subject matter claimed or covered. Among other things, for example, the subject matter may be embodied as a method, device, component, system, or non-transitory computer-readable medium for storing computer code. Therefore, the embodiment may, for example, take the form of hardware, software, firmware, storage media, or any combination thereof. For example, the above method embodiment may be implemented by a component, device, or system including a memory and a processor by executing a computer code stored in a memory.

[0312] Throughout the specification and claims, terms may have nuanced meanings that are suggested or implied by the context beyond the explicitly stated meanings. Likewise, the phrases "in one embodiment / implementation" used herein do not necessarily refer to the same embodiment, and the phrases "in another embodiment / implementation" used herein do not necessarily refer to a different embodiment. For example, the claimed subject matter is intended to include combinations of all or part of the example embodiments.

[0313] In general, terms can be understood at least in part according to the use in the context. For example, terms such as "and", "or" or "and / or" used in this article may include multiple meanings, which may depend at least in part on the context in which these terms are used. Generally, if "or" is used for an association list (such as A, B or C), it is intended to represent A, B and C (herein with an inclusive meaning) and A, B or C (herein with an exclusive meaning). In addition, the term "one or more" used in this article depends at least in part on the context and can be used to describe any feature, structure or characteristic in a singular sense, or can be used to describe a combination of features, structures or characteristics in a plural sense. Similarly, the terms "a", "an" or "the" can be understood to convey singular usage or to convey plural usage, depending at least in part on the context. In addition, the term "based on" can be understood to not necessarily be intended to convey an exclusive set of factors, but can allow the presence of additional factors that are not necessarily explicitly described, which also depends at least in part on the context.

[0314] References to features, advantages, or similar language throughout this specification do not imply that all features and advantages that may be achieved using the present solution should be included or included in any single implementation thereof. Rather, language referencing features and advantages should be understood to mean that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present solution. Thus, discussions of features and advantages and similar language in this specification may, but do not necessarily, refer to the same embodiment.

[0315] In addition, the features, advantages and characteristics of the present solution can be combined in one or more embodiments in any suitable manner. Based on the description herein, one of ordinary skill in the relevant art will recognize that the present solution can be practiced without one or more specific features or advantages of a particular embodiment. In other cases, additional features and advantages can be identified in certain embodiments, which may not be present in all embodiments of the present solution.

Claims

1. A method for a serving cell change procedure performed by a wireless device, the method comprising: receiving L1 / L2 triggered mobility signaling sent by a wireless communication node in response to a cell measurement report from the wireless device; as well as The serving cell change procedure is triggered in the wireless device from a source serving cell of the wireless device to a target serving cell, the serving cell change procedure comprising: a serving cell change operation set performed in layer 1 and layer 2.

2. The method according to claim 1, wherein the L1 / L2 triggered mobility signaling comprises a layer 2 MAC CE, and the layer 2 MAC CE comprises at least one of the following: identification information of the target serving cell; beam information indicating which transmission configuration indicator (TCI) state can be activated for uplink and / or downlink communication after the serving cell change procedure; timing advance (TA) information associated with time alignment between the wireless device and the target serving cell; a preamble index of a RACH preamble used by the wireless device to perform random access to the target serving cell; or A RACH opportunity (RO) index is provided for the wireless device to perform the random access to the target serving cell.

3. The method according to claim 1, further comprising: In response to receiving the L1 / L2 triggered mobility signaling, the serving cell change operation set for the serving cell change procedure to the target serving cell is performed by the wireless device.

4. The method according to claim 1, further comprising: If at least one of the following conditions is met, in response to receiving the L1 / L2 triggered mobility signaling, a RACH procedure is initiated to access the target serving cell: a timing advance (TA) value associated with the target serving cell is invalid; The TA value or timing advance group ID (TAGID) associated with the target serving cell does not exist; The TA value does not exist in the L1 / L2 triggered mobility signaling; or A MAC reset is performed.

5. The method of claim 1 , wherein the method further comprises initiating a RACH procedure, and as part of the RACH procedure: In case a RACH preamble identifier and / or a RACH opportunity (RO) identifier is provided by the wireless communication node via layer 2 signaling, determining that a contention-free RACH (CFRA) procedure is followed, and using the RACH preamble identifier and the RO identifier for the CFRA procedure.

6. The method according to claim 1, further comprising: In response to receiving the L1 / L2 triggered mobility signaling, an RRC reconfiguration procedure is performed according to a first field in a pre-stored RRC reconfiguration message associated with the target serving cell to implement the serving cell change procedure.

7. The method according to claim 1, further comprising: After the serving cell changes the operation set, the wireless device sends an RRC notification message to the target serving cell.

8. The method of claim 7, wherein the wireless device determines that an ACK is received based on at least one of the following conditions: The RACH procedure has been successfully performed; DCI for the new C-RNTI has been received; or An uplink grant for a new transmission has been received, and its corresponding HARQ process ID is used to send the RRC notification.

9. The method according to claim 8, further comprising: A NACK is determined to be received if a timer has expired and no ACK has been received, the timer being configured in the target serving cell for determining whether the serving cell change procedure is successful.

10. The method according to claim 9, in the case where the NACK is determined to be received, the method further comprises at least one of the following: Trigger the RRC re-establishment process; or In the case that the current cell configuration has not been released and / or has been stored, the source serving cell is restored.

11. A wireless device comprising a processor and a memory, wherein the processor is configured to read computer code from the memory to cause the wireless device to: receiving L1 / L2 triggered mobility signaling sent by a wireless communication node in response to a cell measurement report; and triggering, in the wireless device, a serving cell change procedure from a source serving cell of the wireless device to a target serving cell, the serving cell change procedure comprising: A set of serving cell change operations performed within Layer 1 and Layer 2.

12. The wireless device of claim 11, wherein the L1 / L2 triggered mobility signaling comprises a layer 2 MAC CE, the layer 2 MAC CE comprising at least one of the following: identification information of the target serving cell; beam information indicating which transmission configuration indicator (TCI) state can be activated for uplink and / or downlink communication after the serving cell change procedure; timing advance (TA) information associated with time alignment between the wireless device and the target serving cell; a preamble index of a RACH preamble used by the wireless device to perform random access to the target serving cell; or A RACH opportunity (RO) index is provided for the wireless device to perform the random access to the target serving cell.

13. The wireless device of claim 11, wherein the computer code, when executed by a processor of the wireless device, further causes the wireless device to: initiate a RACH procedure to access the target serving cell in response to receiving the L1 / L2 triggered mobility signaling if at least one of the following conditions is satisfied: a timing advance (TA) value associated with the target serving cell is invalid; The TA value or timing advance group ID (TAGID) associated with the target serving cell does not exist; The TA value does not exist in the L1 / L2 triggered mobility signaling; or A MAC reset is performed.

14. The wireless device of claim 11, wherein the computer code, when executed by a processor of the wireless device, further causes the wireless device to: initiate a RACH procedure, and as part of the RACH procedure: In case a RACH preamble identifier and / or a RACH opportunity (RO) identifier is provided by the wireless communication node via layer 2 signaling, determining that a contention-free RACH (CFRA) procedure is followed, and using the RACH preamble identifier and the RO identifier for the CFRA procedure.

15. The wireless device of claim 11, wherein the computer code, when executed by a processor of the wireless device, further causes the wireless device to: after a serving cell changes an operation set, send, by the wireless device, an RRC notification message to the target serving cell.

16. The wireless device of claim 11, wherein the computer code, when executed by a processor of the wireless device, further causes the wireless device to determine that an ACK is received based on at least one of the following conditions: The RACH procedure has been successfully performed; DCI for the new C-RNTI has been received; or An uplink grant for a new transmission has been received, and its corresponding HARQ process ID is used to send the RRC notification.

17. The wireless device of claim 11, wherein the computer code, when executed by a processor of the wireless device, further causes the wireless device to: in response to receiving the L1 / L2 triggered mobility signaling, execute the serving cell change operation set for the serving cell change procedure to the target serving cell.

18. A computer program product comprising a non-transitory computer readable program medium having computer code stored thereon, the computer code, when executed by a processor of a wireless device, causing the wireless device to: receiving L1 / L2 triggered mobility signaling sent by a wireless communication node in response to a cell measurement report; and triggering, in the wireless device, a serving cell change procedure from a source serving cell of the wireless device to a target serving cell, the serving cell change procedure comprising: A set of serving cell change operations performed within Layer 1 and Layer 2.

19. The computer program product of claim 18, wherein the L1 / L2 triggered mobility signaling comprises a layer 2 MAC CE, the layer 2 MAC CE comprising at least one of: identification information of the target serving cell; beam information indicating which transmission configuration indicator (TCI) state can be activated for uplink and / or downlink communication after the serving cell change procedure; timing advance (TA) information associated with time alignment between the wireless device and the target serving cell; a preamble index of a RACH preamble used by the wireless device to perform random access to the target serving cell; or A RACH opportunity (RO) index is provided for the wireless device to perform the random access to the target serving cell.

20. The computer program product of claim 18, wherein the computer code, when executed by the processor of the wireless device, causes the wireless device to: in response to receiving the L1 / L2 triggered mobility signaling, perform the serving cell change operation set for the serving cell change procedure to the target serving cell.

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