Layer 1 or 2 mobility in wireless communication systems

Abstract

Various exemplary embodiments relate to wireless communication systems, and more particularly to facilitating mobility within such wireless communication systems. Aspects and embodiments relate to at least user equipment of a radio access network and methods performed by the user equipment. According to one aspect, the user equipment comprises at least one processor and at least one memory that stores instructions that, when executed by the at least one processor, cause the user equipment to at least: determine that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; receive reference signal configurations associated with reference signals receivable from one or more network nodes of a radio access network, where the configurations may include configurations for reference signals receivable from a target network node; receive a mobility trigger indicating that the user equipment should switch to the target network node, where the mobility trigger may include configurations associated with reference signals receivable from the target network node; switch to the target network node; evaluate whether the mobility trigger or the received reference signal configurations include configurations associated with reference signals receivable from the target network node; and, if so, monitor reference signals receivable from the target network node according to the evaluated associated configurations. The configuration recognizes that mechanisms that may be employed for beam management of a serving cell may be less suitable when lower layer triggered mobility is operational. The described embodiments and configurations utilize information provided to the user equipment, such as by a transmission configuration indicator TCI state information, for communication with the target cell without the user equipment needing to have an active TCI state for the target cell before the target cell activates the TCI state.According to some described aspects, the user equipment may not require pre-activation of the TCI state to be applied at the time of handover, i.e., the beam indication does not need to point to a candidate RRC configuration that is not yet active (before the handover). Such embodiments and configurations reduce the implementation requirements of the user equipment and simplify the network signaling required to support mobility events.

Description

[Technical Field]

[0001] Various exemplary embodiments relate to wireless communication systems, and more particularly to facilitating mobility within such wireless communication systems. [Background technology]

[0002] Wireless communication systems are continually evolving and evolving, including providing systems that support multiple transmission and reception points (TRPs) and various antenna configurations at transmitting and receiving nodes within the network.

[0003] As user equipment (UE) moves within a wireless communication system, it may move within areas of radio coverage supported by one or more network access nodes. Maintaining the ability of a UE to communicate effectively with the wireless communication system as it moves within areas of radio coverage is typically referred to as mobility. Network access nodes within a wireless communication network may have different operating characteristics.

[0004] As wireless communication systems develop and evolve, supporting mobility may require some adaptation to wireless communication devices, infrastructure, and signaling. Summary of the Invention

[0005] The scope of protection sought for various exemplary embodiments of the invention is set forth in the independent claims. To the extent that there are exemplary embodiments and features described herein that do not fall within the scope of the independent claims, they should be construed as examples useful for understanding various embodiments of the invention.

[0006] According to various, but not necessarily all, example embodiments, there is provided a user equipment of a radio access network comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to at least: determine that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; receive reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network, where the configurations may include configurations for reference signals receivable from a target network node; receive a mobility trigger indicating that the user equipment should switch to the target network node, where the mobility trigger may include configurations associated with reference signals receivable from the target network node; switch to the target network node; evaluate whether the mobility trigger or the received reference signal configurations include configurations associated with reference signals receivable from the target network node, and if so, monitor reference signals receivable from the target network node in accordance with the evaluated associated configurations.

[0007] According to some embodiments, one of the one or more network nodes is a network node supporting a serving cell to which the user equipment is connected.

[0008] According to some embodiments, the target network node is a network node that supports a target cell or a target candidate cell, which may include a cell to which the user equipment switches from the serving cell.

[0009] According to some embodiments, the network node supporting the serving cell and the network node supporting the target cell or target candidate cell are the same node or different nodes, and both nodes may or may not be physically co-located.

[0010] According to some embodiments, there is provided a user equipment of a radio access network comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to operate and perform the following steps:

[0011] The user equipment may determine that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility. The determination may be based on receiving a configuration message or indication from the network. The configuration may include a Radio Resource Control (RRC) message. The message may be received from the user equipment's serving cell or serving network node.

[0012] The user equipment may receive a reference signal configuration associated with a receivable reference signal from one or more network nodes of a radio access network. The reference signal configuration may be received at the user equipment. The reference signal configuration may be based on receiving a configuration message or an indication from the network. The reference signal configuration may be based on receiving a configuration message or an indication from a serving cell or a serving network node of the user equipment. The receiving may include receiving a radio resource control (RRC) message or a medium access control (MAC) control element (CE). The reference signal configuration may include any suitable indication or mapping of a reference signal configuration. The reference signal configuration may include, for example, a transmission configuration indication (TCI) state, a quasi-colocation (QCL) indication of a reference signal, a direct indication of a reference signal, an inter-cell beam management (ICBM) reference, etc.

[0013] The received configuration may include configurations of reference signals receivable from the target network node. The received configuration may include configurations associated with a serving cell or a network node. The received configuration may include configurations associated with a cell other than the serving cell or the target cell. The configuration may explicitly include reference configurations (e.g., TCI state, QCL, reference signals) associated with the user equipment's serving cell. The configuration may or may not further include explicit reference configurations associated with the target cell and / or implicit reference configurations associated with the target cell. Such implicit references may, for example, be associated in some way with the serving cell configuration.

[0014] The user equipment may receive a mobility trigger indicating that the user equipment switches to a target network node. The mobility trigger may be received at the user equipment. The mobility trigger may be based on receiving a configuration message or an indication from the network. The mobility trigger may be based on receiving a configuration message or an indication from a serving cell or a serving network node of the user equipment. The mobility trigger may be transmitted as part of a MAC CE message transmitted to the UE from a serving network node, i.e., a serving network node supporting the serving cell to which the UE is connected, and may include or support the functionality of a Distributed Unit (DU).

[0015] The mobility trigger may include a configuration associated with a reference signal receivable from the target network node. As mentioned above, the received configuration may include a configuration for a reference signal receivable from the target network node. The received configuration may include a configuration associated with a serving cell or a network node. The received configuration may include a configuration associated with a cell other than the serving cell or the target cell. The configuration may explicitly include reference configurations (e.g., TCI state, QCL, reference signals) associated with the serving cell of the user equipment. The configuration may or may not further include explicit reference configurations associated with the target cell and / or implicit reference configurations associated with the target cell. Such implicit references may, for example, be associated in some way with the serving cell configuration.

[0016] The user equipment may switch to the target network node. The switching may include, for example, a handover from a serving cell to the target cell. The switching may include, for example, the UE performing a random access procedure or the like to perform the handover / switch to the target cell. The switching may occur without the user equipment performing a random access procedure to the target cell. The evaluating may be performed before such a switching step, since the switching may be performed after the evaluating step.

[0017] The user equipment may evaluate whether the mobility trigger or the received reference signal configuration includes a configuration associated with a reference signal receivable from the target network node.

[0018] In response to detecting that the mobility trigger or the received reference signal configuration includes a configuration associated or associable with a reference signal receivable from the target network node, the user equipment may be configured to monitor the reference signal receivable from the target network node in accordance with the detected associated configuration.

[0019] In response to detecting that both the mobility trigger and the received reference signal configuration include a configuration associated or associable with a reference signal receivable from the target network node, the user equipment may select the most recently received configuration, and the user equipment may then be configured to monitor reference signals receivable from the target network node in accordance with the detected associated configuration.

[0020] In response to detecting that neither the mobility trigger nor the received reference signal configuration includes a configuration associated with or associable with a reference signal receivable from the target network node, the user equipment may be configured to perform a random access procedure to the target node.

[0021] The user equipment may be further adapted to assume that, after switching to the target network node, reference signal configurations associated with reference signals receivable from the target network node are unknown.

[0022] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a transmission configuration indicator state, the configuration comprising a transmission configuration indicator state of reference signals receivable from a target network node, and after switching to the target network node, the user equipment is configured to not apply the transmission configuration indicator states of reference signals receivable from the target network node that were received before switching to the target network node.

[0023] According to some embodiments, if the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network include a configuration for reference signals receivable from the target network node, the user equipment is configured to perform monitoring of reference signals receivable from the target network node in accordance with the evaluated associated configurations at least until a mobility trigger is received.

[0024] According to some embodiments, evaluating whether a reference signal or a reference signal configuration associated with a mobility trigger includes a configuration for a reference signal receivable from the target network node comprises selecting a reference signal configuration associated with a reference signal receivable from the target network node received in the mobility trigger in preference to any reference signal configuration associated with a reference signal receivable from the target network node included in a reference signal configuration associated with a reference signal receivable from one or more network nodes of the radio access network.

[0025] According to some embodiments, if the user equipment evaluates that neither the reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network nor the mobility trigger include a reference signal configuration associated with reference signals receivable from the target network node, the user equipment is configured to perform initiating a random access request to the target network node indicated by the mobility trigger.

[0026] According to some embodiments, the user equipment is configured to monitor reference signals receivable from the target network node in accordance with the evaluated associated configuration at least until updated reference signal configurations associated with the reference signals receivable from one or more network nodes of the radio access network are received from the target network node.

[0027] According to some embodiments, monitoring reference signals receivable from the target network node in accordance with the evaluated associated configuration includes monitoring at least one downlink channel received from the target network node based on reference signals receivable from the target.

[0028] According to some embodiments, the user equipment is configured to perform transmissions based on the evaluated associated target cell configuration at least until updated reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network are received from the target network node.

[0029] According to some embodiments, transmitting includes transmitting at least one uplink channel based on a reference signal receivable from the target.

[0030] According to some embodiments, a reference signal configuration associated with a reference signal receivable from a target cell of the radio access network includes at least one inter-cell beam management ICBM indicator.

[0031] According to some embodiments, a reference signal configuration associated with a reference signal receivable from one or more network nodes of a radio access network includes at least one Transmission Configuration Indicator (TCI) status indicator.

[0032] According to some embodiments, the user equipment is configured to determine a downlink reference signal or a quasi-co-located source reference signal depending on the received transmission configuration indicator status.

[0033] According to some embodiments, the user equipment is configured with at least one transmission configuration indicator state that is mapped to a downlink reference signal index associated with the target network node.

[0034] According to some embodiments, the user equipment is configured to receive a transmission configuration indicator state index that maps the reference signal to a transmission configuration indicator state, the index being determined by the network.

[0035] According to some embodiments, the mobility trigger comprises a switch command or switch parameters to be satisfied in relation to the target network node.

[0036] According to some embodiments, the mobility trigger comprises a medium access control layer control element (MAC-CE) or downlink control information (DCI) receivable by the user equipment.

[0037] According to some embodiments, the mobility trigger comprises a transmission configuration indicator TCI state that is mapped to a reference signal index associated with the target network node.

[0038] According to some embodiments, the mobility trigger comprises a downlink reference signal configuration associated with the target network node.

[0039] According to some embodiments, receiving reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network comprises receiving at least one transmission configuration indicator TCI state, wherein the at least one configuration of reference signals receivable from the target network node comprises a transmission configuration indicator TCI state associated with a physical cell identity different from a serving cell of the user equipment; and receiving a mobility trigger indicating that the user equipment switches to the target network node, wherein the mobility trigger is associated with a transmission configuration indicator TCI state associated with the target network node; The user equipment is configured to: determine a quasi-colocated source reference signal of a downlink reference signal indicated by the transmission configuration indicator TCI state or a reference signal indicated by the transmission configuration indicator TCI state without mapping the transmission configuration indicator TCI state to a target cell configuration; switch to the target network node; apply the determined downlink reference signal to monitor at least one downlink channel and, optionally, to transmit at least one uplink channel; evaluate that the user equipment does not have a transmission configuration indicator TCI state with respect to the target cell; and apply at least one rule of the quasi-colocated QCL assumption based on the applied reference signal.

[0040] According to some embodiments, if for a CORESET other than the CORESET with index 0 the user equipment is not provided with a configuration of a transmission configuration indicator state by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for the CORESET or is provided with an initial configuration of two or more transmission configuration indicator TCI states by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for the CORESET but has not received a MAC CE activation command for one of the TCI states, the user equipment shall determine whether to use the last received Channel Status Information Reference Signal (CSI-RS) with a Tracking Reference Signal (TRS-info) configured that is associated to a physical cell identity (PCI) other than the serving cell provided to the user equipment indicated by the determined transmission configuration indicator (TCI) information.the user equipment is configured to assume that the synchronization signal / physical broadcast channel SS / PBCH block identified by the user equipment and the demodulation reference signal (DM-RS) antenna port associated with physical downlink control channel (PDCCH) reception are quasi-co-located with respect to the most recent channel status information reference signal (CSI-RS) or synchronization signal block SSB index provided to the user equipment by the received configuration index provided by the mobility trigger or by the decision that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility as part of a Layer 1 / Layer 2 triggered mobility LTM trigger command or an equivalent message triggering a cell switch to a new target cell, or optionally by the received configuration index provided by the mobility trigger or by the decision that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility as part of a Layer 1 / Layer 2 triggered mobility LTM trigger command from the user equipment's serving cell indicated by the configuration index or in any message triggering a cell switch to the target cell.

[0041] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network does not include a configuration of reference signals receivable from a target network node, and the received mobility trigger indicating that the user equipment switches to the target network node includes a configuration of reference signals receivable from the target network node, causing the user equipment to switch to the target network node and to monitor reference signals receivable from the target network node in accordance with the configuration of reference signals receivable from the target network node included in the received mobility trigger.

[0042] According to some embodiments, the user equipment is connected to a serving cell, and the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network are received from the serving cell and do not include configurations of reference signals receivable from a target network node, and the received mobility trigger includes a Medium Access Control Layer Control Element MAC CE message from the serving cell indicating that the user equipment switches to the target network node and includes configurations of reference signals receivable from the target network node in form of a transmission configuration indicator TCI state or quasi-colocated QCL source information related to the target cell, and the user equipment is adapted to: determine the reference signals or source reference signals indicated by the TCI state or quasi-colocated QCL source information; switch to the target network node; monitor the reference signals receivable from the target network node by monitoring at least one downlink channel and, optionally, applying the determined reference signals for transmitting at least one uplink channel, causing the user equipment to consider the target cell as not having the indicated transmission configuration indicator TCI state.

[0043] According to some embodiments, the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network do not include configurations of reference signals receivable from a target network node, and the received mobility trigger indicating that the user equipment should switch to the target network node does not include configurations of reference signals receivable from the target network node, causing the user equipment to decide to switch to the target network node and to initiate a random access request to the target cell.

[0044] According to some embodiments, the user equipment is connected to a serving cell, the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network are received from the serving cell and do not include configurations of reference signals receivable from a target network node, the received mobility trigger comprises a medium access control layer control element MAC CE message from the serving cell indicating that the user equipment switches to the target network node and does not include configurations of reference signals receivable from the target network node, causing the user equipment to decide to switch to the target network node and to initiate a contention-based random access request to the target cell.

[0045] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a configuration of reference signals receivable from the target network node, and the received mobility trigger indicating that the user equipment switches to the target network node does not comprise a configuration of reference signals receivable from the target network node, causing the user equipment to switch to the target network node and to monitor reference signals receivable from the target network node in accordance with the configuration of reference signals receivable from the target network node included in the received reference signal configuration associated with the reference signals receivable from the one or more network nodes of the radio access network.

[0046] According to some embodiments, the user equipment is connected to a serving cell, and the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network includes a medium access control layer control element MAC CE message from the serving cell and includes a transmission configuration indicator TCI state or an inter-cell beam management ICBM indication related to a target cell (i.e., the TCI state of a cell having a different PCI than the serving cell is indicated by the UE to be applied for at least DL or UL channels (or both)), and the received mobility trigger is a medium access control layer control element MAC CE message from the serving cell indicating that the user equipment should switch to the target network node. The received mobility trigger includes a CE message and does not include a configuration of a reference signal receivable from the target network node, and the user equipment is configured to: determine a reference signal or a source reference signal indicated by the received transmission configuration indicator TCI state or inter-cell beam management ICBM indication; switch to the target network node; monitor the determined reference signal receivable from the target network node by monitoring at least one downlink channel and, optionally, applying the determined reference signal to transmit at least one uplink channel, and the user equipment is configured to consider that it does not have the indicated transmission configuration indicator TCI state with respect to the target cell.

[0047] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a configuration of reference signals receivable from a target network node, and the user equipment is caused to communicate with the target cell using the received configuration of reference signals receivable from the target network node while leaving the serving cell unchanged, and the received mobility trigger indicating that the user equipment should switch to the target network node comprises a configuration of reference signals receivable from the target network node, and causes the user equipment to switch to the target network node and to monitor reference signals receivable from the target network node in accordance with the configuration of reference signals receivable from the target network node comprised in the received mobility trigger.

[0048] According to some embodiments, a user equipment is connected to a serving cell, and a received reference signal configuration associated with a reference signal receivable from one or more network nodes of the radio access network includes a medium access control layer control element MAC CE message from the serving cell and includes a transmission configuration indicator TCI state or an inter-cell beam management ICBM indication related to a target cell, and the user equipment is adapted to perform, while maintaining the serving cell, communicating with the target cell using the received transmission configuration indicator TCI state as a pseudo-co-located assumption for monitoring the target cell, and the received mobility trigger is a medium access control layer control element MAC CE message from the serving cell indicating that the user equipment should switch to the target network node. the CE message includes a configuration of reference signals receivable from the target network node in the form of a transmission configuration indicator TCI state or quasi-colocated QCL source information related to the target cell, and the user equipment is configured to: determine a reference signal or source reference signal indicated by the transmission configuration indicator TCI state or quasi-colocated QCL source information included in the received mobility trigger to overwrite a previous transmission configuration indicator TCI state or quasi-colocated QCL assumption; switch to the target network node; monitor reference signals receivable from the target network node by applying the determined reference signal for transmitting at least one downlink channel and, optionally, at least one uplink channel, causing the user equipment to consider that it does not have the indicated transmission configuration indicator TCI state with respect to the target cell.

[0049] According to various, but not necessarily all, example embodiments, there is provided a method performed by a user equipment of a radio access network, the method including: determining that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; receiving reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network, the configurations may include configurations for reference signals receivable from a target network node; receiving a mobility trigger indicating that the user equipment should switch to the target network node, the mobility trigger may include configurations associated with reference signals receivable from the target network node; switching to the target network node; evaluating whether the mobility trigger or the received reference signal configurations include configurations associated with reference signals receivable from the target network node, and if so, monitoring reference signals receivable from the target network node in accordance with the evaluated associated configurations.

[0050] According to some embodiments, one of the one or more network nodes is a network node supporting a serving cell to which the user equipment is connected.

[0051] According to some embodiments, the target network node is a network node that supports a target cell or a target candidate cell, which may include a cell to which the user equipment switches from the serving cell.

[0052] According to some embodiments, the network node supporting the serving cell and the network node supporting the target cell or target candidate cell are the same node or different nodes, and both nodes may or may not be physically co-located.

[0053] According to some embodiments, there is provided a user equipment of a radio access network comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to operate and perform the following steps:

[0054] The user equipment may determine that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility. The determination may be based on receiving a configuration message or an indication from the network. The configuration may include a radio resource control (RRC) message. The message may be received from the user equipment's serving cell or a serving network node.

[0055] The user equipment may receive a reference signal configuration associated with a receivable reference signal from one or more network nodes of a radio access network. The reference signal configuration may be received at the user equipment. The reference signal configuration may be based on receiving a configuration message or an indication from the network. The reference signal configuration may be based on receiving a configuration message or an indication from a serving cell or a serving network node of the user equipment. The receiving may include receiving a radio resource control (RRC) message or a medium access control (MAC) control element (CE). The reference signal configuration may include any suitable indication or mapping of a reference signal configuration. The reference signal configuration may include, for example, a transmission configuration indication (TCI) state, a quasi-co-located QCL indication of the reference signal, a direct indication of the reference signal, or an inter-cell beam management ICBM reference, etc.

[0056] The received configuration may include configurations of reference signals receivable from the target network node. The received configuration may include configurations associated with a serving cell or a network node. The received configuration may include configurations associated with a cell other than the serving cell or the target cell. The configuration may explicitly include reference configurations (e.g., TCI state, QCL, reference signals) associated with the user equipment's serving cell. The configuration may or may not further include explicit reference configurations associated with the target cell and / or implicit reference configurations associated with the target cell. Such implicit references may, for example, be associated in some way with the serving cell configuration.

[0057] The user equipment may receive a mobility trigger indicating that the user equipment switches to a target network node. The mobility trigger may be received at the user equipment. The mobility trigger may be based on receiving a configuration message or an instruction from the network. The mobility trigger may be based on receiving a configuration message or an instruction from the user equipment's serving cell or serving network node. The mobility trigger may be transmitted as part of a MAC CE message transmitted to the UE from a serving network node, i.e., a serving network node supporting the serving cell to which the UE is connected, and may include or support the functionality of a distributed unit (DU).

[0058] The mobility trigger may include a configuration associated with a reference signal receivable from the target network node. As mentioned above, the received configuration may include a configuration for a reference signal receivable from the target network node. The received configuration may include a configuration associated with a serving cell or a network node. The received configuration may include a configuration associated with a cell other than the serving cell or the target cell. The configuration may explicitly include reference configurations (e.g., TCI state, QCL, reference signals) associated with the serving cell of the user equipment. The configuration may or may not further include explicit reference configurations associated with the target cell and / or implicit reference configurations associated with the target cell. Such implicit references may, for example, be associated in some way with the serving cell configuration.

[0059] The user equipment may switch to the target network node. The switching may include, for example, a handover from a serving cell to the target cell. The switching may include, for example, the UE performing a random access procedure or the like to perform the handover / switch to the target cell. The switching may occur without the user equipment performing a random access procedure to the target cell. The evaluating may be performed before such a switching step, since the switching may be performed after the evaluating step.

[0060] The user equipment may evaluate whether the mobility trigger or the received reference signal configuration includes a configuration associated with a reference signal receivable from the target network node.

[0061] In response to detecting that the mobility trigger or the received reference signal configuration includes a configuration associated or associable with a reference signal receivable from the target network node, the user equipment may be configured to monitor the reference signal receivable from the target network node in accordance with the detected associated configuration.

[0062] In response to detecting that both the mobility trigger and the received reference signal configuration include a configuration associated or associable with a reference signal receivable from the target network node, the user equipment may select the most recently received configuration, and the user equipment may then be configured to monitor reference signals receivable from the target network node in accordance with the detected associated configuration.

[0063] In response to detecting that neither the mobility trigger nor the received reference signal configuration includes a configuration associated with or associable with a reference signal receivable from the target network node, the user equipment may be configured to perform a random access procedure to the target node.

[0064] The method may further include assuming that, after switching to the target network node, reference signal configurations associated with reference signals receivable from the target network node are unknown. As an example, the UE determines that an indication of a TCI state has not been received or is not indicated (i.e., a TCI state to apply to communications, such as DL / UL or both, is not indicated). An example of reference signals receivable from the target network node being unknown may refer to a case where the UE is not indicated a TCI state and applies pre-determined QCL information to transmission and / or reception of channels / signals.

[0065] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a transmission configuration indicator state, the configuration comprising a transmission configuration indicator state of reference signals receivable from a target network node, and after switching to the target network node, the user equipment is configured to not apply the transmission configuration indicator states of reference signals receivable from the target network node that were received before switching to the target network node.

[0066] According to some embodiments, if the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network include a configuration for reference signals receivable from the target network node, the user equipment is configured to perform monitoring of reference signals receivable from the target network node in accordance with the evaluated associated configurations at least until a mobility trigger is received.

[0067] According to some embodiments, evaluating whether a reference signal or a reference signal configuration associated with a mobility trigger includes a configuration for a reference signal receivable from the target network node comprises selecting a reference signal configuration associated with a reference signal receivable from the target network node received in the mobility trigger in preference to any reference signal configuration associated with a reference signal receivable from the target network node included in a reference signal configuration associated with a reference signal receivable from one or more network nodes of the radio access network.

[0068] According to some embodiments, if the user equipment evaluates that neither the reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network nor the mobility trigger include a reference signal configuration associated with reference signals receivable from the target network node, the user equipment is configured to perform initiating a random access request to the target network node indicated by the mobility trigger.

[0069] According to some embodiments, the method includes monitoring reference signals receivable from the target network node in accordance with the evaluated associated configuration at least until updated reference signal configurations associated with the reference signals receivable from one or more network nodes of the radio access network are received from the target network node.

[0070] According to some embodiments, monitoring reference signals receivable from the target network node in accordance with the evaluated associated configuration includes monitoring at least one downlink channel received from the target network node based on reference signals receivable from the target.

[0071] According to some embodiments, the method includes performing transmissions based on the evaluated associated target cell configuration at least until updated reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network are received from the target network node.

[0072] According to some embodiments, transmitting includes transmitting at least one uplink channel based on a reference signal receivable from the target.

[0073] According to some embodiments, a reference signal configuration associated with a reference signal receivable from a target cell of the radio access network includes at least one inter-cell beam management ICBM indicator.

[0074] According to some embodiments, a reference signal configuration associated with a reference signal receivable from one or more network nodes of the radio access network comprises at least one transmission configuration indicator TCI status indicator.

[0075] According to some embodiments, the method includes determining a downlink reference signal or a quasi-co-located source reference signal as a function of the received transmission configuration indicator status.

[0076] According to some embodiments, the user equipment is configured with at least one transmission configuration indicator state that is mapped to a downlink reference signal index associated with the target network node.

[0077] According to some embodiments, the method includes receiving a transmission configuration indicator state index that maps the reference signal to a transmission configuration indicator state, the index being determined by the network.

[0078] According to some embodiments, the mobility trigger comprises a switch command or switch parameters to be satisfied in relation to the target network node.

[0079] According to some embodiments, the mobility trigger comprises a medium access control layer control element MAC-CE or downlink control information DCI receivable by the user equipment.

[0080] According to some embodiments, the mobility trigger comprises a transmission configuration indicator TCI state that is mapped to a reference signal index associated with the target network node.

[0081] According to some embodiments, the mobility trigger comprises a downlink reference signal configuration associated with the target network node.

[0082] According to some embodiments, receiving reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network comprises receiving at least one transmission configuration indicator TCI state, wherein the at least one configuration of reference signals receivable from the target network node comprises a transmission configuration indicator TCI state associated with a physical cell identity different from a serving cell of the user equipment; and receiving a mobility trigger indicating that the user equipment switches to the target network node, wherein the mobility trigger is associated with a transmission configuration indicator TCI state associated with the target network node; The user equipment is configured to: determine a quasi-colocated source reference signal of a downlink reference signal indicated by the transmission configuration indicator TCI state or a reference signal indicated by the transmission configuration indicator TCI state without mapping the transmission configuration indicator TCI state to a target cell configuration; switch to the target network node; apply the determined downlink reference signal to monitor at least one downlink channel and, optionally, to transmit at least one uplink channel; evaluate that the user equipment does not have a transmission configuration indicator TCI state with respect to the target cell; and apply at least one rule of the quasi-colocated QCL assumption based on the applied reference signal.

[0083] According to some embodiments, for a CORESET other than the CORESET with index 0, the user equipment is provided with no configuration of a transmission configuration indicator state by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for the CORESET, or is provided with an initial configuration of two or more transmission configuration indicator TCI states by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for the CORESET, but has not configured a MAC address for one of the TCI states.If the UE has not received a CE activation command, the UE shall also determine whether the UE has received a CE activation command for the most recently received CSI-RS or SSB for which a tracking reference signal TRS-info is configured, associated with a physical cell identity PCI other than the serving cell provided to the UE as indicated by the determined transmission configuration indicator TCI information, or optionally, a most recently received CSI-RS provided to the UE by a received configuration index provided by a mobility trigger, or by a decision that the UE is configured to apply Layer 1 or Layer 2 triggered mobility as part of a Layer 1 / Layer 2 triggered mobility LTM trigger command or an equivalent message triggering a cell switch to a new target cell. or synchronization signal block SSB index, or optionally, by a mobility trigger or a decision that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility as part of a Layer 1 / Layer 2 triggered mobility LTM trigger command from the user equipment's serving cell indicated by the configuration index, or in any message triggering a cell switch to the target cell, the user equipment is configured to assume that the synchronization signal / physical broadcast channel SS / PBCH block identified by the user equipment and the demodulation reference signal DM-RS antenna port associated with physical downlink control channel PDCCH reception are quasi-co-located.

[0084] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network does not include a configuration of reference signals receivable from a target network node, and the received mobility trigger indicating that the user equipment switches to the target network node includes a configuration of reference signals receivable from the target network node, causing the user equipment to switch to the target network node and to monitor reference signals receivable from the target network node in accordance with the configuration of reference signals receivable from the target network node included in the received mobility trigger.

[0085] According to some embodiments, the user equipment is connected to a serving cell, and the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network are received from the serving cell and do not include configurations of reference signals receivable from a target network node, and the received mobility trigger includes a Medium Access Control Layer Control Element MAC CE message from the serving cell indicating that the user equipment switches to the target network node and includes configurations of reference signals receivable from the target network node in form of a transmission configuration indicator TCI state or quasi-colocated QCL source information related to the target cell, and the user equipment is adapted to: determine the reference signals or source reference signals indicated by the TCI state or quasi-colocated QCL source information; switch to the target network node; monitor the reference signals receivable from the target network node by monitoring at least one downlink channel and, optionally, applying the determined reference signals for transmitting at least one uplink channel, causing the user equipment to consider the target cell as not having the indicated transmission configuration indicator TCI state.

[0086] According to some embodiments, the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network do not include configurations of reference signals receivable from a target network node, and the received mobility trigger indicating that the user equipment should switch to the target network node does not include configurations of reference signals receivable from the target network node, causing the user equipment to decide to switch to the target network node and to initiate a random access request to the target cell.

[0087] According to some embodiments, the user equipment is connected to a serving cell, the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network are received from the serving cell and do not include configurations of reference signals receivable from a target network node, the received mobility trigger comprises a medium access control layer control element MAC CE message from the serving cell indicating that the user equipment switches to the target network node and does not include configurations of reference signals receivable from the target network node, causing the user equipment to decide to switch to the target network node and to initiate a contention-based random access request to the target cell.

[0088] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a configuration of reference signals receivable from the target network node, and the received mobility trigger indicating that the user equipment switches to the target network node does not comprise a configuration of reference signals receivable from the target network node, causing the user equipment to switch to the target network node and to monitor reference signals receivable from the target network node in accordance with the configuration of reference signals receivable from the target network node included in the received reference signal configuration associated with the reference signals receivable from the one or more network nodes of the radio access network.

[0089] According to some embodiments, a user equipment is connected to a serving cell, and received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network include a medium access control layer control element MAC CE message from the serving cell and include a transmission configuration indicator TCI state or an inter-cell beam management ICBM indication related to a target cell, and a received mobility trigger includes a medium access control layer control element MAC CE message from the serving cell indicating that the user equipment switches to the target network node, and the received mobility trigger does not include a configuration of reference signals receivable from the target network node, and the user equipment is configured to: determine a reference signal or a source reference signal indicated by the received transmission configuration indicator TCI state or the inter-cell beam management ICBM indication; switch to the target network node; and monitor the determined reference signal receivable from the target network node by monitoring at least one downlink channel and, optionally, applying the determined reference signal to transmit at least one uplink channel, causing the user equipment to consider that it does not have the indicated transmission configuration indicator TCI state with respect to the target cell.

[0090] According to some embodiments, the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a configuration of reference signals receivable from a target network node, and the user equipment is caused to communicate with the target cell using the received configuration of reference signals receivable from the target network node while leaving the serving cell unchanged, and the received mobility trigger indicating that the user equipment should switch to the target network node comprises a configuration of reference signals receivable from the target network node, and causes the user equipment to switch to the target network node and to monitor reference signals receivable from the target network node in accordance with the configuration of reference signals receivable from the target network node comprised in the received mobility trigger.

[0091] According to some embodiments, a user equipment is connected to a serving cell, and a received reference signal configuration associated with a reference signal receivable from one or more network nodes of the radio access network includes a medium access control layer control element MAC CE message from the serving cell and includes a transmission configuration indicator TCI state or an inter-cell beam management ICBM indication related to a target cell, and the user equipment is adapted to perform, while maintaining the serving cell, communicating with the target cell using the received transmission configuration indicator TCI state as a pseudo-co-located assumption for monitoring the target cell, and the received mobility trigger is a medium access control layer control element MAC CE message from the serving cell indicating that the user equipment should switch to the target network node. the CE message includes a configuration of reference signals receivable from the target network node in the form of a transmission configuration indicator TCI state or quasi-colocated QCL source information related to the target cell, and the user equipment is configured to: determine a reference signal or source reference signal indicated by the transmission configuration indicator TCI state or quasi-colocated QCL source information included in the received mobility trigger to overwrite a previous transmission configuration indicator TCI state or quasi-colocated QCL assumption; switch to the target network node; monitor reference signals receivable from the target network node by applying the determined reference signal for transmitting at least one downlink channel and, optionally, at least one uplink channel, causing the user equipment to consider that it does not have the indicated transmission configuration indicator TCI state with respect to the target cell.

[0092] According to various, but not necessarily all, exemplary embodiments, there is provided a computer program product operable, when executed on a computer, to perform a method, the method including: determining that a user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; receiving reference signal configurations associated with reference signals receivable from one or more network nodes of a radio access network, the configurations may include configurations for reference signals receivable from a target network node; receiving a mobility trigger indicating that the user equipment should switch to the target network node, the mobility trigger may include configurations associated with reference signals receivable from the target network node; switching to the target network node; evaluating whether the mobility trigger or the received reference signal configurations include configurations associated with reference signals receivable from the target network node, and if so, monitoring reference signals receivable from the target network node in accordance with the evaluated associated configurations.

[0093] According to various, but not necessarily all, example embodiments, there is provided a network node of a radio access network comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause a user equipment to at least: determine that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; provide to the user equipment reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network, where the configurations may include configurations for reference signals receivable from a target network node; and provide to the user equipment a mobility trigger indicating that the user equipment switches to the target network node, where the mobility trigger may include configurations associated with reference signals receivable from the target network node.

[0094] According to various, but not necessarily all, example embodiments, there is provided a method performed by a network node of a radio access network, the method including: determining that a user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; providing to the user equipment a reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network, the configuration may include a configuration for reference signals receivable from a target network node; and providing to the user equipment a mobility trigger indicating that the user equipment switches to the target network node, the mobility trigger may include a configuration associated with reference signals receivable from the target network node.

[0095] According to various, but not necessarily all, exemplary embodiments, there is provided a computer program product operable to perform a method, when executed on a computer, comprising: determining that a user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; providing to the user equipment a reference signal configuration associated with reference signals receivable from one or more network nodes of a radio access network, the configuration may include a configuration for reference signals receivable from a target network node; and providing to the user equipment a mobility trigger indicating that the user equipment switches to the target network node, the mobility trigger may include a configuration associated with reference signals receivable from the target network node.

[0096] Aspects and embodiments relate to mechanisms and procedures used to support Layer 1 / Layer 2 (L1 / L2) triggered inter-cell mobility (LTM). Aspects and embodiments may provide mechanisms and procedures related to L1 / L2-based inter-cell mobility that support reduced mobility latency. Some described aspects and embodiments provide medium access control (MAC) control signaling, such as a MAC control element (CE), that may indicate a transmission configuration indicator (TCI) state (or other beam information) to activate in a UE in association with a mobility target cell.

[0097] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and in combinations other than those explicitly set out in the claims.

[0098] It will be understood that where features of an apparatus are described as operable to provide a function, this includes features of an apparatus that provide that function or that are adapted or configured to provide that function.

[0099] Several exemplary embodiments will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0100] [Figure 1] FIG. 1 is a diagram illustrating schematically some major components of a 5G new radio (NR) wireless communications network. [Figure 2A] FIG. 10 illustrates the format of a transmission configuration indicator (TCI) status information element. [Figure 2B] FIG. 10 illustrates the format of a transmission configuration indicator (TCI) status information element. [Figure 3] FIG. 1 is a signaling diagram showing signaling supporting one possible implementation. [Figure 4] FIG. 1 is a signaling diagram illustrating signaling supporting one possible implementation. [Figure 5] FIG. 1 is a signaling diagram illustrating signaling supporting one possible implementation. [Figure 6] FIG. 1 is a signaling diagram illustrating signaling supporting one possible implementation. [Figure 7] 1 is a flow chart outlining steps according to one arrangement. DETAILED DESCRIPTION OF THE INVENTION

[0101] Before describing the exemplary embodiments in further detail, we first describe the general framework of a wireless communications network and provide an overview of the architecture in that context.

[0102] The presented concepts may be implemented across a wide range of telecommunications systems, network architectures, and communication standards. Various aspects will be outlined with reference to wireless communication systems. Such wireless communication systems typically include three interacting domains: a core network, a radio access network (RAN), and a user equipment (UE).

[0103] The RAN may be configured to implement any suitable wireless communication technology (or combination of technologies) to provide radio access to UEs. According to one example, the RAN may be configured to operate in accordance with the 3rd Generation Partnership Project (3GPP) New Radio (NR) standard, typically referred to as 5G.

[0104] As a user equipment (UE) moves within a wireless communication system, it may move within areas of radio coverage (cells) supported by one or more radio access network nodes. Maintaining the ability of a UE to communicate effectively with the wireless communication system as it moves within areas of radio coverage is typically referred to as mobility. The operating characteristics of cells supported by network access nodes within a wireless communication network may vary. A wireless communication system may include various transmission / reception points (TRPs).

[0105] FIG. 1A schematically illustrates some key components of a 5G New Radio (NR) network topology. A 5G NR network is envisioned to utilize multiple transmission / reception points (mTRPs) to improve reliability, coverage, and capacity performance through flexible deployment scenarios. Multi-TRPs operate to mitigate inter-cell interference through dynamic coordination between multiple TRPs, providing joint scheduling and transmission / reception. Typically, wireless devices, such as cell-edge UEs, may be served by multiple TRPs to improve signal transmission and / or reception, resulting in increased throughput. The following description may provide further details of alternatives, modifications, and variations in a 5G NR network, including a gNB, which provides NR user plane and control plane protocol termination to UEs and is connected to a 5G NR network via an NG interface, for example, in accordance with 3GPP TS 38.300 V16.6.0(2021-06) Section 3.2, which is incorporated by reference.

[0106] The gNB Central Unit (gNB-CU) contains a logical node that controls the operation of one or more gNB-DUs, for example, hosting the RRC (Radio Resource Control), SDAP (Service Data Adaptation Protocol), and PDCP (Packet Data Convergence Protocol) protocols of a gNB, or the RRC and PDCP protocols of an en-gNB. The gNB-CU terminates the F1 interface connected to the gNB-DU.

[0107] The gNB distributed unit (gNB-DU) includes a logical node that hosts, for example, the RLC (radio link control), MAC (medium access control), and PHY (physical) layers of a gNB or en-gNB, and its operation is partially controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0108] The gNB-CU control plane (gNB-CU-CP) includes logical nodes that host, for example, the control plane portions of the RRC and PDCP protocols of the en-gNB or gNB-CU of a gNB. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU.

[0109] The gNB-CU-User Plane (gNB-CU-UP) includes logical nodes that host, for example, the user plane portion of the PDCP protocol of the gNB-CU of the en-gNB, as well as the user plane portion of the PDCP protocol and the SDAP protocol of the gNB-CU of the gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, in accordance with 3GPP TS 38.401 V16.6.0(2021-07) Section 3.1, which is incorporated by reference.

[0110] Between the central unit and the distributed units, various functional divisions, called options, are possible. Option 1 (split like 1A): - This option's functional division is similar to the DC 1A architecture: RRC is in the central unit; PDCP, RLC, MAC, physical layer, and RF are in distributed units. Option 2 (3C-like split): - This optional functional division is similar to the 3C architecture of DC: RRC and PDCP are in the central unit, while RLC, MAC, physical layer, and RF are in the distributed units. Option 3 (Intra-RLC Splitting): - Low RLC (sub-functions of RLC), MAC, physical layer, and RF are in the distributed units. PDCP and high RLC (other sub-functions of RLC) are in the central unit. Option 4 (RLC-MAC Split): - MAC, physical layer, and RF are in the distributed units. PDCP and RLC are in the central unit. Or, for example, according to 3GPP TR 38.801 V14.0.0(2017-03) Section 11, which is incorporated by reference. The gNB supports various protocol layers, including Layer 1 (L1) - the physical layer.

[0111] Layer 2 (L2) of NR is divided into sublayers such as Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP).

[0112] The physical layer provides transport channels to the MAC sublayer. - The MAC sublayer provides logical channels to the RLC sublayer. - The RLC sublayer provides the RLC channel to the PDCP sublayer. - The PDCP sublayer provides the radio bearer to the SDAP sublayer. - The SDAP sublayer provides QoS flows to the 5GC. - Comp. refers to header compression and Segm. refers to segmentation. - Control channels include (BCCH, PCCH).

[0113] Layer 3 (L3) includes radio resource control (RRC), for example, according to 3GPP TS 38.300 V16.6.0 (2021-06) Section 6, which is incorporated by reference.

[0114] A RAN (Radio Access Network) node or network node or central or distributed node, e.g., a gNB, a base station, a gNB CU, or a gNB DU, or a portion thereof, may be implemented using an apparatus having at least one processor and / or at least one memory (containing computer-readable instructions (computer programs)) configured to support and / or provide and / or process CU- and / or DU-related functions and / or features, and / or at least one protocol (sub-)layer of the RAN (Radio Access Network), e.g., Layer 2 and / or Layer 3. They may also be implemented using specific means configured to perform respective specific tasks, e.g., Layer 3 means for performing Layer 3 operations, Layer 2 means for performing Layer 2 operations, etc. A central node may, for example, perform CU-CP functions and / or CP-UP functions.

[0115] The gNB CU portion and the gNB DU portion may be, for example, co-located or physically separated. The gNB DU may be further divided, for example, into two portions, for example, a portion including processing equipment and a portion including antennas. The central unit (CU) may also be referred to as a BBU / REC / RCC / C-RAN / V-RAN, O-RAN, or a portion thereof. The distributed unit (DU) may also be referred to as an RRH / RRU / RE / RU, or a portion thereof.

[0116] The gNB-DU can support one or more cells and function as a serving cell to a user equipment (UE).

[0117] In other words, a 5G base station or "network node", referred to as a gNB, can be divided into two physical entities, referred to as a CU (Central Unit) and a DU (Distributed Unit).

[0118] The CU provides support for the upper layers of the protocol stack, such as SDAP, PDCP, and RRC (and especially Layer 3 protocols like RRC), while the DU provides support for the lower layers of the protocol stack, such as RLC, MAC, and the physical layer (especially Layer 1 like the physical layer, and Layer 2 protocols like RLC and MAC). It should also be noted that the SDAP layer does not exist when the CU is connected to a 4G core network, because a 5G core network must be present to support SDAP. In practical terms, there is a single CU per gNB, but one CU controls multiple DUs; for example, more than 100 DUs can be connected to one CU.

[0119] Each DU can support one or multiple cells, so one gNB can control hundreds of cells, unlike a 4G base station. Also, note that the interface between the CU and the DU is called F1, and according to 3GPP, this should be an open interface, so that one CU of vendor X is connected to another DU of vendor Y.

[0120] User equipment (UE) may include wireless or mobile devices, devices having a radio interface for interacting with a RAN (Radio Access Network), smartphones, automotive devices, IoT devices, M2M devices, etc. Such UEs or devices may include at least one processor and at least one memory containing computer program code configured by the at least one processor to cause the device to perform certain operations, such as, for example, an RRC connection to the RAN. The UE is configured, for example, to generate messages (e.g., including a cell ID) to be transmitted over the air toward the RAN (e.g., to reach and communicate with a serving cell). The UE may generate and send and receive RRC messages including one or more RRC PDUs (Packet Data Units).

[0121] The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0(2021-06) sections 42.1 and 4.4, which are incorporated by reference).

[0122] For example, when an RRC connection is established, the UE is in either an RRC_CONNECTED state or an RRC_INACTIVE state.

[0123] In the RRC_CONNECTED state, the UE may: Remember AS context - Transfer unicast data to and from the UE - monitoring a control channel associated with the shared data channel to determine whether data is scheduled on the data channel; - Provides channel quality and feedback information - Perform neighbor cell measurements and measurement reporting

[0124] The RRC protocol includes the following main functions, for example: - RRC connection control - Measurement setup and reporting - Establishing / modifying / releasing measurement configurations (e.g., intra-frequency, inter-frequency, and inter-RAT measurements) - Setup and release of measurement gaps - Measurement report

[0125] As networks evolve, particularly in 5G New Radio (NR) systems, inter-cell mobility is configured to be Layer 1 (L1 or PHY layer) or Layer 2 (L2 or MAC layer) centric (L1 / L2 centric), rather than being controlled by the core network. Within the 5G NR framework, various methodologies for implementing L1 / L2 centric inter-cell mobility are possible and may be selected based on various operational scenarios, as further described below.

[0126] Various configurations are described for supporting L1 / L2-centric inter-cell mobility methodologies and signaling, which recognize various complexities associated with supporting mobility for UEs operating in a RAN where the serving or source cell may have a configuration that may differ significantly from the configuration associated with one or more candidate serving cells.

[0127] To reduce mobility latency, the 3GPP Rel-18 Working Item Description (WID) on Further NR Mobility Enhancements, RP-222332, agreed one of its goals on standardizing mechanisms and procedures for Layer 1 / Layer 2 (L1 / L2) triggered inter-cell mobility (LTM), including the following items:

[0128] 1. To specify mechanisms and procedures for L1 / L2 based inter-cell mobility for reducing mobility latency: ○ Configuration and maintenance of multiple candidate cells to enable rapid application of candidate cell configurations [RAN2, RAN3] Dynamic switching mechanism between candidate serving cells (including SpCell and SCell) for possible applicable scenarios based on L1 / L2 signaling [RAN2, RAN1] L1 extensions for inter-cell beam management including L1 measurements and reporting and beam direction [RAN1, RAN2] Note 1: Early RAN2 involvement is needed, including the possibility of further clarifying the interaction of this bullet with the previous one. ○ Timing advance management [RAN1, RAN2] ○ CU-DU interface signaling to support L1 / L2 mobility as needed [RAN3] Note 2: FR2 specific extensions, if any, are not excluded. NOTE 3: The L1 / L2 based inter-cell mobility procedure is applicable to the following scenarios: Standalone, CA, and NR-DC cases where the serving cell changes within one CG Intra-DU case and intra-CU and inter-DU case (applicable to standalone and CA: no new RAN interfaces are envisaged) Both intra- and inter-frequency · Both FR1 and FR2 The source and target cells may or may not be synchronized.

[0129] RAN2 agreed to the following at RAN2#119bis:

[0130] The following relevant agreements were reached in RAN2#119b:

[0131] RAN2 assumes that it is up to RAN1 whether to use the unified TCI framework as a baseline for beam direction for L1 / L2 mobility (RAN2 recognizes that L1 / L2 mobility needs to support the inter-frequency case).

[0132] Before the L1 / L2 dynamic switching is triggered, an L1 / L2 inter-cell mobility candidate (target) configuration is received in an RRC message.

[0133] RAN2 assumes that L1 / 2 mobility trigger information is conveyed in MAC CE. It remains to be seen whether MAC CE messages or Downlink Control Information (DCI) messages will be used to actually trigger the mobility event.

[0134] RAN2 assumes that the MAC CE for L1 / 2 mobility triggers contains at least a candidate configuration index. It remains to be seen whether the MAC CE may indicate the TCI status (or other beam information) to the UE to enable target cell activation.

[0135] RAN1 (in RAN1#110-bis) agreed to further consider the following: - RAN1 will further consider whether the beam direction of candidate cells' L1 / L2 mobility needs to be designed to the following specific TCI frameworks and their potential impact on the RAN1 standard. Option A: Beam direction for Rel-18 L1 / L2 mobility will be designed based on the Rel-17 TCI framework mechanism. Option B: Beam direction for Rel-18 L1 / L2 mobility will be designed based on the Rel-15 TCI framework mechanism. Option C: Beam direction for Rel-18 L1 / L2 mobility will be designed based on the TCI framework mechanisms of both Rel-15 and Rel-17.

[0136] Transmission Configuration Indicator (TCI) Status Information about reference signals receivable by the UE from the network access node may be provided to the UE in TCI state signaling. A transmission configuration indicator (TCI) may be dynamically transmitted to the UE in downlink control signaling (e.g., DCI messaging), and the TCI state may include information about configurations such as, for example, QCL relationships between downlink (DL) reference signals (RSs) and physical downlink shared channel (PDSCH) demodulation reference signal (DMRS) ports within one channel status information reference signal (CSI-RS) set.

[0137] 3GPP TS 38.331 presents a general format for TCI-state information provided within a network, the details of which are shown in Figures 2A and 2B.

[0138] Typically, a list of up to "M" TCI-State configurations can be configured for the UE in the higher layer (RRC ReConfig) parameter PDSCH-Config to decode the PDSCH according to the detected PDCCH containing DCI for the UE and a given serving cell, where M depends on the UE capabilities.

[0139] Each TCI-State includes parameters related to a quasi-co-location relationship between one or two downlink reference signals. Furthermore, each TCI-State includes parameters for configuring a quasi-co-location relationship between one or two downlink reference signals and a DM-RS port of a PDSCH, a DM-RS port of a PDCCH, or a CSI-RS port of a CSI-RS resource. As a result, the TCI information already provided to the UE typically includes quasi-co-location (QCL) information. Two signals transmitted from the same antenna port typically experience the same wireless channel. Two signals transmitted from two different antenna ports typically experience different wireless conditions. It is recognized that there may be cases where signals transmitted from two different antenna ports experience wireless channels with common characteristics. In such cases, these antenna ports are said to be quasi-co-located (QCL).

[0140] QCL type definitions are provided in TS 38.214, with four types indicating which large-scale channel characteristics are common between sets of antenna ports. - "typeA": {Doppler shift, Doppler spread, average delay, delay spread} - "type B": {Doppler shift, Doppler spread} - "typeC": {Doppler shift, average delay} - "typeD":{spatial Rx parameters}

[0141] QCL information provided in the TCI may include: 1) Reference signal (RS) 2) QCL type = type A, type B, type C, and type D 3) Bandwidth portion (bwp) where RS is located

[0142] The TCI and QCL information may be utilized in implementing mechanisms and signaling to support mobility within the network.

[0143] For example, when switching serving beams, it is proposed that one of the following options is allowed for QCL-info: (1) qcl-Type1: referenceSignal = Tracking RS (TRS) index, where TRS is a special setting of the CSI-RS index (see below), qcl-Type = A, qcl-Type2 (applicable only in FR2): referenceSignal = the same TRS index, qcl-Type = D. (2) qcl-Type1: referenceSignal = Tracking RS (TRS) index, qcl-Type = A, qcl-Type2 (applicable only in FR2): referenceSignal = CSI-RS index with repetition, qcl-Type = D.

[0144] Unified TCI State Framework and R18 Extensions The R17 unified TCI state framework is used as a baseline for the R18 S-DCI and m-DCI multiple TRP transmission extensions for UL multi-panel transmission. In the unified TCI state (Rel17) framework, a single TCI state can be indicated to the UE, and this TCI state, or rather the RS indicated by the TCI state, is used to assume transmission and reception of PDCCH / PDSCH / CSI-RS and / or PUCCH / PUSCH / SRS.

[0145] In the unified TCI state framework, beam indication, or rather TCI state indication (i.e., indication of which TCI state to use to assume transmission and / or reception of signals and channels associated with the TCI state), involves the following steps:

[0146] 1. For the serving cell, the unified TCI state type is configured to either joint UL / DL or separate UL / DL. In joint UL / DL, the indicated TCI state is used for uplink and downlink, while in separate, DL and UL are indicated separately (one TCI codepoint indicated in DCI can contain only DL TCI, only UL TCI, or TCI states for DL ​​and UL). If the TCI state type is joint, a single list of TCI states is configured in the UE using RRC(dl-OrJoint-TCIStateList). 2. If the TCI state type is separate, the DL TCI state list and the UL TCI state list (dl-OrJoint-TCIStateList, ul-TCI-StateList) are configured in the UE. The configuration is done using RRC signaling, and the MAC CE selects and activates up to eight (for Rel-17) TCI codepoints, one of which can be indicated in the DCI. As mentioned above, one TCI codepoint can contain only DL TCI states, only UL TCI states, or both DL and UL TCI states. 3. To indicate the TCI state (joint) or separate TCI state (UL and DL), the network provides a TCI codepoint (value in the DCI message) that corresponds to the TCI codepoint in the MAC CE that activated the TCI codepoint. Upon receiving a DCI-based beam indication (DCI codepoint), the UE applies the indicated TCI state to the indicated channel (PDSCH, PCCH / PUSCH / PUCC).

[0147] After the UE receives an initial higher layer configuration of dl-OrJoint-TCIStateList containing two or more TCIStates, and before applying the indicated TCI state from the configured TCI states: - The UE shall assume that the DM-RS of the PDSCH and the DM-RS of the PDCCH and the CSI-RS that apply the indicated TCI state are quasi-co-located with the SS / PBCH block that the UE identified during the initial access procedure. After the UE receives a higher layer configuration in dl-OrJoint-TCIStateList containing two or more TCIStates as part of a reconfiguration by synchronization procedure described in [12, TS 38.331], and before applying the TCI state indicated by the configured TCI state: - The UE shall assume that the PDSCH DM-RS and PDCCH DM-RS and CSI-RS for which the indicated TCI state applies are quasi-colocated with the SS / PBCH block or CSI-RS resource identified by the UE during the random access procedure initiated by reconfiguration via the synchronization procedure described in [12, TS 38.331].

[0148] Beam Level Mobility 3GPP TS 38.300 v17.2.0(2022-09) specifies the following: 9.2.3 Mobility in RRC_CONNECTED overview Network-controlled mobility applies to RRC_CONNECTED UEs and is classified into two types of mobility: cell-level mobility and beam-level mobility. Beam-level mobility includes intra-cell beam-level mobility and inter-cell beam-level mobility.

[0149] Beam-level mobility does not require explicit RRC signaling. Beam-level mobility can occur within a cell or between cells, the latter being called inter-cell beam management (ICBM). With ICBM, a UE can receive or transmit channels / signals dedicated to the UE via a TRP associated with a PCI different from that of the serving cell, but channels / signals not dedicated to the UE can only be received via a TRP associated with the PCI of the serving cell. The gNB provides the UE with measurement configuration via RRC signaling, including SSB / CSI resource and resource set configurations, as well as reporting and trigger conditions for triggering channel and interference measurements and reporting. For ICBM, the measurement configuration includes SSB resources associated with a PCI different from that of the serving cell. Beam-level mobility is handled by physical and MAC layer control signaling at lower layers, and RRC does not need to know which beam is being used at a given time.

[0150] SSB-based beam-level mobility is based on the SSB associated with the initial DL BWP and can only be configured for the initial DL BWP and DL BWPs that include the SSB associated with the initial DL BWP. For other DL BWPs, beam-level mobility can only be performed based on CSI-RS.

[0151] Mobility Events As can be understood in relation to the information provided above, effectively implementing L1 / L2 triggered mobility within a network may require addressing the information provided to the UE related to the candidate cell's beam. Specifically, it may be necessary to clarify the candidate cell's beam indication in Rel-18 L1 / L2 triggered mobility (LTM). For example, there may be various TCI state frameworks that need to be accommodated. For example, it may be common for a UE to operate in a network where different cells are configured with different TCI frameworks (e.g., Rel-15 or Rel-17 TCI frameworks), and such situations may arise, particularly in inter-gNB mobility scenarios. A single TCI framework may not be usable for beam indication if the target cell attempts to interpret the indicated TCI state based on its own incompatible configured TCI state pool / list.

[0152] Nevertheless, it is recognized that the configuration may be able to leverage the information provided by the TCI status indicator in the beam management framework for Rel-18 LTM-based cell switching using MAC CE and / or DCI-based mobility trigger indication. The described configuration includes a description of UE behavior upon receiving specific information as part of (or associated with) an underlying mobility trigger that configures the UE to switch to communication with a new cell.

[0153] The configuration recognizes that mechanisms that may be employed for serving cell beam management may not be well suited when lower layer triggered mobility is operational. In particular, the serving cell beam management mechanism may not capture the TCI status indication of lower layer triggered mobility when the serving cell is changed.

[0154] The configurations described in more detail below may provide specific embodiments and mechanisms for a UE to receive a TCI status indication related to a new target cell. Such indication is provided to the UE by the serving cell. The described configurations and embodiments present ways in which a UE may be configured to effectively apply such provided TCI status information, for example, when the UE receives the TCI status before a mobility trigger or as part of a mobility trigger message.

[0155] The configuration recognizes that serving cell communication can be used to provide the UE with information about the target cell, such as via TCI state. Upon receiving a mobility trigger related to that target cell, the UE may be configured to consider the (instructed / applied) TCI state of the target cell as essentially unknown (i.e., not instructed) or not explicitly configured (i.e., not instructed), but still leverage information provided by the serving cell related to the target cell. Such an approach is advantageous in terms of supporting mobility scenarios because the beam management framework for the target cell does not need to be the same as that of the source cell (i.e., the beam instruction framework can be R17 in the source cell and R15 in the target cell, and mobility still works). Furthermore, because the TCI state applied to the target cell does not need to be explicitly instructed to the UE (within the target cell configuration) prior to the mobility trigger, latency associated with mobility events can be reduced.

[0156] Before describing exemplary embodiments in further detail, an overview will first be provided.

[0157] Configurations and embodiments may provide a user equipment for use in a wireless communications network. The user equipment may receive an indication that the user equipment is configured to support Layer 1 or Layer 2 triggered mobility. In other words, the UE may support an LTM mobility procedure. According to a configuration, the user equipment may be configured to receive an indication of receivable reference signal configurations from one or more network nodes of a radio access network. According to some configurations, the user equipment may be configured to receive receivable reference signal configurations from one or more network nodes of the radio access network. The indication may include an indication of receivable reference signal configurations from a target network node (the indication may include, for example, mapping to downlink (DL) reference signals (RS), such as synchronization signal blocks (SSBs)). The indication may include an indication of configured reference signals receivable from the target network node (e.g., the indication may include TCIs). As an example, the indication may include an instruction to the user equipment to apply the indicated reference signals (TCI states) to monitoring / reception and / or transmission of at least one of a downlink channel and / or an uplink channel. Typically, a user equipment receives an indication of one or more reference signals receivable from a serving network node, but similar information regarding monitorable reference signals that may be transmitted by one or more other network nodes may be less clear to the user equipment. The user equipment may receive a mobility trigger indicating that the user equipment should switch to a target network node. In other words, the user equipment may determine or be instructed to be handed over to a cell supported by the target network node. The mobility trigger may include an indication of reference signals receivable from the target network node. The user equipment may be configured to switch to the target network node. The user equipment may be configured to evaluate whether the reference signals or the indication of the mobility trigger include an indication of reference signals receivable from the target network node, and if so, the user equipment may be configured to monitor reference signals receivable from the target network node.

[0158] In one example, the mobility trigger may include an indication (e.g., a bit field) indicating whether the mobility trigger (which may include, for example, a Medium Access Control (MAC) control element (CE) or a Downlink Control Indicator (DCI)) includes an indication of reference signals receivable from the target network node.

[0159] The indication of reference signals receivable from the target network node may include, for example, an appropriate mapping, such as from TCI states or (QCL sources) to downlink reference signals (DL RSs). Downlink reference signals may include, for example, synchronization signal blocks (SSBs) or channel status information reference signals (CSI-RSs).

[0160] In some examples, the mobility trigger may include an indication of whether a field indicating a QCL source RS ID is present in the mobility trigger. The QCL source RS ID may include, for example, a synchronization signal block (SSB), a channel status information reference signal (CSI-R), or a channel status information reference signal (CSI-RS) with a tracking reference signal (TRS) information identifier.

[0161] In some examples, the mobility trigger may include an indication of whether a field including a TCI state ID is present. The TCI state ID may indicate, for example, a synchronization signal block (SSB), a channel status information reference signal (CSI-R), or a channel status information reference signal (CSI-RS) with a tracking reference signal (TRS) information identifier.

[0162] In some examples, the mobility trigger may include an indication of the absence of a field containing a QCL source RS ID, etc. In some examples, the mobility trigger may include an indication of the absence of a field containing a TCI state ID, etc. In some examples, the mobility trigger may include an indication of the presence (or absence) of a field containing a QCL source RS ID or a TCI state ID.

[0163] The described embodiments and configurations leverage information provided to the UE, such as by a TCI status indicator and / or mobility trigger signaling. Such information may provide assistance that can facilitate the UE being able to communicate with the target cell without the UE needing to have a complete set of configuration information from the target network node. For example, it may be possible for the user equipment to implement an active TCI state of the target cell before the target cell activates the TCI state. The UE does not require that the TCI state to be applied at handover be pre-activated, i.e., the beam indication does not need to point to a candidate RRC configuration (before handover) that is not yet active. Such embodiments and configurations reduce UE implementation requirements and simplify the network signaling required to support mobility events.

[0164] Depending on various configurations, L1 / L2 mobility mechanisms may be implemented as described in more detail below.

[0165] According to one configuration, the UE may be configured to receive information, such as settings, regarding reference signals received by the UE from one or more network access nodes. The setting information may include at least one TCI state setting. The TCI state setting may include at least one TCI state associated with a cell other than the UE's serving cell, which cell may be supported by a target network node. According to one configuration, the UE may be configured to receive, from one or more network access nodes, an indication of information regarding reference signals received by the UE. The indication of information may include an indication of at least one TCI state setting to apply to communications (e.g., transmission and / or reception).

[0166] The UE may be configured to receive a trigger (which may include, for example, a command or an instruction) to switch to the new target cell. The trigger may be associated with a TCI state associated with the new target cell. The UE may be configured to determine, based on the provided TCI state setting, a downlink (DL) reference signal (RS) indicated by the TCI state or a QCL source RS (e.g., a synchronization signal block (SSB)) for the RS indicated by the TCI state.

[0167] The UE may perform this determination without needing to interpret or map the TCI state ID to a new target cell configuration because the TCI state ID was provided in the format of a source cell TCI state indicator. The UE may be configured to apply the determined DL RS to monitoring at least one downlink channel and / or transmitting at least one uplink channel. The UE may then be configured to consider, with respect to the target cell, that no TCI state indication has been provided and that no TCI state activation has been received. The UE may be configured to apply at least one rule of QCL assumption based on such consideration.

[0168] According to some embodiments, a UE may be configured to receive at least one indication of information regarding reference signals receivable by the UE from one or more network access nodes. The indication may include an indication of a TCI state configuration. The TCI state configuration may include at least one TCI state associated with a physical cell identity (PCI) other than the UE's serving cell. In one example, the UE may be configured with a TCI state including an SSB index associated with a cell having a PCI different from the serving cell. In one example, the UE may be configured with a TCI state including a CSI-RS index (with or without TRS information) associated with a cell having a PCI different from the serving cell.

[0169] To support the provision of such information to the UE, the network may be operable to (re)configure and provide new TCI configurations using tci-StatesToAddModList' and / or dl-OrJoint-TCIState (for Rel-17) defined in PDSCH-Config. This may also be referred to as unified TCI state configuration.

[0170] According to some implementations, the UE may be configured to receive a mobility trigger (e.g., a command, an indication, or a measurement) indicating that the UE should switch from a serving cell to a target cell. According to some embodiments, the trigger command may be associated with a TCI state associated with the target cell. According to some configurations, the UE may be provided with a TCI state associated with a cell having a different PCI than the serving cell, but simply providing a TCI state indication without a mobility trigger does not trigger a cell switch. In other words, the beam indication provided to the UE is "pending" receipt of a mobility trigger.

[0171] In one example, the UE may receive the configured TCI state ID (e.g., receive a configuration index and a TCI state ID) within a message that also includes the LTM trigger command. In one example, the UE may receive a beam indication, for example, via a MAC CE or a MAC CE and a DCI. In some examples, the UE may be configured to regard the beam indication as a cell switch command. In other words, in the MAC CE and DCI, or the MAC-CE, the signaling may include at least a configuration index, and the DCI may include a TCI state ID. According to some configurations, the TCI state ID received by the UE may include a reference to Rel-15, Rel-17, any other TCI state framework, or a framework that indicates a target cell beam indication. In some configurations, the UE may be configured to receive the configuration index (e.g., RRC configuration) and the QCL RS ID directly within the trigger command. According to some configurations, the UE may be configured to monitor the DL and / or UL channels of the new target cell using the QCL RS until it receives a new TCI activation / indication from the new target cell. In some examples, the UE may be configured to apply a beam indication (e.g., an indication of a TCI state) as a cell switch command. The beam indication may be provided by a DCI message or a MAC CE. The MAC CE or DCI indicating the beam may include a field indicating whether the beam indication is considered a mobility trigger by the user equipment. In one example, a UE configured to receive a beam indication considered a mobility trigger may determine a DL RS indicated by the TCI state or a QCL source RS (e.g., SSB) of the RS indicated by the TCI state. The UE may be configured to apply the determined DL RS to reception and / or transmission of at least one channel. The UE may be further configured to operate based on not receiving an indication of the TCI state regarding the target cell.

[0172] In some embodiments, the UE may be configured to determine the DL RS indicated by the TCI state or the QCL source RS (e.g., SSB) of the RS indicated by the TCI state. This determination may be made by the UE without interpreting or mapping the provided TCI state ID to a target cell configuration. According to one example, the UE may be configured to determine the DL RS or QCL source RS (typically SSB) indicated by the TCI state and utilize this as the QCL assumption for one or more channels. Furthermore, the UE may be configured to determine that the TCI state of the target cell (of the bandwidth portion BWP of the target cell) is not indicated.

[0173] According to one configuration, the reference signal included in, associated with, or indicated by the mobility trigger may be a reference signal listed in a network-configured list (of reference signals). In one example, the network may configure a node with a specific list, index, or mapping of reference signals that may be included in or indicated by the mobility trigger. As an example, the network may configure a mobility-trigger-specific reference signal list that may be indicated by at least one field in the mobility trigger. As an example of a list, the network may configure SSB#1...SSB#N (associated with a target cell PCI, such as PCI#1). The mobility trigger may include a reference signal indication (e.g., SSB#1...SSB#N). The indication may explicitly indicate a reference signal ID, such as SSB#1, using an SSB identifier. Alternatively, the mobility trigger may include a reference signal indication (e.g., SSB#1...SSB#N). The indication may explicitly indicate a reference signal ID using a logical index (e.g., index#1, index#2). As yet another example, if indexes SSB#1 and SSB#5 are configured, the logical indices of those SSBs are 0 and 1 (or 1 and 2, depending on the initial index). The UE may be configured to operate such that the reference signals indicated in the mobility trigger determine the monitoring and / or reception and / or transmission of at least one channel based on the reference signals. Alternatively (or additionally), the list of reference signals (identifiers) that may be included in the instruction included in the mobility trigger may be a list of reference signals configured for Layer 1 L1 reporting (e.g., Layer 1 reference signal received power L1-RSRP, Layer 1 signal interference and noise ratio L1-SINR, or any L1 reporting associated with or used in Layer 1 / Layer 2 mobility LTM). In one example, a configuration index value (indicating the target cell configuration) may be used to determine the PCI of the target cell, and the listed reference signals are associated with the PCI via the configuration index.Alternatively, the reference signal configuration may associate reference signals that can be indicated by (included in) a mobility trigger with a particular PCI. The list of reference signals that can be indicated by a mobility trigger may include a list of reference signals for one or more PCIs (i.e., a single list per candidate target cell or a single list for all target cells).

[0174] In some embodiments, the UE may be configured to apply the determined DL RS to monitoring at least one downlink channel and / or transmitting at least one uplink channel. In some configurations, after receiving a mobility trigger, the UE may be configured to assume information provided by a TCI status indicator (e.g., DL RS) as QCL information for at least one of the PDCCH, PDSCH, PUCCH, and PUSCH. In one configuration, if the code point indicates both DL and UL TCI states, the UE may be configured to apply QCL assumptions for the RS indicated by the DL and UL TCI states. In one configuration, if the code point indicates DL TCI states, the UE may be configured to apply QCL assumptions for the RS indicated by the DL and UL (channel) TCI states. In one configuration, if the code point indicates UL TCI states, the UE may be configured to apply QCL assumptions for the RS indicated by the DL and UL (channel) TCI states. In one configuration, if the code point indicates UL TCI states, the UE may be configured to apply QCL assumptions for the RS indicated by the DL and UL (channel) TCI states. In one configuration, the UE expects the mobility trigger to indicate a codepoint that indicates at least the downlink TCI state or the TCI state of both DL and UL (eg, joint TCI state).

[0175] In some embodiments, the UE may be configured to determine that a TCI state has not been directly provided and that activation of any TCI state has not been received with respect to the target cell. In some configurations, the UE may be configured to assume that a TCI state is not activated upon completing the RRC reconfiguration (i.e., when the handover is complete), but may maintain the QCL assumption for monitoring or transmitting on DL and UL channels until receiving a new activation or beam indication (TCI state indication) from the new target cell. In some configurations, the UE may be configured to apply at least one rule for determining the QCL assumption based on a determination that a TCI state has not been directly activated or indicated to the UE by the target cell.

[0176] In some configurations, when the MAC CE provides information regarding a mobility trigger to the UE (e.g., via a mobility trigger MAC CE) to trigger a cell switch, the information may include at least one field indicating whether the trigger command includes a TCI or DL ​​RS of the target cell. For example, this field may be identified by a configuration index. In some configurations, the configuration index may include an RRC configuration of the target cell. If the field in the MAC CE indicates that a TCI condition exists in the mobility trigger, the UE may be configured to operate as presented herein. If the field in the MAC CE indicates that a DL RS exists in the mobility trigger, the UE may be configured to operate as described herein and select to use a DL RS as a QCL source for at least one downlink and / or uplink channel. If the field in the MAC CE indicates that a TCI condition (or even a DL RS) does not exist in the mobility trigger, the UE may be configured to trigger a contention-based random access procedure for the target cell indicated by the configuration index. If the UE receives an indication of the TCI state of the target cell (e.g., if it is operating in inter-cell beam management but has not yet received a mobility trigger), the UE may be configured to use the currently indicated TCI state associated with the target cell to be effective for the methods described herein.

[0177] As one particular exemplary embodiment, consider a possible implementation of PDCCH monitoring: As described in [11, TS 38.321], for a CORESET other than the CORESET with index 0, either the UE is not provided with a TCI state configuration by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for that CORESET, or the UE is provided with an initial configuration of two or more TCI states by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for that CORESET, but the MAC address for one of those TCI states is not available. If no CE activation command has been received, the UE shall assume that the DM-RS antenna port associated with PDCCH reception is quasi-co-located with the SS / PBCH block identified by the UE during the initial access procedure or for the PUSCH transmission of the most recent configured grant as described in clause 19 for the same HARQ process, for the most recent CSI-RS or SSB for which TRS-info is configured (option 1) or associated with a PCI other than the serving cell provided to the UE as indicated by the TCI information, for the most recent CSI-RS or SSB index provided to the UE by a mobility trigger / LTM trigger command (or any message triggering a cell switch to a new target cell), or for the most recent CSI-RS or SSB index provided to the UE by a mobility trigger / LTM trigger command (or any message triggering a cell switch to a new target cell) in the serving cell (PCI) indicated by the configuration index (option 3).

[0178] For a CORESET other than the CORESET with index 0, the user equipment is not provided with a transmission configuration indicator state configuration by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for that CORESET, or is provided with an initial configuration of two or more transmission configuration indicator TCI states by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for that CORESET but has not received a MAC CE activate command for one of the TCI states; The user equipment For the most recently received channel status information reference signal CSI-RS or synchronization signal block SSB for which a tracking reference signal TRS-info is configured, associated with a physical cell identity PCI other than the serving cell provided to the user equipment indicated by the determined transmission configuration indicator TCI information, or optionally for the most recently received channel status information reference signal CSI-RS CSI-RS or synchronization signal block SSB index provided to the user equipment by a received configuration index provided by a mobility trigger or by a determination that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility as part of a Layer 1 / Layer 2 triggered mobility LTM trigger command, it is assumed that the synchronization signal / physical broadcast channel SS / PBCH block identified by the user equipment and the demodulation reference signal DM-RS antenna port associated with physical downlink control channel PDCCH reception are quasi-co-located. 10. The user equipment of claim 1, configured to:

[0179] In any of the embodiments herein, the mobility trigger (and any information it provides) may be provided by the MAC CE or the DCI.

[0180] Having described the general implementations and options, four specific examples will now be described in connection with the accompanying drawings.

[0181] For ease of understanding, throughout the specific examples, cells 20a and 20b may relate to the general 5G NR topology discussed above, as follows: cell 1 (20a) may be provided by DU1, etc., which may be connected to CU1, etc. Cell 20b may be such that, in the general case, cell 20b is provided by DU1, which may be connected to CU1, or cell 20b may be provided by DU2, which may be connected to CU1, or cell 20b may be provided by DU2, which may be connected to CU2, etc.

[0182] 3 is a signaling diagram illustrating signaling between a serving cell 20a and a UE 10, supporting one possible embodiment. A mobility event in which a cell change to cell 20b occurs is supported according to the following signaling steps. The steps shown in FIG. 3 may be performed in a different order, and as an example, step S5 may precede step S4. As an example, the UE may apply the determined RS / source RS to perform cell change-related signaling (e.g., RRC messages / MAC CE). Furthermore, the UE may continue to perform the actions presented in step S5 after step S4 occurs (i.e., after the cell change). S1: RRC signaling from the serving cell 20a is received at the UE, which configures the UE with L1 / L2 triggered mobility. S2: The serving cell provides a MAC CE to the UE 10 that triggers the UE's mobility to cell 2, 20b. The MAC CE contains either the TCI state or QCL source information for the UE with respect to the target cell 20b. S3: The UE is configured to determine a reference signal (RS) or source RS indicated by the TCI state provided in the MAC CE. S4: The UE 10, the serving cell 20a, and the target cell 20b perform a cell change. S5: The UE applies the determined RS to monitoring at least one downlink channel and / or transmitting at least one uplink channel from cell 2 (20b). S6: The UE is configured to assume that it does not have TCI state information for cell 2 20b (e.g., is not instructed to apply a TCI state). As a further example, the UE is configured to assume that no TCI state is indicated to apply to the communication (and continues to apply the determined RS to the communication).

[0183] 4 is a signaling diagram illustrating signaling between a serving cell 20a and a UE 10 supporting one possible implementation. A mobility event resulting in a cell change to a target cell 20b is supported according to the following signaling steps: T1: RRC signaling from the serving cell 20a is received at the UE, which configures the UE with L1 / L2 triggered mobility. T2: The serving cell provides a MAC CE mobility trigger to the UE 10 instructing the UE to change to cell 2, 20b. Since the MAC CE does not contain a TCI state or QCL source indicator, the UE has no information available about the target cell 20b. T3: The UE determines that the mobility trigger does not include the TCI state or the QCL source RS information. T4: The UE 10 is configured to recognize that performing a cell change will require a random access procedure to activate the transition to cell 2, 20b. T5: The UE is configured to send a random access request to the target serving cell 2.

[0184] 5 is a signaling diagram illustrating signaling between the serving cell 20a and the UE 10, supporting one possible embodiment. A mobility event in which a cell change to a target cell 20b occurs is supported according to the following signaling steps. The steps shown in FIG. 5 may be performed in a different order, and as an example, step U6 may precede step U5. As an example, the UE may apply the determined RS / source RS to perform cell change-related signaling (e.g., RRC messages / MAC CE). Furthermore, the UE may continue to perform the actions of U6 after U5 (i.e., after the cell change). U1: RRC signaling from the serving cell 20a is received at the UE, which configures the UE with L1 / L2 triggered mobility. U2: The serving cell provides a MAC CE including a beam indication related to cell 2 20b to the UE 10. The beam indication may include the TCI state or ICBM of cell 2. U3: The serving cell provides a MAC CE mobility trigger to the UE 10 instructing the UE to change to cell 2, 20b. This MAC CE does not include a TCI state or a QCL source indicator. U4: The UE 10 is configured to determine the RS of cell 2 or the source RS based on the TCI state in the ICBM. U5: The UE 10, the serving cell 20a, and the target cell 20b perform a cell change. U6: The UE applies the determined RS to monitoring at least one downlink channel and / or transmitting at least one uplink channel from cell 2 (20b). U7: The UE is configured to assume that it does not have TCI state information for cell 2 20b (e.g., it is not instructed to apply a TCI state). As a further example, the UE is configured to assume that no TCI state is indicated to apply to the communication (and continue to apply the determined RS to the communication).

[0185] FIG. 6 is a signaling diagram illustrating signaling between a serving cell 20a and a UE 10, supporting one possible implementation. A mobility event in which a cell change to a target cell 20b occurs is supported according to the following signaling steps. The steps shown in FIG. 6 may be performed in an order different from that shown. For example, step V7 may precede step V6. For example, the UE may apply the determined RS / source RS to perform cell change-related signaling (e.g., RRC messages / MAC CEs, etc.). Furthermore, the UE may continue to perform the actions of step V7 after step V6 (i.e., after the cell change). V1: RRC signaling from the serving cell 20a is received at the UE, which configures the UE with L1 / L2 triggered mobility. V2: The serving cell provides a MAC CE including a beam indication related to cell 2 20b to the UE 10. The beam indication may include the TCI state or ICBM of cell 2. V3: The UE 10 and Cell 2 communicate using the TCU state provided in V2 as the QCL assumption for monitoring. Cell 1 remains the serving cell. V4: The serving cell 20a provides the UE 10 with a MAC CE that triggers the UE's mobility to cell 2, 20b. This MAC CE contains either the TCI status or QCL source information for the UE with respect to the target cell 20b. V5: The UE 10 is configured to determine the RS of cell 2 or the source RS based on the TCI state to override the TCI state QCL assumption based on step V2. V6: The UE 10, the serving cell 20a, and the target cell 20b perform a cell change. V7: The UE applies the determined RS to monitoring at least one downlink channel and / or transmitting at least one uplink channel from cell 2 (20b). V8: The UE is configured to assume that it does not have TCI state information for cell 2 20b (e.g., it is not instructed to apply a TCI state). As a further example, the UE is configured to assume that no TCI state is indicated to apply to the communication (and continue to apply the determined RS to the communication).

[0186] Figure 7 is a flow chart illustrating steps according to one configuration. A UE according to the methodology shown in Figure 7 is configured to perform the following steps: 100: At least one TCI state configuration is received, and the TCI state is associated with a physical cell ID other than the UE serving cell. 200: Receive a cell switch trigger in the US, and the cell switch instructs the UE to switch to a new cell. 300: Determine whether the TCI state is associated with a cell switching trigger 400: Perform cell switching according to the determined association with the TCI state, and further determine at least one parameter of the associated TCI state to apply to further communication with the target cell.

[0187] The described embodiments and configurations leverage the information provided to the UE by the TCI state for communication with the target cell without the UE needing to have the target cell's TCI state active before the target cell activates the TCI state. The UE does not need pre-activated TCI states to be applied at handover, i.e., the beam indication does not need to point to a candidate RRC configuration that is not yet active (before handover). Such embodiments and configurations reduce UE implementation requirements and simplify the network signaling required to support mobility events.

[0188] Those skilled in the art will readily appreciate that the steps of the various methods described above can be performed by a programmed computer. Some embodiments herein are also intended to cover program storage devices, such as digital data storage media, that are machine- or computer-readable and that encode a program of machine-executable or computer-executable instructions, where the instructions perform some or all of the steps of the methods described above. The program storage device may be, for example, a digital memory, a magnetic storage medium, e.g., a magnetic disk and tape, a hard drive, or an optically readable digital data storage medium. Embodiments are also intended to cover computers programmed to perform the steps of the methods described above. The term non-transitory, as used herein, is not a limitation to the permanence of the data storage (e.g., RAM vs. ROM), but rather a limitation of the medium itself (i.e., tangible rather than a signal).

[0189] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) Hardware-only circuit implementations (e.g., analog and / or digital circuit implementations only) (b) A combination of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware; (ii) Any part of a software-enabled hardware processor (including a digital signal processor), software, and memory that work together to cause a device, such as a mobile phone or server, to perform various functions. (c) Hardware circuitry and / or processors, e.g., microprocessors or portions of microprocessors, that require software (e.g., firmware) to operate, but which may not be present if software is not necessary for operation.

[0190] This definition of circuit applies to all uses of the term in this application, including any claims. As a further example, as used in this application, the term circuit covers implementations of only a hardware circuit or processor(s), or of portions of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuit also covers, for example, baseband or processor integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or network devices, where applicable to certain claim elements.

[0191] While exemplary embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be understood that modifications to the examples provided can be made without departing from the scope of the invention as claimed.

[0192] The features set out in the foregoing description may be used in combinations other than those expressly set out.

[0193] Although functions have been described with reference to particular features, those functions may be performed by other functions whether or not described.

[0194] Although features have been described with reference to particular embodiments, those features may also be present in other embodiments whether or not described.

[0195] While the foregoing specification has attempted to draw attention to those features of the invention which are considered to be particularly important, it is to be understood that applicants claim protection for any patentable feature or combination of features referred to in this specification and / or shown in the drawings, whether or not specifically emphasized.

[0196] When referring to one or more network nodes, one of the one or more network nodes may be a network node supporting a serving cell to which the user equipment is connected.

[0197] When referring to a target network node, the target network node may be a network node that supports a target cell or a target candidate cell to switch to from the serving cell.

[0198] The network node supporting the serving cell and the network node supporting the target or target candidate cell may be the same node or different nodes, and both nodes may or may not be physically co-located.

[0199] When referring to a user equipment, the user equipment in response to detecting that the mobility trigger or the received reference signal configuration includes a configuration associated with or associable with a reference signal receivable from the target network node: Monitoring receivable reference signals from the target network node according to the detected associated configuration. The reference signal configuration may be part of the MAC CE beam indication ICBM, and the mobility trigger may be part of the MAC CE message.

[0200] the user equipment, in response to detecting that both the mobility trigger and the received reference signal configuration include a configuration associated with or associable with a reference signal receivable from the target network node, selects the most recently received configuration; Monitoring receivable reference signals from the target network node according to the detected associated configuration. It may be further configured as follows.

[0201] The user equipment may be further configured to perform a random access procedure to the target node in response to detecting that neither the mobility trigger nor the received reference signal configuration includes a configuration associated with or associable with a reference signal receivable from the target network node.

[0202] When referring to a switch of user equipment connection, such a switch may include a handover from a serving cell to a target cell, and the UE may or may not perform a random access procedure to perform the handover / switch, for example.

Claims

1. A user equipment of a radio access network, comprising: at least one processor; at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to: determining that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; receiving a reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network, the configuration may include a configuration of reference signals receivable from a target network node; receiving a mobility trigger indicating that the user equipment should switch to the target network node, the mobility trigger may include a configuration associated with a reference signal receivable from the target network node; switching to the target network node; evaluating whether the mobility trigger or the received reference signal configuration includes a configuration associated with a reference signal receivable from the target network node, and if so, monitoring the reference signals receivable from the target network node in accordance with the evaluated associated configuration; At least one memory for executing A user equipment comprising:

2. The user equipment: assuming that after the switching to the target network node, a reference signal configuration associated with reference signals receivable from the target network node is unknown. The user equipment of claim 1 , further comprising:

3. 3. The user equipment of claim 2, wherein the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a transmission configuration indicator state, the configuration comprising a transmission configuration indicator state of reference signals receivable from the target network node, and wherein after the switching to the target network node, the user equipment is configured not to apply the transmission configuration indicator state of the reference signals receivable from the target network node that were received before the switching to the target network node.

4. If the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a configuration for reference signals receivable from a target network node, the user equipment: monitoring the reference signals receivable from the target network node in accordance with the evaluated associated configuration at least until the mobility trigger is received. A user equipment according to any one of claims 1 to 3, configured to execute:

5. 4. The user equipment of claim 1, wherein evaluating whether the reference signal configuration associated with a reference signal or a mobility trigger includes a configuration for a reference signal receivable from the target network node comprises selecting the reference signal configuration associated with a reference signal receivable from the target network node received in the mobility trigger in preference to any reference signal configuration associated with a reference signal receivable from the target network node included in the reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network.

6. If the user equipment evaluates that none of the reference signal configurations and mobility triggers associated with reference signals receivable from one or more network nodes of the radio access network include a reference signal configuration associated with reference signals receivable from the target network node, the user equipment: initiating a random access request to the target network node indicated by the mobility trigger. A user equipment according to any one of claims 1 to 3, configured to execute:

7. 7. The user equipment according to claim 1, wherein the user equipment is configured to monitor reference signals receivable from one or more network nodes of the radio access network in accordance with the evaluated associated configuration at least until updated reference signal configurations associated with the reference signals receivable from the target network node are received from the target network node.

8. 8. The user equipment of claim 1, wherein monitoring the reference signals receivable from the target network node in accordance with the evaluated associated configuration comprises monitoring at least one downlink channel received from the target network node based on the reference signals receivable from the target.

9. 9. The user equipment according to claim 1, wherein the user equipment is configured to perform transmissions based on the evaluated associated target cell configuration at least until updated reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network are received from the target network node.

10. The user equipment of claim 9 , wherein the transmitting comprises transmitting at least one uplink channel based on the reference signal receivable from the target.

11. The user equipment of any one of claims 1 to 10, wherein the reference signal configuration associated with reference signals receivable from a target cell of the radio access network includes at least one inter-cell beam management ICBM indicator.

12. 12. A user equipment according to any one of claims 1 to 11, wherein the reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises at least one transmission configuration indicator TCI status indicator.

13. The user equipment of claim 12 , wherein the user equipment is configured to determine a downlink reference signal or a quasi-co-located source reference signal depending on a received transmission configuration indicator state.

14. 14. The user equipment of claim 12 or 13, wherein the user equipment is configured with at least one transmission configuration indicator state that is mapped to a downlink reference signal index associated with the target network node.

15. The user equipment: receiving a transmission configuration indicator state index that maps a reference signal to a transmission configuration indicator state, the index being determined by the network; A user equipment according to any one of claims 12 to 14, configured to execute:

16. The user equipment of any one of claims 1 to 15, wherein the mobility trigger comprises a switching command or switching parameters to be satisfied in relation to the target network node.

17. The user equipment of any one of claims 1 to 16, wherein the mobility trigger comprises a medium access control layer control element MAC-CE or downlink control information DCI receivable by the user equipment.

18. The user equipment of any one of claims 1 to 17, wherein the mobility trigger comprises a transmission configuration indicator TCI state that is mapped to a reference signal index associated with the target network node.

19. The user equipment of any one of claims 1 to 18, wherein the mobility trigger comprises a downlink reference signal configuration associated with the target network node.

20. receiving a reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network, receiving at least one transmission configuration indicator TCI state, wherein the at least one configuration of reference signals receivable from a target network node comprises a transmission configuration indicator TCI state associated with a physical cell identity different from a serving cell of the user equipment; receiving a mobility trigger indicating that the user equipment switches to the target network node, the mobility trigger being associated with a transmission configuration indicator (TCI) state associated with the target network node; wherein the user equipment comprises: determining a downlink reference signal indicated by the transmission configuration indicator TCI state or a quasi-colocated source reference signal of the reference signal indicated by the transmission configuration indicator TCI state without mapping the transmission configuration indicator TCI state to the target cell configuration; switching to the target network node; monitoring at least one downlink channel and, optionally, applying the determined downlink reference signal to transmit at least one uplink channel; assessing that the user equipment does not have a transmission configuration indicator TCI state with respect to the target cell and applying at least one rule of quasi-co-located assumption based on the applied reference signal; The user equipment of claim 1 configured to execute:

21. For a CORESET other than the CORESET with index 0, the user equipment is not provided with a transmission configuration indicator state configuration by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for the CORESET, or is provided with an initial configuration of two or more transmission configuration indicator TCI states by tci-StatesPDCCH-ToAddList and tci-StatesPDCCH-ToReleaseList for the CORESET but has not received a MAC CE activation command for one of the TCI states; The user equipment: or optionally, for a most recently received channel status information reference signal CSI-RS or synchronization signal block SSB for which a tracking reference signal TRS-info is configured, associated with a physical cell identity PCI other than the serving cell provided to said user equipment indicated by the determined transmission configuration indicator TCI information; on the most recent channel status information reference signal CSI-RS or synchronization signal block SSB index provided to the user equipment by a received configuration index provided by the mobility trigger or by a decision that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility as part of a Layer 1 / Layer 2 triggered mobility LTM trigger command or equivalent message triggering a cell switch to a new target cell, or optionally with respect to the most recent channel status information reference signal CSI-RS or synchronization signal block SSB index provided to the user equipment by the mobility trigger or by a decision that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility as part of a Layer 1 / Layer 2 triggered mobility LTM trigger command from the user equipment's serving cell indicated by a configuration index or in any message triggering a cell switch to the target cell, It is assumed that the synchronization signal / physical broadcast channel SS / PBCH block identified by the user equipment and the demodulation reference signal DM-RS antenna port associated with physical downlink control channel PDCCH reception are quasi-co-located. The user equipment of claim 1 configured to:

22. the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network do not include a configuration of reference signals receivable from a target network node; The received mobility trigger indicating that the user equipment should switch to the target network node comprises configuring reference signals receivable from the target network node, and the user equipment: switching to the target network node; monitoring the reference signals receivable from the target network node according to the configuration of the reference signals receivable from the target network node included in the received mobility trigger; The user equipment of claim 1 ,

23. the user equipment is connected to a serving cell; the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network is received from the serving cell and does not include a configuration of reference signals receivable from a target network node; The received mobility trigger comprises a Medium Access Control Layer Control Element (MAC CE) message from the serving cell indicating that the user equipment switches to the target network node, and comprises a configuration of reference signals receivable from the target network node in the form of a transmission configuration indicator (TCI) state or quasi-colocated QCL source information related to a target cell, wherein the user equipment: determining a reference signal or source reference signal indicated by the TCI state or quasi-colocated QCL source information; switching to the target network node; - monitoring at least one downlink channel and, optionally, at least one uplink channel by applying the determined reference signal to transmit the reference signal receivable from the target network node; and the user equipment is adapted to execute - regarding the target cell as not having an indicated transmission configuration indicator TCI state. The user equipment of claim 1 ,

24. the received reference signal configurations associated with reference signals receivable from one or more network nodes of the radio access network do not include a configuration of reference signals receivable from a target network node; The received mobility trigger indicating that the user equipment should switch to the target network node does not include a configuration of reference signals receivable from the target network node, and the user equipment: determining to switch to the target network node; initiating a random access request to a target cell; The user equipment of claim 1 ,

25. the user equipment is connected to a serving cell; the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network is received from the serving cell and does not include a configuration of reference signals receivable from a target network node; the received mobility trigger comprises a Medium Access Control Layer Control Element (MAC CE) message from the serving cell indicating that the user equipment switches to the target network node, but does not comprise a configuration of reference signals receivable from the target network node, and the user equipment: determining to switch to the target network node; initiating a contention-based random access request to a target cell; The user equipment of claim 1 ,

26. the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a configuration of reference signals receivable from a target network node; The received mobility trigger indicating that the user equipment should switch to the target network node does not include a configuration of reference signals receivable from the target network node, and the user equipment: switching to the target network node; monitoring reference signals receivable from the target network node according to the configuration of reference signals receivable from the target network node contained in the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network; The user equipment of claim 1 ,

27. the user equipment is connected to a serving cell; the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a medium access control layer control element (MAC CE) message from the serving cell, and comprises a transmission configuration indicator (TCI) state or an inter-cell beam management (ICBM) indication associated with a target cell; The received mobility trigger comprises a Medium Access Control Layer Control Element (MAC CE) message from the serving cell indicating that the user equipment switches to the target network node, and the received mobility trigger does not comprise a configuration of reference signals receivable from the target network node, and the user equipment: determining the reference signal or source reference signal indicated by the received transmission configuration indicator TCI status or inter-cell beam management ICBM indication; switching to the target network node; monitoring the determined reference signal receivable from the target network node by monitoring at least one downlink channel and, optionally, applying the determined reference signal to transmit at least one uplink channel; and the user equipment is adapted to execute - regarding the target cell as not having an indicated transmission configuration indicator TCI state. The user equipment of claim 1 ,

28. the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a configuration of reference signals receivable from a target network node; the user equipment is caused to leave its serving cell unchanged and to communicate with a target cell using the received configuration of reference signals receivable from a target network node; The received mobility trigger indicating that the user equipment should switch to the target network node comprises configuring reference signals receivable from the target network node, and the user equipment: switching to the target network node; monitoring the reference signals receivable from the target network node according to the configuration of the reference signals receivable from the target network node included in the received mobility trigger; The user equipment of claim 1 ,

29. the user equipment is connected to a serving cell; the received reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network comprises a medium access control layer control element (MAC CE) message from the serving cell, and comprises a transmission configuration indicator (TCI) state or an inter-cell beam management (ICBM) indication associated with a target cell; The user equipment: communicating with the target cell using the received transmission configuration indicator TCI state as a pseudo-co-location assumption for monitoring the target cell while maintaining the serving cell; and The received mobility trigger comprises a Medium Access Control Layer Control Element (MAC CE) message from the serving cell indicating that the user equipment switches to the target network node, and comprises a configuration of reference signals receivable from the target network node in the form of a transmission configuration indicator (TCI) state or quasi-colocated QCL source information related to the target cell, wherein the user equipment: determining a reference signal or source reference signal indicated by the transmission configuration indicator TCI state or quasi-colocated QCL source information included in the received mobility trigger to overwrite the previous transmission configuration indicator TCI state or quasi-colocated QCL assumption; switching to the target network node; - monitoring at least one downlink channel and, optionally, at least one uplink channel by applying the determined reference signal to transmit the reference signal receivable from the target network node; and the user equipment is adapted to execute - regarding the target cell as not having an indicated transmission configuration indicator TCI state. The user equipment of claim 1 ,

30. 1. A method performed by a user equipment of a radio access network, comprising: determining that the user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; receiving a reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network, the configuration may include a configuration of reference signals receivable from a target network node; receiving a mobility trigger indicating that the user equipment should switch to the target network node, the mobility trigger may include a configuration associated with a reference signal receivable from the target network node; switching to the target network node; evaluating whether the mobility trigger or the received reference signal configuration includes a configuration associated with a reference signal receivable from the target network node, and if so, monitoring the reference signals receivable from the target network node in accordance with the evaluated associated configuration; A method comprising:

31. A computer program product operable to perform the method of claim 30 when executed on a computer.

32. A network node of a radio access network, comprising: at least one processor; at least one memory storing instructions that, when executed by the at least one processor, cause the user equipment to: determining that a user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; providing to the user equipment a reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network, the configuration may include a configuration of reference signals receivable from a target network node; providing a mobility trigger to the user equipment indicating that the user equipment should switch to the target network node, the mobility trigger may include a configuration associated with a reference signal receivable from the target network node; At least one memory for executing A network node comprising:

33. 1. A method performed by a network node of a radio access network, comprising: determining that a user equipment is configured to apply Layer 1 or Layer 2 triggered mobility; providing to the user equipment a reference signal configuration associated with reference signals receivable from one or more network nodes of the radio access network, the configuration may include a configuration of reference signals receivable from a target network node; providing a mobility trigger to the user equipment indicating that the user equipment should switch to the target network node, the mobility trigger may include a configuration associated with a reference signal receivable from the target network node; A method comprising:

34. 34. A computer program product operable to perform the method of claim 33 when executed on a computer.

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