Low layer mobility release provisioning

Abstract

There is provided an apparatus comprising means for: determining, at a distributed unit of a serving node of a user equipment, that a release condition for a target cell prepared for low-layer mobility of the user equipment is satisfied; and in response to determining that the release condition is satisfied, releasing the target cell, and an apparatus comprising means for: determining a release condition for at least one cell prepared for low-layer mobility of a user equipment; and providing an indication of the release condition to a distributed element of the serving node of the user equipment.

Description

Technical Field

[0001] The present application relates to methods, apparatus, systems and computer programs and particularly, but not exclusively, to low layer mobility (LLM) release preparation. Background Art

[0002] A communication system may be viewed as a facility for enabling communication sessions between two or more entities, such as user terminals, base stations, and / or other nodes, by providing carrier waves between the various entities involved in the communication path. A communication system may be provided, for example, by a communication network and one or more compatible communication devices. A communication session may include, for example, data communications for carrying communications such as voice, video, electronic mail (email), text messaging, multimedia, and / or content data. Non-limiting examples of the services provided include two-way or multi-way calls, data communications or multimedia services, and access to data network systems such as the Internet.

[0003] In a wireless communication system, at least a portion of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems include public land mobile networks (PLMNs), satellite-based communication systems, and different wireless local area networks, such as wireless local area networks (WLANs). Some wireless systems can be divided into cells and are therefore often referred to as cellular systems.

[0004] A user may access a communication system through an appropriate communication device or terminal. A user's communication device may be referred to as user equipment (UE) or user equipment. The communication device is provided with appropriate signal receiving and sending means for enabling communication, such as enabling access to a communication network or communicating directly with other users. The communication device may access a carrier provided by a station (e.g., a base station of a cell) and send and / or receive communications on the carrier.

[0005] A communication system and associated equipment typically operate according to a given standard or specification, which sets out what the various entities associated with the system are allowed to do and how this should be achieved. The communication protocols and / or parameters that will be used for the connection are also typically defined. An example of a communication system is UTRAN (3G radio). Other examples of communication systems are the Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio access technology and the so-called 5G or New Radio (NR) networks. NR is standardized by the Third Generation Partnership Project (3GPP). Summary of the invention

[0006] In a first aspect, an apparatus is provided, comprising components for: determining, at a distributed unit of a serving node of a user equipment, that a release condition for a target cell prepared for low-layer mobility of the user equipment is satisfied; and causing the target cell to be released in response to determining that the release condition is satisfied.

[0007] The means for causing the target cell to be released may include means for providing an indication to the central unit indicating preparation for release of the target cell.

[0008] The indication to the central unit may include an identifier of the target cell or a low layer mobility preparation identifier.

[0009] The apparatus may include means for: receiving at least one layer 1 measurement value from a user equipment at a distributed unit of a serving node; and determining, based on the at least one layer 1 measurement value, that a release condition for a target cell is met.

[0010] The means for causing the target cell to be released may include means for providing an indication to the user equipment to release the configuration of the target cell.

[0011] The indication to the user equipment may be provided in a layer 1 message.

[0012] The layer 1 message may include a medium access control element MAC CE or a downlink control information DCI indication.

[0013] The indication to the user equipment may include an indication of whether layer 1 measurements for the target cell should be continued.

[0014] The indication to the user equipment may include an identifier of the target cell or a low layer mobility preparation identifier.

[0015] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0016] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0017] The apparatus may comprise means for receiving an indication of a release condition at a distributed unit of a serving node from a central unit.

[0018] In a second aspect, a method is provided, comprising: determining, at a distributed unit of a service node of a user equipment, that a release condition for a target cell prepared for low-layer mobility of the user equipment is satisfied; and causing the target cell to be released in response to determining that the release condition is satisfied.

[0019] Causing the target cell to be released may include providing an indication to the central unit indicating release preparation of the target cell.

[0020] The indication to the central unit may include an identifier of the target cell or a low layer mobility preparation identifier.

[0021] The method may include: receiving at a distributed unit of a serving node at least one layer 1 measurement value from a user equipment; and determining, based on the at least one layer 1 measurement value, that a release condition for a target cell is met.

[0022] Causing the target cell to be released may include providing an indication to the user equipment to release the configuration of the target cell.

[0023] The indication to the user equipment may be provided in a layer 1 message.

[0024] The layer 1 message may include a medium access control element MAC CE or a downlink control information DCI indication.

[0025] The indication to the user equipment may include an indication of whether layer 1 measurements for the target cell should be continued.

[0026] The indication to the user equipment may include an identifier of the target cell or a low layer mobility preparation identifier.

[0027] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0028] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0029] The method may include receiving an indication of a release condition at a distributed unit of a serving node from a central unit.

[0030] In a third aspect, a device is provided, comprising: at least one processor and at least one memory, the at least one memory storing instructions, which when executed by the at least one processor causes the device to at least: determine, at a distributed unit of a service node of a user equipment, that a release condition for a target cell prepared for low-layer mobility of the user equipment is satisfied; and in response to determining that the release condition is satisfied, cause the target cell to be released.

[0031] The apparatus may be configured to provide an indication to the central unit indicating release preparation of the target cell.

[0032] The indication to the central unit may include an identifier of the target cell or a low layer mobility preparation identifier.

[0033] The apparatus may be configured to: receive at least one layer 1 measurement value from a user equipment at a distributed unit of a serving node; and determine, based on the at least one layer 1 measurement value, that a release condition for a target cell is met.

[0034] The apparatus may be configured to provide an indication to the user equipment to release the configuration of the target cell.

[0035] The indication to the user equipment may be provided in a layer 1 message.

[0036] The layer 1 message may include a medium access control element MAC CE or a downlink control information DCI indication.

[0037] The indication to the user equipment may include an indication of whether layer 1 measurements for the target cell should be continued.

[0038] The indication to the user equipment may include an identifier of the target cell or a low layer mobility preparation identifier.

[0039] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0040] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0041] The apparatus may be configured to receive an indication of a release condition from the central unit at a distributed unit of the serving node.

[0042] In a fourth aspect, a computer readable medium is provided, the computer readable medium comprising instructions, which when executed by an apparatus causes the apparatus to at least perform the following: At a distributed unit of a serving node of the user equipment, determining that a release condition for a target cell prepared for low layer mobility of the user equipment is satisfied; and causing the target cell to be released in response to determining that the release condition is satisfied.

[0043] Causing the target cell to be released may include providing an indication to the central unit indicating release preparation of the target cell.

[0044] The indication to the central unit may include an identifier of the target cell or a low layer mobility preparation identifier.

[0045] The apparatus may be caused to perform: receiving at a distributed unit of a serving node at least one layer 1 measurement value from a user equipment; and determining, based on the at least one layer 1 measurement value, that a release condition for a target cell is met.

[0046] Causing the target cell to be released may include providing an indication to the user equipment to release the configuration of the target cell.

[0047] The indication to the user equipment may be provided in a layer 1 message.

[0048] The layer 1 message may include a medium access control element MAC CE or a downlink control information DCI indication.

[0049] The indication to the user equipment may include an indication of whether layer 1 measurements for the target cell should be continued.

[0050] The indication to the user equipment may include an identifier of the target cell or a low layer mobility preparation identifier.

[0051] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0052] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0053] The apparatus may be caused to perform: receiving, at a distributed unit of the service node from the central unit, an indication of a release condition.

[0054] In a fifth aspect, a non-transitory computer-readable medium is provided, the non-transitory computer-readable medium comprising program instructions for causing an apparatus to at least perform the method according to the second aspect.

[0055] In a sixth aspect, an apparatus is provided, the apparatus comprising means for determining a release condition for at least one cell prepared for low layer mobility of a user equipment; and providing an indication of the release condition to a distributed unit of a serving node of the user equipment.

[0056] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0057] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0058] The apparatus may comprise means for providing a measurement configuration to a user equipment to enable evaluation of a release condition.

[0059] The apparatus may include means for providing an indication of the release condition to the user equipment.

[0060] The apparatus may include means for determining a release condition based on at least one of a reference signal received power threshold, a serving node associated with a target cell, a total number of cells prepared for user equipment, and a load condition of a serving node associated with the target cell.

[0061] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0062] The target cell may be associated with the distributed unit or a further distributed unit.

[0063] In a seventh aspect, an apparatus is provided, the apparatus comprising means for receiving, at a distributed unit of a serving node of a user equipment from a central unit, an indication of a release condition for at least one cell prepared for low layer mobility of the user equipment.

[0064] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0065] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0066] The release condition may be determined based on at least one of: a reference signal received power threshold, a serving node associated with the target cell, a total number of cells prepared for the user equipment, and a load condition of a serving node associated with the target cell.

[0067] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0068] The target cell may be associated with the distributed unit or a further distributed unit.

[0069] In an eighth aspect, a method is provided, the method comprising: determining a release condition for at least one cell prepared for low layer mobility of a user equipment; and providing an indication of the release condition to a distributed unit of a serving node of the user equipment.

[0070] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0071] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0072] The method may comprise providing a measurement configuration to a user equipment to enable evaluation of a release condition.

[0073] The method may comprise providing an indication of the release condition to the user equipment.

[0074] The method may include determining the release condition based on at least one of: a reference signal received power threshold, a serving node associated with the target cell, a total number of cells prepared for the user equipment, and a load condition of the serving node associated with the target cell.

[0075] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0076] The target cell may be associated with the distributed unit or a further distributed unit.

[0077] In a ninth aspect, a method is provided, the method comprising: receiving, at a distributed unit of a serving node of a user equipment from a central unit, an indication of a release condition for at least one cell prepared for low layer mobility of the user equipment.

[0078] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0079] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0080] The release condition may be determined based on at least one of: a reference signal received power threshold, a serving node associated with the target cell, a total number of cells prepared for the user equipment, and a load condition of a serving node associated with the target cell.

[0081] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0082] The target cell may be associated with the distributed unit or a further distributed unit.

[0083] In a tenth aspect, a device is provided, comprising: at least one processor and at least one memory, the at least one memory storing instructions, which when executed by the at least one processor causes the device to at least: determine a release condition for at least one cell prepared for low-layer mobility of a user equipment; and provide an indication of the release condition to a distributed unit of a service node of the user equipment.

[0084] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0085] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0086] The apparatus may be caused to provide a measurement configuration to a user equipment to enable evaluation of the release condition.

[0087] The apparatus may be caused to provide an indication of the release condition to the user equipment.

[0088] The apparatus may be caused to determine the release condition based on at least one of: a reference signal received power threshold, a serving node associated with the target cell, a total number of cells prepared for the user equipment, and a load condition of a serving node associated with the target cell.

[0089] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0090] The target cell may be associated with the distributed unit or a further distributed unit.

[0091] In an eleventh aspect, a device is provided, comprising: at least one processor and at least one memory, the at least one memory storing instructions, which when executed by the at least one processor causes the device to at least: receive, at a distributed unit of a service node of a user equipment, from a central unit an indication of a release condition for at least one cell prepared for low-layer mobility of the user equipment.

[0092] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0093] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0094] The release condition may be determined based on at least one of: a reference signal received power threshold, a serving node associated with the target cell, a total number of cells prepared for the user equipment, and a load condition of a serving node associated with the target cell.

[0095] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0096] The target cell may be associated with the distributed unit or a further distributed unit.

[0097] In a twelfth aspect, a computer readable medium is provided, the computer readable medium comprising instructions, which when executed by an apparatus causes the apparatus to at least perform the following: Determining a release condition for at least one cell prepared for low layer mobility of the user equipment; and providing an indication of the release condition to a distributed unit of a serving node of the user equipment.

[0098] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0099] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0100] The apparatus may be caused to provide a measurement configuration to a user equipment to enable evaluation of the release condition.

[0101] The apparatus may be caused to provide an indication of the release condition to the user equipment.

[0102] The apparatus may be caused to determine the release condition based on at least one of: a reference signal received power threshold, a serving node associated with the target cell, a total number of cells prepared for the user equipment, and a load condition of a serving node associated with the target cell.

[0103] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0104] The target cell may be associated with the distributed unit or a further distributed unit.

[0105] In a thirteenth aspect, a computer readable medium is provided, the computer readable medium comprising instructions, which when executed by an apparatus causes the apparatus to at least perform the following: An indication of a release condition for at least one cell prepared for low layer mobility of the user equipment is received from a central unit at a distributed unit of a serving node of the user equipment.

[0106] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load.

[0107] The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

[0108] The release condition may be determined based on at least one of: a reference signal received power threshold, a serving node associated with the target cell, a total number of cells prepared for the user equipment, and a load condition of a serving node associated with the target cell.

[0109] The release condition may be the same or different for each of the plurality of cells prepared for low layer mobility of the user equipment.

[0110] The target cell may be associated with the distributed unit or a further distributed unit.

[0111] In a fourteenth aspect, a non-transitory computer-readable medium is provided, the non-transitory computer-readable medium comprising program instructions for causing an apparatus to at least execute the method according to the eighth aspect or the ninth aspect.

[0112] In the above, many different embodiments have been described. It should be understood that other embodiments can be provided by combining any two or more of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0113] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0114] Figure 1 A schematic diagram of an example 5GS communication system is shown;

[0115] Figure 2 A schematic diagram of an example mobile communication device is shown;

[0116] Figure 3 A schematic diagram of an example control device is shown;

[0117] Figure 4 A signaling diagram showing an example L1 / 2 inter-cell mobility procedure;

[0118] Figure 5 A signaling diagram illustrating an example release procedure for LLM mobility;

[0119] Figure 6 A flow chart showing a method according to an example embodiment is shown;

[0120] Figure 7 A flow chart showing a method according to an example embodiment is shown;

[0121] Figure 8 A signaling flow of a method according to an example embodiment is shown. DETAILED DESCRIPTION

[0122] Before explaining the examples in detail, refer to Figures 1 to 3 Certain general principles of wireless communication systems and mobile communication devices are briefly explained to aid understanding of the technology on which the described examples are based.

[0123] An example of a suitable communication system is the 5G or NR concept. The network architecture in NR may be similar to that of Advanced LTE. The base station of the NR system may be referred to as the next generation Node B (gNB). Changes to the network architecture may depend on the need to support various radio technologies and more sophisticated QoS support, as well as some on-demand requirements for quality of service (QoS) levels such as supporting user's quality of experience (QoE). Network-aware services and applications, as well as service and application-aware networks, may also bring changes to the architecture. These involve information-centric networks (ICNs) and user-centric content distribution networks (UC-CDN) approaches. NR may use multiple-input multiple-output (MIMO) antennas, many more base stations or nodes than LTE (the so-called small cell concept), including macro sites that operate in collaboration with smaller stations, and may also employ various radio technologies to obtain better coverage and enhanced data rates.

[0124] Future networks may utilize network function virtualization (NFV), which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that can be operably connected or linked together to provide services. Virtualized network functions (VNFs) may include one or more virtual machines that use standard or general-purpose servers rather than custom hardware to run computer program code. Cloud computing or data storage may also be utilized. In radio communications, this may mean performing node operations at least in part in a server, host, or node that is operably coupled to a remote radio head. Node operations may also be distributed among multiple servers, nodes, or hosts. It should also be understood that the labor distribution between core network operations and base station operations may be different from that of LTE or even non-existent.

[0125] Figure 1 A schematic representation of a 5G system (5GS) 100 is shown. The 5GS may include a user equipment (UE) 102 (which may also be referred to as a communication device or terminal), a 5G radio access network (5GRAN) 104, a 5G core network (5GCN) 106, one or more application functions (AFs) 108, and one or more data networks (DNs) 110.

[0126] An example 5G core network (CN) includes functional entities. The 5GCN 106 may include one or more access and mobility management functions (AMFs) 112, one or more session management functions (SMFs) 114, an authentication server function (AUSF) 116, a unified data management (UDM) 118, one or more user plane functions (UPFs) 120, a unified data repository (UDR) 122, and / or a network exposure function (NEF) 124. The UPF is controlled by the SMF (session management function) which receives policies from the PCF (policy control function).

[0127] The CN is connected to the UE via a radio access network (RAN). The 5G RAN may include one or more gNodeB (GNB) distributed unit functions connected to one or more gNodeB (GNB) central unit functions. The RAN may include one or more access nodes.

[0128] The user plane function (UPF) called PDU Session Anchor (PSA) can be responsible for forwarding frames back and forth between the DN and the tunnel established over 5G to the UE exchanging services with the DN.

[0129] Now refer to Figure 2 describing in more detail possible mobile communication devices, Figure 2A schematic partial cutaway view of a communication device 200 is shown. Such a communication device is generally referred to as a user equipment (UE) or terminal. Suitable mobile communication devices can be provided by any device capable of sending and receiving radio signals. Non-limiting examples include a mobile station (MS) or mobile device (such as a mobile phone or so-called 'smart phone'), a computer provided with a wireless interface card or other wireless interface facilities (e.g., a USB software dog), a personal data assistant (PDA) or a tablet computer provided with wireless communication capabilities, a voice over IP (VoIP) phone, a portable computer, a desktop computer, an image capture terminal device (such as a digital camera), a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), an intelligent device, a wireless customer premises equipment (CPE) or any combination of these, etc. The mobile communication device can provide, for example, data communications for carrying communications such as voice, email (email), text messages, multimedia, etc. Therefore, users can be given and provided with many services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communications or multimedia services, or simply access to a data communications network system, such as the Internet. Broadcast or multicast data may also be provided to the user. Non-limiting examples of content include downloads, television and radio programs, videos, advertisements, various alerts, and other information.

[0130] The mobile device is typically provided with at least one data processing entity 201, at least one memory 202 and possibly other components 203 for software and hardware assisted execution of the tasks it is designed to perform, including control of access to and communication with access systems and other communication devices. The data processing, storage and other related control devices may be provided on appropriate circuit boards and / or in chipsets. This feature is indicated by reference numeral 204. The user may control the operation of the mobile device by means of a suitable user interface (e.g., a keypad 205, voice commands, a touch-sensitive screen or pad, a combination thereof, etc.). A display 208, a speaker and a microphone may also be provided. In addition, the mobile communication device may include appropriate connectors (wired or wireless) to other devices and / or for connecting external accessories (e.g., a hands-free device) to other devices.

[0131] The mobile device 200 may receive signals via an air or radio interface 207 via appropriate means for receiving, and may transmit signals via appropriate means for transmitting radio signals. Figure 2 In the embodiment of the present invention, the transceiver arrangement is schematically designated by block 206. The transceiver arrangement 206 may be provided, for example, by a radio component and an associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

[0132] Figure 3An example of a control device 300 for a communication system is shown, which communication system is, for example, to be coupled to and / or used to control a station of an access system, such as a RAN node (e.g., a base station, eNB or gNB), a relay node or a core network node (such as an MME or S-GW or P-GW), or a core network function (such as an AMF / SMF), or a server or host. The method can be implemented in a single control device or across more than one control device. The control device can be integrated with a node or module of the core network or RAN or external to it. In some embodiments, the base station includes a separate control device unit or module. In other embodiments, the control device can be other network elements, such as a radio network controller or a spectrum controller. In some embodiments, each base station can have such a control device and a control device provided in a radio network controller. The control device 300 can be arranged to provide control of communications in a service area of ​​the system. The control device 300 includes at least one memory 301, at least one data processing unit 302, 303 and an input / output interface 304. Via the interface, the control device can be coupled to a receiver and a transmitter of the base station. The receiver and / or the transmitter may be implemented as a radio front end or a remote radio head.

[0133] L1 / 2 inter-cell mobility is one of the upcoming targets for mobility enhancement in Rel.18. In the L3 mobility procedure, the handover (HO) between two cells is decided by the Radio Resource Control (RRC) layer. In contrast, L1 / 2 inter-cell mobility is performed by the Medium Access Control (MAC) layer terminated in the Distributed Unit (DU). L1 / 2 inter-cell mobility can also be referred to as low or lower layer mobility (LLM).

[0134] Figure 4 An example signaling diagram for L1 / 2 inter-cell mobility from a serving cell in DU1 to a target cell in DU2 (inter-DU intra-central unit (CU) scenario) is shown. The same diagram will also apply in the case of intra-DU intra-CU cell change, where DU1 is identical to DU2.

[0135] In step 1, the UE sends a measurement report containing cell quality measurements of the serving cell and neighboring cells. The UE may be configured by the serving cell to send measurement reports when the UE still has a good connection to the serving cell.

[0136] At step 2, DU1 sends a measurement report to CU.

[0137] Using the reported cell quality measurements, the CU identifies a potential set of candidate target cells that the UE can switch to. In this example, the CU identifies a candidate target cell served by DU1 (which also controls the serving DU / cell) and another DU2 controlled by the same CU.

[0138] In step 3: CU requests to prepare a candidate target cell controlled by DU1 by sending a UE context establishment request message to DU1.

[0139] In step 4, DU1 provides the UE's configuration in a UE Context Setup Response message containing a container from the DU to the CU.

[0140] To prepare the target cell controlled by DU2, the same steps 3 and 4 as steps 5 / 6 of DU2 are performed.

[0141] After receiving the UE configuration for the candidate target cell, the CU generates an RRC reconfiguration that is sent to the UE in step 8. Among other information, the RRC reconfiguration message contains the measurement reporting configuration for L1 / 2 handover, i.e., the configuration on how to report the L1 beam measurement of the serving cell and the target cell in step 10, and the configuration of the prepared candidate cells that the UE needs to perform when the UE receives a MAC Control Element (CE) command to change the serving cell (perform handover), as shown in step 11.

[0142] After confirming the RRC reconfiguration to the network in step 9, the UE starts to periodically report L1 beam measurements of the serving and candidate target cells, as shown in step 10.

[0143] Upon determining that there is a target candidate cell with better radio link / beam measurement than the serving cell, for example, L1 reference signal received power (RSRP) measured by the target beam > L1-RSRP measured by the serving beam + offset for a period of time (e.g., trigger time (TTT)), the serving cell sends a MAC control element (MAC CE) or L1 message in step 11 to trigger a cell change to the target candidate cell.

[0144] In step 12, the UE performs handover from the serving cell to the target cell.

[0145] The release procedure of cells prepared for the LLM procedure has not yet been agreed upon in 3GPP Rel. 18. The following relates to the RRC-based release mechanism from the CU-Control Plane (CP) based on L3 measurements.

[0146] LLM may employ the same release procedure used for L3 mobility. Figure 5 The signaling procedure for the release procedure using the L3 procedure is shown.

[0147] In step 1 and step 3, the UE provides the CU with L3 measurements of the serving cell and neighboring / target cells.

[0148] In step 3, based on the received measurements, the CU may determine to release a prepared target cell that is no longer useful for handover. For example, the CU may decide to release a target cell whose radio signal measurement value is below a threshold or much weaker than other prepared cells.

[0149] In step 4 and step 5, the UE context is released from the target DU whose control of one of the target cells is released.

[0150] In step 6, DL RRC messaging is used to transparently transmit the RRC reconfiguration message to the UE.

[0151] In steps 7 to 9, the UE is reconfigured to release the configuration of the target cell released in step 7, and forwards the confirmation back to the CU in steps 8 and 9.

[0152] Such as Figure 5 The release procedure shown requires configuration of L3 measurement reporting, although LLM is configured to the UE (in other words, L1 beam measurements of the prepared target cell are reported to the serving DU). L1 measurements and L3 measurements are performed and reported by the UE. L1 measurement reports at the DU are not used for HO decision at the CU.

[0153] Figure 5 The release process shown requires multiple F1 signaling, a total of 6 messages, namely step 2, step 4-step 7 and step 10. RRC level signaling is sent to the UE and a corresponding confirmation needs to be received from the UE. In total, there are three RRC messages (step 1, step 8 and step 9).

[0154] According to 3GPP specifications, the CU may use RRC reconfiguration to remove the prepared conditional handover (CHO) configuration of the target cell from the UE side.

[0155] This procedure is used for L3 mobility procedures and is triggered by L3 measurements. Figure 5 The signaling is the same as for the prepared target cell, and L3 measurements are also required (to be configured). Assuming that the UE will have reported the L1 beam measurements of the prepared cells to the DU, it is not clear to what extent the L3 measurements will be used to release the prepared target cell in LLM. Therefore, LLM preparation may not be performed until the UE switches to another cell. Afterwards, the UE and CU release all other prepared cells.

[0156] Failure to release LLM preparation in time may result in resources being retained in multiple DUs or cells unnecessarily. Resource reservation overhead is a challenge that has also been highlighted in conditional handover (CHO). To this end, 3GPP has defined the CHO Cancel IE to enable the release of prepared target cells that are no longer useful for handover. Similar problems will exist for LLM preparation.

[0157] Currently, UE preparation can only be released through RRC reconfiguration. This process must be controlled by the CU and may result in Figure 5 High signaling overhead shown.

[0158] It has been proposed to introduce two groups of cells for L1 / L2 based mobility, namely a pre-configured group and an active group. The pre-configured group is defined as a set of cells that are eligible and prepared for L1 / L2 mobility at the CU-CP and DU but for which L1 measurement reporting with respect to the UE is deactivated. The gNB-DU is not expected to have reserved resources for such cells. In this proposal, the CU-CP indicates to the DU (in F1: UE Context Establishment or UE Context Modification procedure) whether the cell being prepared belongs to the pre-configured group.

[0159] The active group is defined as a set of cells eligible and ready for L1 / L2 mobility at CU-CP and DU, configured by the UE for L1 RSRP reporting, with resources reserved in the gNB-DU. CSI-RS transmission is also performed. The cells in the active group are ready to take over the serving / secondary cells. The TCI state configuration includes these cells. By configuring the UE with a pre-configured group and an active group, the network ensures that the UE sends L1 measurements to the DU only for the Physical Cell Identity (PCI) of the active group.

[0160] The proposal is a proactive signaling optimization related to prepared cells. Cells are partially prepared to avoid measurement and resource reservation overhead. The proposal aims to activate only a subset of cells so that the amount of required releases will be minimized.

[0161] Conditional cell release is provided in the alternative proposal. If the condition is met, the UE uses the condition to evaluate whether to release the cell in the cell group. The UE may be instructed to indicate the release of the cell to the network. Upon such indication, a remapping or release of the bearer may occur. The condition for CPR (Conditional PSCell Release) may be one of the following: Ax measurement event, lack of data in the transmission buffer, or loss of coverage provided by the configured cell.

[0162] Figure 6 A flow chart of a method according to an example embodiment is shown.The method may be performed at a central unit (eg a central unit or a CU-CP).

[0163] In S1 , the method comprises determining a release condition for at least one cell prepared for low layer mobility of a user equipment.

[0164] In S2, the method comprises providing an indication of a release condition to a distributed unit of a serving node of the user equipment.

[0165] The release condition is the same or different for each of the multiple cells prepared for low layer mobility of the user equipment. In an example embodiment, the CU determines the release condition for each LLM prepared cell. The condition can be the same or different for all prepared target cells.

[0166] The CU configures the serving DU with release conditions for each prepared cell.

[0167] The method may include providing an indication of the release condition to the user equipment. The method may include providing a measurement configuration to the user equipment to enable evaluation of the release condition. In an example embodiment, the CU configures the UE with relevant measurements, and the serving DU then uses the relevant measurements to evaluate the release condition configured by the CU.

[0168] The release condition may include at least one of a threshold, an offset value, the number of target cells, and a target cell load. The threshold may include at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio. The release condition may be referred to as an LLM release condition.

[0169] The LLM release condition may be based on radio conditions (L1 radio conditions obtained by L1 measurements). For example, the L1 beam measurement of the prepared target cell X is below a certain value threshold Thr for a certain duration T equal to or above 0, or if the L1 beam measurement of the target cell X is below the strongest measurement of the prepared target cell by Y dB.

[0170] Parameters of the release condition (such as threshold Thr, duration T, offset Y) may be provided by the CU to the DU.

[0171] The release condition may be a RSRP / reference signal received quality (RSRQ) / L1 signal to interference and noise ratio (SINR) threshold. This may be useful in scenarios where there are a large number of network resources.

[0172] Alternatively or additionally, the LLM release condition may be based on the number of LLM prepared cells that the UE currently has. The maximum number may be, for example, 8. As a result, the release of some cells may be necessary for the addition of new cells. The LLM release condition may be based on a dynamic switching operation, where the UE switches one of its non-serving cells with a serving cell.

[0173] In scenarios where the network has sufficient resources and optimizes UE performance, the release condition can be coupled with the maximum number of prepared cells for the UE. That is, the release is triggered by the serving DU only when a new prepared cell is configured for the UE. In other words, in this scenario, as long as the maximum number of prepared cells is not reached, the release may not be triggered.

[0174] The method may include determining a release condition based on at least one of: an RSRP threshold, a service node associated with a target cell (e.g., whether the prepared cell is intra-DU or inter-DU), a total number of cells prepared for the user equipment, and a load condition of a service node associated with the target cell.

[0175] In an alternative embodiment, the release of a cell may trigger the activation of LLM preparation of another cell. This embodiment may be referred to as LLM preparation replacement.

[0176] The target cell may be associated with a distributed unit or another distributed unit. In other words, the prepared cell may be an intra-DU or inter-DU cell. Release conditions for all prepared cells are provided to the serving DU.

[0177] Figure 7 A flow chart of a method according to an example embodiment is shown.The method may be performed at a distributed unit (eg, a serving DU) of a serving node of a user equipment.

[0178] In T1 , the method includes: determining, at a distributed service node of the user equipment, that a release condition for a target cell prepared for low layer mobility of the user equipment is satisfied.

[0179] In T2, the method includes: in response to determining that the release condition is met, causing the target cell to be released.

[0180] Causing the target cell to be released may include providing an indication to a central unit (eg, CU-CP) indicating release preparation of the target cell.

[0181] In an example embodiment, the serving DU determines that a release condition holds for target cell X.

[0182] Release conditions can be found above. Figure 6 The method may include receiving, at a distributed unit of a service node, an indication of a release condition from a central unit.

[0183] In an example embodiment, the serving DU informs the CU-CP of the release of the prepared cell.The indication to the central unit may include: an identifier of the target cell or a low layer mobility preparation identifier.

[0184] The method may include: receiving at a distributed unit of a serving node at least one layer 1 measurement value from a user equipment; and determining, based on the at least one layer 1 measurement value, that a release condition for a target cell is met.

[0185] In an example embodiment, the UE reports a synchronization signal block (SSB)-resource indicator (RI)-L or a channel state information (CSI)-RI-L containing at least a CSI reference signal (RS) / SSB with a minimum RSRP value. The DU decides to release based on multiple reports received for the minimum RSRP value.

[0186] The method may include providing an indication to the user equipment to release the target cell. The indication to the user equipment may be provided in a layer 1 message (e.g., a MAC CE or a downlink control information (DCI) indication). The indication to the user equipment may include an identifier of the target cell or a low-layer mobility preparation identifier.

[0187] In an example embodiment, when the release condition is met, the serving DU sends a MAC CE message to release the LLM prepared cell X at the UE, ie, releases the LLM configuration of the prepared target cell X.

[0188] The indication to the user equipment may include an indication of whether layer 1 measurements for the target cell should be continued. For example, a MAC CE message indicating release of the prepared cell configuration may also include whether the UE should continue reporting configuration including CSI resources for the target cell or not as an additional parameter.

[0189] The method may include providing a measurement configuration to the user equipment. For example, the DU may configure the CSI measurement reporting event to report at least the RSRP value of the CSI-RS resource group, or to report the SSB-RI or CSI-RS resource indicator (CRI) of the resources that meet the discard condition. The details of the autonomous release condition configured to the UE are related to other LLM preparations, because the number of LLM preparations and / or the configuration of the filtering used at the DU, the parameters of the L1 filtering used for LLM at the DU may be indicated, so that the UE can decide when the preparation can be released.

[0190] Figure 8 A signaling diagram between the UE, serving DU, target DU and CU-CP is shown.

[0191] In step 1, the UE sends L3 measurements of the serving and neighboring target cells to the DU. The serving DU transparently forwards the L3 measurements to the CU. The CU establishes a UE context at the target DU controlling the target cell and receives a response.

[0192] In step 2, the CU-CP compiles the RRC reconfiguration for the target cell as part of the LLM and sends the message to the serving DU. The CU indicates the LLM preparation ID to the DU.

[0193] Step 3 and step 4 can be combined with this step for efficient signaling.

[0194] In step 3, the UE receives LLM preparation with measurement configuration that enables evaluation of release conditions at the serving DU. The LLM preparation for each cell has a separate LLM preparation ID.

[0195] In step 4, the UE confirms the new configuration and the DU forwards the message to the CU.

[0196] In step 5: the CU-CP determines the LLM release condition.

[0197] In step 6: CU-CP sends a UE context modification message to the serving DU, notifying the DU of the UE context change and attaching release conditions.

[0198] In step 7: The DU starts monitoring the release condition. The serving DU uses the L1 beam measurements received from the UE in step 10 to evaluate the release condition.

[0199] In an alternative embodiment, without providing the DU with a radio threshold, for example, the DU may decide to release the LLM preparation in step 11 based on its own assessment of the radio conditions.

[0200] In step 9 to step 10, the L1 measurement at the UE meets the criteria to be reported, and the UE sends a report to the serving DU.

[0201] In step 11, the source DU determines to release the LLM preparation of the target cell X as a result of the release condition evaluation using the reported L1 beam measurement.

[0202] In step 12: the source DU sends a MAC CE message to indicate the LLM preparation IDs that need to be released. The source DU can indicate a list of LLM preparation IDs to the UE.

[0203] Alternatively, the serving DU may indicate the ID of the target cell to be released. In one alternative, the message may be skipped (ie, no MAC CE msg is sent).

[0204] In step 13, the source DU indicates to the CU the list of LLM preparation IDs released from the UE side. Alternatively, the serving DU indicates to the CU the ID of the target cell to be released.

[0205] In an alternative, the source DU indicates this message without sending a message to the UE in step 12. This indicates that the source DU will not trigger LLM for this cell. The CU may proceed to release the target cell.

[0206] In steps 14 and 15, the CU notifies the target DU of the release of the LLM preparation. The target DU releases the resources reserved for the LLM preparation. For intra-DU mobility scenarios, steps 14 and 15 may not be required.

[0207] In scenarios involving the introduction of two groups of cells (pre-configured group and active group) for L1 / L2 based mobility, if the network prefers to keep the prepared cell configuration of the UE (without reserving resources in the corresponding DU), the prepared cell release can be modified to include two steps.

[0208] First, the prepared cells are moved from the "active set" to the "pre-configured set". This triggers the release of reserved resources on the network side, but the prepared cell configuration is maintained at both the UE and the network.

[0209] Second, the prepared cell configuration is released from the "pre-configured group". This triggers the release of the reserved resources and the prepared cell configuration at both the UE and the network.

[0210] This may require defining two separate release conditions for Figure 8 Modification of step 3 to step 4 in the MSC. In addition, as a Figure 8 The modification of step 11 to step 12 in the MSC of the serving DU comprises two separate release operations of i) releasing the cell from the pre-configured group and ii) moving the cell from the active group back to the pre-configured group.

[0211] As reference Figures 6 to 8 The described method may remove at least one F1 round trip time (RTT) delay between the CU and DU (10ms to 20ms reduction, assuming 5ms to 10ms one-way delay between the CU and DU) when releasing the configured target cell at the UE.

[0212] This idea can be used for high RTT scenarios with very long F1 links, such as high altitude platform (HAPS) or non-terrestrial network (NTN) scenarios. There can be faster adjustments to signal conditions towards the UE, which may be useful for higher frequencies where conditions can change very quickly.

[0213] An apparatus may include means for: determining, at a distributed unit of a serving node of a user equipment, that a release condition for a target cell prepared for low layer mobility of the user equipment is satisfied; and causing the target cell to be released in response to determining that the release condition is satisfied.

[0214] An apparatus may include means for determining a release condition for at least one cell prepared for low layer mobility of a user equipment; and providing an indication of the release condition to a distributed unit of a serving node of the user equipment.

[0215] Alternatively, an apparatus may include means for receiving, at a distributed unit of a serving node of the user equipment from a central unit, an indication of a release condition for at least one cell prepared for low layer mobility of the user equipment.

[0216] It should be understood that the apparatus may include or be coupled to other units or modules, such as a radio component or radio head, for use in or for transmitting and / or receiving. Although the apparatus has been described as one entity, different modules and memories may be implemented in one or more physical or logical entities.

[0217] Note that while some embodiments have been described with respect to 5G networks, similar principles may be applied with respect to other networks and communication systems. Thus, while certain embodiments are described above by way of example with reference to certain example architectures for wireless networks, technologies, and standards, the embodiments may be applied to any other suitable form of communication system in addition to the communication system shown and described herein.

[0218] It is also noted herein that while the above describes exemplifying embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the present invention.

[0219] As used herein, “at least one of: ” and “at least one of ” and similar expressions, where a list of two or more elements is combined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0220] In general, various embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device, but the disclosure is not limited thereto. Although various aspects of the disclosure may be shown and described as block diagrams, flow charts, or using some other graphical representation, it is well understood that the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general purpose hardware or controllers or other computing devices, or some combination thereof as non-limiting examples.

[0221] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware circuit implementation only (such as implementation only in analog and / or digital circuits) and (b) a combination of hardware circuitry and software such as (where applicable): (i) a combination of analog and / or digital hardware circuits and software / firmware; and (ii) any portion of a hardware processor with software (including a digital signal processor, software and memory that work together to enable a device such as a mobile phone or server to perform various functions); and (c) A hardware circuit and / or processor, such as a microprocessor or portion of a microprocessor, that requires software (e.g., firmware) for operation, but in which the software may not be present when not required for operation.

[0222] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example and if applicable to the particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0223] Embodiments of the present disclosure may be implemented by computer software executable by a data processor of a mobile device, such as in a processor entity, or by hardware, or by a combination of software and hardware. Computer software or programs (also referred to as program products, including software routines, applets and / or macros) may be stored in any device-readable data storage medium, and they include program instructions for performing specific tasks. A computer program product may include one or more computer executable components that are configured to perform an embodiment when the program is running. One or more computer executable components may be at least one software code or part thereof.

[0224] In addition, in this regard, it should be noted that any box of the logic flow as in the accompanying drawings can represent a program step, or an interconnected logic circuit, box and function, or a combination of a program step and a logic circuit, a box and a function. Software can be stored on a physical medium such as a memory chip or a memory block implemented in a processor, a magnetic medium such as a hard disk or a floppy disk, and an optical medium such as a DVD and its data variant CD. Physical media is a non-transient medium. As used herein, the term "non-transient" is a limitation of the medium itself (i.e., tangible, rather than a signal), rather than a limitation of data storage persistence (e.g., RAM to ROM).

[0225] The memory may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. As non-limiting examples, the data processor may be of any type suitable for the local technical environment and may include one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), an FPGA, a gate-level circuit, and a processor based on a multi-core processor architecture.

[0226] Embodiments of the present disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is a highly automated process. Complex and powerful software tools are available to convert logic level designs into semiconductor circuit designs that are ready to be etched and formed on semiconductor substrates.

[0227] The scope of protection sought by various embodiments of the present disclosure is set out by the independent claims. Embodiments and features described in this specification that do not fall within the scope of the independent claims, if any, should be interpreted as examples that help understand the various embodiments of the present disclosure.

[0228] The foregoing description has provided a complete and informative description of exemplary embodiments of the present disclosure by way of non-limiting examples. However, when read in conjunction with the accompanying drawings and the appended claims, various modifications and adaptations may become apparent to those skilled in the relevant art in view of the foregoing description. However, all such and similar modifications of the teachings of the present disclosure will still fall within the scope of the present invention as defined in the appended claims. In fact, there is another embodiment comprising a combination of one or more embodiments with any other embodiment previously discussed.

Claims

1. A device comprising components for: At a distributed unit of a serving node of a user equipment, determining that a release condition for a target cell prepared for low layer mobility of the user equipment is satisfied; and In response to determining that the release condition is satisfied, causing the target cell to be released.

2. The apparatus according to claim 1, wherein the component for causing the target cell to be released comprises: Means for providing an indication to a central unit indicating release preparation of said target cell.

3. The apparatus of claim 2, wherein the indication to the central unit comprises: The identifier of the target cell or a low-layer mobility preparation identifier.

4. The device according to any one of claims 1 to 3, comprising means for: receiving at least one layer 1 measurement value from the user equipment at the distributed unit of the serving node; and Based on the at least one layer 1 measurement value, it is determined that the release condition for the target cell is met.

5. The apparatus according to any one of claims 1 to 4, wherein the means for causing the target cell to be released comprises means for providing an indication to the user equipment to release the configuration of the target cell. The apparatus of claim 5 , wherein the indication to the user equipment is provided in a layer 1 message. 7 . The apparatus of claim 6 , wherein the layer 1 message comprises a medium access control element (MAC CE) or a downlink control information (DCI) indication.

8. The apparatus according to any one of claims 5 to 7, wherein the indication to the user equipment comprises an indication of whether layer 1 measurements for the target cell should be continued.

9. The apparatus according to any one of claims 5 to 8, wherein the indication to the user equipment comprises an identifier of the target cell or a low layer mobility preparation identifier.

10. The apparatus according to any one of claims 1 to 9, wherein the release condition comprises at least one of a threshold, an offset value, the number of target cells, and a target cell load. 11 . The apparatus according to claim 10 , wherein the threshold comprises at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

12. An apparatus according to any of claims 1 to 11, comprising means for receiving an indication of the release condition at the distributed unit of the serving node from a central unit.

13. A method comprising: determining, at a distributed unit of a serving node of a user equipment, that a release condition for a target cell prepared for low layer mobility of the user equipment is satisfied; as well as In response to determining that the release condition is satisfied, causing the target cell to be released.

14. An apparatus comprising: at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: determining, at a distributed unit of a serving node of a user equipment, that a release condition for a target cell prepared for low layer mobility of the user equipment is satisfied; as well as In response to determining that the release condition is satisfied, causing the target cell to be released.

15. A computer-readable medium comprising instructions that, when executed by a device, cause the device to at least: At a distributed unit of a serving node of a user equipment, determining that a release condition for a target cell prepared for low layer mobility of the user equipment is satisfied; and In response to determining that the release condition is satisfied, causing the target cell to be released.

16. An apparatus comprising components for: determining a release condition for at least one cell prepared for low layer mobility of a user equipment; and An indication of the release condition is provided to a distributed unit of a serving node of the user equipment.

17. The apparatus according to claim 16, wherein the release condition comprises at least one of a threshold, an offset value, the number of target cells, and a target cell load.

18. The apparatus according to claim 17, wherein the threshold comprises at least one of a reference signal received power, a reference signal received quality, and a layer 1 signal to interference and noise ratio.

19. An apparatus according to any of claims 16 to 18, comprising means for providing a measurement configuration to the user equipment to enable evaluation of the release condition.

20. An apparatus as claimed in any one of claims 16 to 19, comprising means for providing an indication of the release condition to the user equipment.

21. The apparatus according to any one of claims 16 to 20, comprising a component for determining the release condition based on at least one of the following: a reference signal received power threshold, the service node associated with the target cell, the total number of cells prepared for the user equipment, and a load condition of the service node associated with the target cell.

22. The apparatus according to any one of claims 16 to 21, wherein the release condition is the same or different for each cell of a plurality of cells prepared for low layer mobility of the user equipment.

23. An apparatus according to any one of claims 16 to 22, wherein the target cell is associated with the distributed unit or a further distributed unit.

24. An apparatus comprising components for: An indication of a release condition for at least one cell prepared for low layer mobility of the user equipment is received from a central unit at a distributed unit of a serving node of the user equipment.

25. A method comprising: determining a release condition for at least one cell prepared for low layer mobility of a user equipment; as well as An indication of the release condition is provided to a distributed unit of a serving node of the user equipment.

26. A method comprising: An indication of a release condition for at least one cell prepared for low layer mobility of the user equipment is received from a central unit at a distributed unit of a serving node of the user equipment.

27. An apparatus comprising: at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: determining a release condition for at least one cell prepared for low layer mobility of a user equipment; as well as An indication of the release condition is provided to a distributed unit of a serving node of the user equipment.

28. An apparatus comprising: at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: An indication of a release condition for at least one cell prepared for low layer mobility of the user equipment is received from a central unit at a distributed unit of a serving node of the user equipment.

29. A computer-readable medium comprising instructions that, when executed by a device, cause the device to at least: determining a release condition for at least one cell prepared for low layer mobility of a user equipment; and An indication of the release condition is provided to a distributed unit of a serving node of the user equipment.

30. A computer-readable medium comprising instructions that, when executed by an apparatus, cause the apparatus to at least: An indication of a release condition for at least one cell prepared for low layer mobility of the user equipment is received from a central unit at a distributed unit of a serving node of the user equipment.

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