Conditional lower layer triggered mobility

Abstract

There is provided 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 at least to: establish a connection via a source cell provided by a radio access network; receive, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition; measure a signal quality of at least one beam of at least one target candidate cell; determine to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell; receive, via the source cell, a medium access control element, MAC CE, message, said MAC CE message comprising information related to the measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the apparatus; and monitor the execution condition, and in response to determining that the execution condition is fulfilled, select a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

Description

[0001] APPARATUS, METHODS, AND COMPUTER PROGRAMS RELATING TO CONDITIONAL LOWER LAYER TRIGGERED MOBILITY

[0002] TECHNICAL FIELD

[0003] Various example embodiments of this disclosure relate to methods, apparatus, and computer programs and in particular but not exclusively relating to apparatus, methods, and computer programs relating to conditional lower layer triggered mobility, LTM.

[0004] BACKGROUND

[0005] A communication network can be seen as a facility that enables communications between two or more communication devices or provides communication devices access to a data network. A mobile or wireless communication network is one example of a communication network. A communication device may be provided with a service by an application server.

[0006] Such communication networks operate in according with standards such as those provided by 3GPP (Third Generation Partnership Project) or ETSI (European Telecommunications Standards Institute). Examples of standards are the so-called 5G (5th Generation) standards and 6G (6th Generation) standards provided by 3GPP.

[0007] BRIEF DESCRIPTION

[0008] Some example embodiments of this disclosure will be described with respect to certain aspects. These aspects are not intended to indicate key or essential features of the embodiments of this disclosure, nor are they intended to be used to limit the scope of thereof. Other features, aspects, and elements will be readily apparent to a person skilled in the art in view of this disclosure.

[0009] According to a first aspect, there is provided 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 at least to: establish a connection via a source cell provided by a radio access network; receive, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition; measure a signal quality of at least one beam of at least one target candidate cell; determine to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell tothe target candidate cell; receive, via the source cell, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to the measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the apparatus; and monitor the execution condition, and in response to determining that the execution condition is fulfilled, select a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0010] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam being one of the at least one potential neighbour beam, selecting that best beam as the beam for handover.

[0011] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam not being one of the at least one potential neighbour beam, determining if one or more of the at least one potential neighbour beam satisfy the execution condition.

[0012] When it is determined that one or more of the at least one potential neighbour beam satisfy the execution condition, selecting a beam for handover may comprise selecting one of the at least one potential neighbour beam satisfying the execution condition as the beam for handover.

[0013] When it is determined that no one of the at least one potential neighbour beam satisfy the execution condition, the instructions, when executed by the at least one processor, may further cause the apparatus to perform a random-access procedure.

[0014] The MAC CE message may further comprise timing advance information for the target candidate cell.

[0015] The instructions, when executed by the at least one processor, may further cause the apparatus to receive a further MAC CE message, said further MAC CE message comprising timing advance information for the target candidate cell.

[0016] The information related to the measured beam of the target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.The apparatus may be provided in or be a user equipment.

[0017] According to a second aspect, there is provided a method comprising: establishing a connection via a source cell provided by a radio access network; receiving, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition; measuring a signal quality of at least one beam of at least one target candidate cell; determining to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell; receiving, via the source cell, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to the measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the apparatus; and monitoring the execution condition, and in response to determining that the execution condition is fulfilled, selecting a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0018] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam being one of the at least one potential neighbour beam, selecting that best beam as the beam for handover.

[0019] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam not being one of the at least one potential neighbour beam, determining if one or more of the at least one potential neighbour beam satisfy the execution condition.

[0020] When it is determined that one or more of the at least one potential neighbour beam satisfy the execution condition, selecting a beam for handover may comprise selecting one of the at least one potential neighbour beam satisfying the execution condition as the beam for handover.

[0021] When it is determined that no one of the at least one potential neighbour beam satisfy the execution condition, the method may comprise performing a random-access procedure.

[0022] The MAC CE message may further comprise timing advance information for the target candidate cell.The method may comprise receiving a further MAC CE message, said further MAC CE message comprising timing advance information for the target candidate cell.

[0023] The information related to the measured beam of the target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.

[0024] The method may be performed by an apparatus.

[0025] The apparatus may be provided in or be a user equipment.

[0026] The apparatus may comprise one or more means for performing the methods discussed in relation to the second aspect.

[0027] According to a third aspect, there is provided an apparatus comprising: means for establishing a connection via a source cell provided by a radio access network; means for receiving, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition; means for measuring a signal quality of at least one beam of at least one target candidate cell; means for determining to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell; means for receiving, via the source cell, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to the measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the apparatus; means for monitoring the execution condition; and means for selecting, in response to determining that the execution condition is fulfilled, a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0028] The apparatus may be provided in or be a user equipment.

[0029] According to a fourth aspect, there is provide 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 at least to: establish a connection with a user equipment; transmit to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition; receive a measurement report from the user equipment comprising a signal quality of atleast one beam of at least one target candidate cell; make an early timing advance decision; send to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure; and transmit to the user equipment, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to a measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the user equipment.

[0030] The MAC CE message may further comprise timing advance information for the target candidate cell.

[0031] The instructions, when executed by the at least one processor, may further cause the apparatus to transmit a further MAC CE message, said further MAC CE message comprising timing advance information for the target candidate cell.

[0032] The information related to the measured beam of the target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.

[0033] The apparatus may be or provided in a network node. The network node may be an access node. The apparatus may be or provided in a distributed unit of a base station.

[0034] According to a fifth aspect, there is provided a method comprising: establishing a connection with a user equipment; transmitting to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition; receiving a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell; making an early timing advance decision; sending to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure; and transmitting to the user equipment, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to a measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the user equipment.

[0035] The MAC CE message may further comprise timing advance information for the target candidate cell.The method may comprise transmitting a further MAC CE message, said further MAC CE message comprising timing advance information for the target candidate cell.

[0036] The information related to the measured beam of the target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.

[0037] The apparatus may be or provided in a network node. The network node may be an access node. The apparatus may be or provided in a distributed unit of a base station.

[0038] The method may be performed by an apparatus.

[0039] The apparatus may be or provided in a network node. The network node may be an access node. The apparatus may be or provided in a distributed unit of a base station.

[0040] The apparatus may comprise one or more means for performing the methods discussed in relation to the fifth aspect.

[0041] According to a sixth aspect, there is provided an apparatus comprising: means for establishing a connection with a user equipment; means for transmitting to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition; receiving a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell; means for making an early timing advance decision; means for sending to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure; and means for transmitting to the user equipment, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to a measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the user equipment.

[0042] According to a seventh aspect, there is provided 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 at least to: establish a connection via a source cell provided by a radio access network; receive, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information relatedto at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell; measure a signal quality of at least one beam of at least one target candidate cell; determine to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell; and monitor the execution condition, and in response to determining that the execution condition is fulfilled, select a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0043] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam being one of the at least one potential neighbour beam, selecting that best beam as the beam for handover.

[0044] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam not being one of the at least one potential neighbour beam, determining if one or more of the at least one potential neighbour beam satisfy the execution condition.

[0045] When it is determined that one or more of the at least one potential neighbour beam satisfy the execution condition, one of the at least one potential neighbour beam satisfying the execution condition may be selected as the beam for handover.

[0046] When it is determined that no one of the at least one potential neighbour beam satisfy the execution condition, the instructions, when executed by the at least one processor, may further cause the apparatus to perform a random-access procedure.

[0047] The instructions, when executed by the at least one processor, may further cause the apparatus to receive a medium access control control element, MAC CE, message, said further MAC CE message comprising timing advance information for the target candidate cell.

[0048] The instructions, when executed by the at least one processor, may further cause the apparatus to receive a preamble for the early timing advance request.

[0049] The information related to the beam of the potential target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.The configuration related to conditional LTM may be received in a radio resource control message.

[0050] The apparatus is or may be comprised in a user equipment.

[0051] According to an eight aspect, there is provided a method comprising: establishing a connection via a source cell provided by a radio access network; receiving, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information related to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell; measuring a signal quality of at least one beam of at least one target candidate cell; determining to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell; monitoring the execution condition; and in response to determining that the execution condition is fulfilled, selecting a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0052] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam being one of the at least one potential neighbour beam, selecting that best beam as the beam for handover.

[0053] Selecting a beam for handover may comprise determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam not being one of the at least one potential neighbour beam, determining if one or more of the at least one potential neighbour beam satisfy the execution condition.

[0054] When it is determined that one or more of the at least one potential neighbour beam satisfy the execution condition, one of the at least one potential neighbour beam satisfying the execution condition may be selected as the beam for handover.

[0055] When it is determined that no one of the at least one potential neighbour beam satisfy the execution condition, the method may comprise performing a random-access procedure.

[0056] The method may comprise receiving a medium access control control element, MAC CE, message, said MAC CE message comprising timing advance information for the targetcandidate cell.

[0057] The method may comprise receiving a preamble for the early timing advance request.

[0058] The information related to the beam of the potential target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.

[0059] The method may be performed by an apparatus.

[0060] The apparatus may be provided in or be a user equipment.

[0061] The apparatus may comprise one or more means for performing the methods discussed in relation to the eighth aspect.

[0062] According to a ninth aspect, there is provided an apparatus comprising: means for establishing a connection via a source cell provided by a radio access network; means for receiving, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information related to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell; means for measuring a signal quality of at least one beam of at least one target candidate cell; means for determining to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell; means for monitoring the execution condition; and means for, in response to determining that the execution condition is fulfilled, selecting a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0063] According to a tenth aspect, there is provided 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 at least to: establish a connection with a user equipment; transmit to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information related to at least one potentialneighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell; receive a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell; make an early timing advance decision; and send to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure.

[0064] The method may comprise transmitting a medium access control control element, MAC CE, message, said MAC CE message comprising timing advance information for the target candidate cell.

[0065] The information related to the beam of the potential target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.

[0066] The configuration related to conditional LTM may be provided to the user equipment in a radio resource control message.

[0067] The apparatus may be or provided in a network node. The network node may be an access node. The apparatus may be or provided in a distributed unit of a base station.

[0068] According to a eleventh aspect, there is provided a method comprising: establishing a connection with a user equipment; transmitting to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information related to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell; receiving a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell; making an early timing advance decision; and sending to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure.

[0069] The method may comprise transmit a medium access control control element, MAC CE, message to the user equipment, said MAC CE message comprising timing advance information for the target candidate cell.

[0070] The information related to the beam of the potential target candidate cell and to the at least one potential neighbour beam may comprise one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB,identity.

[0071] The configuration related to conditional LTM may be provided to the user equipment in a radio resource control message.

[0072] The method may be performed by an apparatus, The apparatus may be or provided in a network node. The network node may be an access node. The apparatus may be or provided in a distributed unit of a base station.

[0073] The apparatus may comprise one or more means for performing the methods discussed in relation to the eleventh aspect.

[0074] According to a twelfth aspect, there is provided an apparatus comprising: means for establishing a connection with a user equipment; means for transmitting to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information related to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell; means for receiving a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell; means for making an early timing advance decision; and means for sending to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure.

[0075] According to another aspect, there is provided a computer readable medium comprising program instructions stored thereon for performing at least one of the above methods.

[0076] According to an aspect, there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least one of the above methods.

[0077] According to an aspect, there is provided a non-volatile tangible memory medium comprising program instructions stored thereon for performing at least one of the above methods.

[0078] In the above, many different aspects have been described. It should be appreciated that further aspects may be provided by the combination of any two or more of the aspects described above.

[0079] Various other aspects are also described in the following detailed description and in the attached claims.LIST OF THE DRAWINGS

[0080] In the following, the invention will be described in greater detail with reference to the embodiments and the accompanying drawings, in which

[0081] Fig. 1 shows an example of a communication network to which examples disclosed herein may be applied;

[0082] Fig. 2 shows a signalling diagram illustrating an example of lower layer triggered mobility;

[0083] Fig.3 shows an example of channel status information reference signal CSI- RS beam quasi co located QCL with synchronization signal block SSB beam;

[0084] Fig.4 shows a first example of a signaling flow diagram;

[0085] Fig. 5 shows a second example of a signaling flow diagram;

[0086] Fig. 6 shows a third example of a signaling flow diagram;

[0087] Fig. 7 shows, a first example of a method;

[0088] Fig. 8 shows, a second example of a method;

[0089] Fig.9 shows, a third example of a method;

[0090] Fig. 10 shows, a fourth example of a method;

[0091] Fig. 11 shows an example of an apparatus.

[0092] DESCRIPTION OF EMBODIMENTS

[0093] The following embodiments are exemplary. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Further, when a particular feature, structure, or characteristic is described in connection of an embodiment, it is within the knowledge of one skilled in the art to apply such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that although the terms “first,” “second” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0094] For the purposes of the present disclosure, the phrases “at least one of A or B”, “at least one of A and B”, and “A and / or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and / or C” means (A), (B), (C), (A and B), (A andC), (B and C), or (A, B, and C).

[0095] Embodiments described may be implemented in a communication network, such as any of the following radio access technologies (RATs): Worldwide Interoperability for Micro-wave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, and enhanced LTE (eLTE), 5G (also called NR), or any future RAT such as 6G. Moreover, communication within the communication network may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (M1M0), Orthogonal Frequency Division Multiple (OFDM), and / or Discrete Fourier Transform spread OFDM (DFT-s-OFDM).

[0096] As used herein, the term “network device” or “network node” refers to a node in a communication network via which user equipment may access the network and / or which is capable of controlling radio communication and managing radio resources within a cell. The network node or network device may be referred to as a base station (BS), an access point (AP) or an access node. The network device may be, depending on the applied technology, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (1AB) node, a low power node, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, or an aircraft network device.

[0097] Moreover, in connection of split radio access network (RAN), the network device may refer to a centralised unit (CU) of a base station and / or a distributed unit (DU) of a base station. An interface between CU and DU may be referred to as an Fl interface in NR. In the split RAN architecture, node operations may be carried out, at least partly, in the central / centralized unit, CU, (e.g. server, host or node) operationally coupled to the DU, (e.g. a radio head / node). One CU may control one or more DUs, acting at least as trans-mit / receive (Tx / Rx) nodes. In some embodiments, the DUs may comprise e.g. a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereasthe CU may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layers. Other functional splits are possible too. In practice, any processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may depend on the applied implementation.

[0098] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example, a terminal device may be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), or a Mobile Station (MS). The terminal device may include a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, USB dongles, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like.

[0099] A term “resource”, as used herein, may refer to radio resources in time domain, in frequency domain, in space domain, and / or in code domain. Some examples of resources include e.g. a physical resource block (PRB), a radio frame, a subframe, a time slot, a subband, a frequency region, a sub-carrier, a beam, etc. The term “transmission” and / or “reception” may refer to wirelessly transmitting and / or receiving via a wireless propagation channel on radio resources.

[0100] Fig. 1 illustrates an example of a communication network to which examples disclosed herein may be applied. The communication network or a cellular communication network may comprise a network node 110 providing one or more cells, such as cell 100, and a network node 112 providing one or more other cells, such as cell 102. Each cell may be, e.g., a macro cell, a micro cell, femto, or a pico cell, for example. The cell may define a coverage area or a service area of the corresponding access node.

[0101] The network node 110 may provide a user equipment (UE) 120 (one or more UEs) with wireless access to the communication network. The wireless access may comprise downlink (DL) communication from the network node to the UE 120 and uplink (UL)communication from the UE 120 to the network node. Examples of uplink channels comprise physical uplink control channel (PUCCH) for transmitting control information and physical uplink shared channel (PUSCH) for transmitting data towards the network. Examples of downlink channels comprise physical downlink control channel (PDCCH) for transmitting control information and physical downlink shared channel (PDSCH) for transmitting data towards the user equipment.

[0102] There may be a plurality of UEs 120, 122 in the system. Each of them may be served by the same or by different network nodes 110, 112. UE may be configured with dual connectivity (DC), wherein the UE, e.g. UE 120, may be connected to multiple network nodes 110, 112. The UEs 120, 122 may communicate with each other, in case device-to-device (D2D) communication interface is established between them via a so-called sidelink (SL). Such D2D communications may be referred to as machine-to-machine, peer-to-peer (P2P) communications, or vehicle-to-vehicle (V2V), for example.

[0103] In the case of multiple network nodes in the communication network, the network nodes may be connected to each other via an interface. LTE specifications call such an interface as X2 interface. An interface between an LTE node and a 5G node, or between two 5G nodes may be called Xn interface.

[0104] The network nodes 110 and 112 may be further connected via another interface to a core network 116 of the communication network. The LTE specifications specify the core network as an evolved packet core (EPC), and the core network may comprise e.g. a mobility management entity (MME) and a gateway node. The MME may handle mobility of terminal devices in a tracking area encompassing a plurality of cells and handle signalling connections between the terminal devices and the core network. The gateway node may handle data routing in the core network and to / from the terminal devices. The 5G specifications specify the core network as a 5G core (5GC). The 5G core may comprise e.g. an access and mobility management function (AMF) and a user plane function / gateway (UPF) and other functions. The AMF may handle termination of non-access stratum (NAS) signalling, NAS ciphering & integrity protection, registration management, connection management, mobility management, access authentication and authorization, security context management. The UPF node may support packet routing and forwarding, packet inspection and quality of service (QoS) handling, for example.

[0105] In 3GPP Rel-18, a new mobility mechanism was introduced, namely lower layer-triggered mobility (LTM), which aims to reduce interruption time during handover.The overall procedure for LTM is illustrated in the signalling diagram in Fig.2, with reference to the network components schematically illustrated in Fig.l. Fig.2 is taken from Fig.9.2.3.5.2-1 of TS38.300vl8. As described in TS38.300vl8, 9.2.3.5.2, the procedure for LTM is as follows:

[0106] In Step 1 of Fig.2 the UE, for example the UE 120 sends a Measurement Report message to the gNB 110, which provides access to the source cell 100. The gNB 110 decides to configure LTM and initiates LTM preparation.

[0107] In Step 2 of Fig.2, the gNB 110 transmits an RRC Reconfiguration message to the UE 120 including the LTM candidate configurations.

[0108] In Step 3 of Fig.2 the UE 120 stores the LTM candidate configurations and transmits an RRC Reconfiguration Complete message to the gNB 110.

[0109] In Step 4a of Fig.2, the UE 120 performs DL synchronization with the candidate cell(s) 102 before receiving the cell switch command.

[0110] In Step 4b of Fig.2, when the UE-based TA measurement is configured, the UE 120 acquires the TA value(s) of the candidate cell(s) 102 by measurement. The UE 120 performs early TA acquisition with the candidate cell(s) 102 as requested by the network before receiving the cell switch command as specified in clause 9.2.6. This is done via contention free random access, CFRA triggered by a PDCCH order from the source cell 100, following which the UE 120 sends preamble towards the indicated candidate cell 102. In order to minimize the data interruption of the source cell 100 due to CFRA towards the candidate cell(s) 102, the UE 120 does not receive a random-access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell 102 is instead indicated in the cell switch command. The UE 120 does not maintain the TA timer for the candidate cell 102 and relies on network implementation to guarantee the TA validity.

[0111] In Step 5 of Fig. 2 the UE 120 performs LI measurements on the configured candidate cell(s) 102 and transmits LI measurement reports to the source gNB 110. LI measurement should be performed as long as the RRC re-configuration (from step 2) is applicable.

[0112] In Step 6 of Fig. 2, the gNB 110 decides to execute a cell switch from the source cell 100 to the candidate or target cell 102 and transmits a MAC CE triggering cell switch by including the candidate configuration index of the target cell 102. The UE 120 thenswitches to the target cell 102 and applies the configuration indicated by candidate configuration index.

[0113] In Step 7 of Fig. 2 the UE 120 performs the random-access procedure towards the target cell 102, if the UE 120 does not have a valid TA of the target cell 102,

[0114] In Step 8 of Fig. 2, the UE 120 completes the LTM cell switch procedure by sending RRC Reconfiguration Complete message to the gNB 112 providing access to the target cell 102.

[0115] If the UE 120 has performed a RA procedure in Step 7 of Fig. 2 then the UE 120 considers that LTM cell switch execution is successfully completed when the random access procedure is successfully completed.

[0116] For RACH-less LTM, the UE 120 considers that the LTM cell switch execution is successfully completed when the UE 120 determines that the network has successfully received its first UL data.

[0117] As seen above, in LTM, early TA acquisition, i.e. TA acquisition before handover / cell switch, can be performed in the following ways:

[0118] Firstly, the network can order the UE 120 to perform random access (RA) preamble transmission to a candidate cell 102. The candidate cell 102 uses the received RA preamble to estimate the TA and provides the TA estimate to the source cell 100. When the source cell 100 decides to trigger the cell switch, it provides the estimated TA value along with the cell switch command.

[0119] Secondly, during LTM preparation, the network can configure the UE 120 to perform UE-based TA measurements. UE-based TA measurements may be performed based on the TA of the serving cell 100 and the measured time difference between the candidate cell 102 and the serving cell 100. After being configured, the UE 120 is assumed to obtain a TA measurement before a cell switch command is issued by the gNB 110 providing access to the source cell 100.

[0120] Another purpose served by random access is that the target gNB 112 is notified about the presence of the UE 120 and resources for the UE’s subsequent transmissions are provided to the UE 120. Hence, when RACH-less LTM cell switch is performed, a mechanism is required to support the initial transmission of the UE 120 to the target cell 102. A mechanism that supports this purpose is the provisioning of configured grants, which consist of sets of resources in the candidate / target cell that the UE 120 may use if / when it performs its initial transmission after handover / cell switch to the target cell102. An alternative to this mechanism is to provide an access notification from the source cell 100 to the target cell 102, so that the target cell 102 can then provide a dynamic grant to the UE 120 for the target cell 102.

[0121] Rel-18 LTM supports early DL synchronization through early TCI state activation for one or more candidate cells before the cell switch command. The network sends a candidate cell specific MAC-CE to activate one or more TCI states for a candidate cell. If the network wants to activate TCI states for more than one candidate cell, the network sends a separate MAC-CE for each of those cells. At the time of receiving the TCI state activation MAC-CE, the UE performs DL synchronization with the SSB(s) or tracking reference signals TRS associated to the target TCI state(s).

[0122] When TCI state is considered active and the UE has DL synchronization of the target TCI state, cell switch delay does not comprise time for DL synchronization. When TCI state is not on the active TCI state list or when the UE does not have DL synchronization of the target TCI state, the UE is allowed time to perform DL synchronization during the cell switch.

[0123] L3 conditional handover is where the network configures the UE with one or more signal threshold-based conditions for one or more cells. The UE evaluates the conditions and in the event of a condition for a cell becoming met, executes conditional handover without a handover command to this cell.

[0124] Some embodiments may relate to conditional LTM, CLTM.

[0125] Some embodiments may relate to a lower layer-triggered mobility (LTM). LTM aims to reduce the interruption time during handover.

[0126] For event-triggered LI LTM measurement reporting, max N may be the total number of all beams included into a (measurement report) MR MAC CE.

[0127] For event-triggered LI LTM measurement reporting, the network may control if the beam(s) not satisfying the event could be reported according to N beams in the MR MAC CE.

[0128] TCI (transmission configuration indicator) state may associate one or two DL reference signals with a corresponding quasi-colocation (QCL) type.

[0129] For conditional intra-CU LTM, the candidate cell TCI states activation / deactivation MAC CE may be re-used for the early activation / deactivation of TCI state(s) of a CLTM candidate configuration.For conditional intra-CU LTM, the network may inform the TA information of the candidate cell to the UE via a MAC CE, which is the TA value when the UE switches to that candidate cell during CLTM.

[0130] Some embodiments may address the issue that for CLTM configured candidate cells, when the early TA procedure is completed, for RACH-less C-LTM the UE needs to trigger an uplink message towards the same SSB for which Early TA was completed.

[0131] Some embodiments may address the issue that TCI state activation may only activate a subset of beams.

[0132] Some embodiments may address the issue that if the UE executes the C-LTM at a later point in time, the UE may find other beams as a strong beam.

[0133] In some embodiments, the UE is able to consider additional beams for RACH-less handover from the serving cell.

[0134] In some embodiments, a MAC-CE command providing the TA value may further provide additional information on other potential beams where the UE can continue the RACH-less C-LTM

[0135] In some embodiments, a MAC-CE command providing for early TCI state may provide additional beams UE can consider continuing with RACH-less LTM for a DG (dynamic grant) based option.

[0136] In some embodiments, RRC configuration may provide allowed or potential neighbour SSB beams for each SSB beam. For a SSB#2 beam triggered condition, it is possible to do RACH-less handover also with SSB#1 and SSB#3 where SSB#1 and SSB#3 are potential neighbour beams to SSB#2.

[0137] To reduce signaling overhead, the allowed beams may be indicated relatively to the triggered beam, e.g., RRC can configure that allowed beam indices are +-1 of the triggered beam. The option may be used where the index order follows spatial order of beams.

[0138] In some embodiments, the RRC configuration may comprise an offset or absolute threshold for the UE to continue with same SSB of early TA irrespective of whether that same SSB is best beam at the time of C-LTM or not. Otherwise the UE should trigger RACH-based C-LTM. An offset or threshold value may be provided by network, where the UE may use the same beam for sending RRC Reconfiguration Complete during execution, which was used for sending the preamble if the signaling strength of the beam is within the threshold (even where another beam has better signalling strength than this beam during execution).Reference is made to Fig.3 which schematically shows CS1-RS beam quasi colocated (QCL) with SSB beam.

[0139] In some embodiments, the UE measures a high signal quality of TCI 13(SSB1) of a candidate target cell.

[0140] The UE may be triggered to request early TA for TCI 13.

[0141] The UE receives information related to TCI 13, but also information related to TCI 14 and TCI 12. TCI 12 and TCI 13 have the same or the same TA value as TCI 13. This information enables the UE to perform RACH-less handover to TCI 14 and / or TCI 12 later. This may be when an execution condition is fulfilled. This will be without the need to request another early TA for TCI 12 or TCI 14, which would delay the handover. This is also without the need to do RACH-based handover, which would also delay the handover.

[0142] Reference is made to Fig.4 which shows a first example procedure of some embodiments. In this example, potential beams are shared in a MAC-CE. In this example, the beams are shared along with TA information.

[0143] As referenced by 1, a message which contains a L3 measurement report is received by the source DU of the source cell from the UE.

[0144] As referenced by 2, an UL RRC message transfer is sent from the source DU to the CU. This UL RRC message transfer contains the received L3 measurement report.

[0145] As referenced by 3, at the CU, the L3 measurement report is analysed by the CU and this measurement report triggers a LTM candidate preparation.

[0146] As referenced by 4, a request for the set-up of a UE context, a UE context setup request, is sent from the CU to the target DU. This request comprises a candidate cell.

[0147] As referenced by 5, a response to the UE context setup request, a UE context setup response, is sent from the target DU to the CU.

[0148] As referenced by 6, a request for a modification of the UE context, a UE context modification request, is sent from the CU to the source DU.

[0149] As referenced by 7, a response to the UE context modification request, a UE context modification response, is sent from the source DU to the CU.

[0150] It should be appreciated that there maybe modification of aUE context between the CU and the target DU(s). This may be to provide configuration for when the target DU(s) become the serving DU. This may enable subsequent LTM.

[0151] As referenced by 8, the CU generates a RRC reconfiguration to be sent to the UE. This RRC reconfiguration may relate to the measurement configuration of LI cell change.This RRC reconfiguration may relate to configuration of prepared cells. The RRC reconfiguration message may comprises LTM candidate configurations The RRC reconfiguration message may provide one or more conditions for conditional LTM cell switch execution. The RRC Reconfiguration message may optionally comprise one or more of conditions for triggering early TA acquisition, preambles for early TA acquisition, and CFRA-based cell switch.

[0152] As referenced by 9, the CU sends a DL RRC message transfer to the source DU. The DL RRC message transfer may comprise the RRC reconfiguration, as previously discussed.

[0153] As referenced by 10, the source DU, forwards to the UE the RRC reconfiguration, as previously discussed, The UE may store the LTM candidate configurations.

[0154] As referenced by 11, the UE sends a RRC reconfiguration complete message to the source DU,

[0155] As referenced by 12, an UL RRC message transfer containing the RRC reconfiguration complete is sent from the source DU to the CU.

[0156] As referenced by 13, the UE sends an LI Measurement report to the source DU. As referenced by 14, the UE performs DL synchronization with the candidate cell(s) before receiving the cell switch command.

[0157] As referenced by 15, an early TA decision is made at the network.

[0158] As referenced by 16, a PDCCH order is sent from the source DU to the UE. This PDDCH order indicating the preamble to be used by the UE for the early TA acquisition procedure.

[0159] As referenced by 17, the UE sends preamble towards the indicated candidate cell -that is target DU. This is for early TA acquisition. The preamble is a RACH (random access channel) preamble.

[0160] As referenced by 18, based on the preamble, the TA of the target cell is derived by the target DU and sent to the CU. Along with the TA, TCI states of the current beam and neighbouring beams are also communicated to the CU with the respective SSB Id. For example, the TCI states of the neighbouring two beams on both sides of the current beam are sent to the CU.

[0161] As referenced by 19, the CU sends the TA value and TCI states of the current beam and neighbouring beams to the source DU. The associated SSB-id is provided with each TCI state.As referenced by 20, the source DU informs the UE of the TA for the target cell and TCI states of the current and neighbouring beams using a MAC CE.

[0162] As referenced by 21, the execution condition (for example, received earlier in the part of the procedure referenced 10) is met. The UE chooses a best beam of the target cell. This may be a beam have a best signal quality.

[0163] A first case, Case 1 will now be considered:

[0164] As referenced by 22, if the SSB-ld of the selected best beam was shared earlier, the cell switch is triggered by the UE to the target cell using the selected TCI state / SSB / beam.

[0165] As referenced by 23, the UE sends a message, RRC reconfiguration complete, that the RRC reconfiguration is complete to the target DU using the cell-switched target cell.

[0166] As referenced by 24, an UL RRC message transfer is sent from the target DU to the CU. The UL RRC message transfer contains the RRC Reconfiguration complete.

[0167] As referenced by 25, an access notification is sent from the target DU to the CU. A second case, Case 2, will now be considered:

[0168] As referenced by 26, if the selected best beam is not within the earlier shared SSB Ids, the UE selects the best beam among the earlier shared SSB Ids that meets the cell change condition.

[0169] The parts of the procedure referenced 27 to 29 are as described in relation to the parts of the procedure referenced 23 to 25.

[0170] Both the first and second cases are RACH-less handover. In other words, it is not necessary to perform a RACH procedure in order to handover to the target cell.

[0171] A third case, case 3 will now be considered.

[0172] If the SSB-ld of the selected best beam was not shared earlier and none of the earlier shared beams / SSB-lds meet the cell change condition, a random-access process using the CFRA preamble is initiated.

[0173] The parts of the procedure referenced 31 to 30 are as described in relation to the parts of the procedure referenced 23 to 25.

[0174] Regardless of which case applies, as referenced by 34, the CU sends a command to release the context of the UE to the source DU.

[0175] As referenced by 35, the source DU sends a message to the CU indicating that that the release of the context of the UE has been completed.

[0176] As referenced by 36, the path switch procedure is completed.Reference is made to Fig.5 which shows a second example procedure of some embodiments. In this example, potential beams are shared in a MAC-CE. In this example, the beams are sent in different MAC CE to that providing TA information.

[0177] The parts of the procedure referenced 1 to 19 are the same as the parts of the procedure referenced 1 to 19 in Fig.4.

[0178] As referenced by 20, the source DU informs the UE of the TA for the target cell using a MAC CE.

[0179] As referenced by 21, the source DU informs the UE of the TCI states of current and neighbouring beams using a MAC CE.

[0180] The parts of the procedure reference 22 to 37 correspond to the part of the procedure referenced 21 to 36 of Fig.4.

[0181] Reference is made to Fig.6 which shows a third example procedure of some embodiments. In this example, potential beams are shared in a RRC reconfiguration message.

[0182] The parts of the procedure referenced 1 to 8 are the same as the parts of the procedure referenced 1 to 8 in Fig.4.

[0183] In the part of the procedure referenced 9, the CU sends DL RRC message transfer containing RRC reconfiguration to the source DU. This is for forwarding to the UE.

[0184] The RRC reconfiguration message may comprise conditions for conditional LTM cell switch execution.

[0185] Optionally, the RRC reconfiguration message may comprise conditions for triggering early TA acquisition, and preambles for early TA acquisition and CFRA-based cell switch.

[0186] The RRC reconfiguration message may comprise neighbour or allowed SSB-beam-IDs for each TCl-State / SSB-beam.

[0187] In the part of the procedure referenced by 10, the RRC reconfiguration (is forwarded from source DU to the UE.

[0188] The parts of the procedure referenced 11 to 17 are the same as the parts of the procedure referenced 11 to 17 in Fig.4.

[0189] As referenced by 18, based on the preamble, the TA of the target cell is derived by target DU and sent to the CU.

[0190] As referenced by 19, the CU sends the TA value to the source DU.

[0191] As referenced by 20, the source DU informs the UE of the TA for the target cell and the current TCI State using a MAC CE.The parts of the procedure referenced 21 to 36 are the same as the parts of the procedure referenced 21 to 36 in Fig.4.

[0192] Reference is made to Figs. 7 to 10 which shows some methods of some example embodiments. The method may be performed by an apparatus.

[0193] The apparatus may comprise suitable means, such as circuitry for providing the respective method.

[0194] Alternatively or additionally, the apparatus may comprise at least one processor and at least one memory storing instructions that, when executed by the at least one processor cause the apparatus at least to provide the respective method.

[0195] Alternatively or additionally, the apparatus may be such as discussed in relation to Fig. 11.

[0196] The respective methods may be provided by computer program code or computer executable instructions.

[0197] Reference is made to Fig. 7. The method may be performed by an apparatus. The apparatus may be or provided in a user equipment or terminal device.

[0198] The method comprises as referenced Al, establishing a connection via a source cell provided by a radio access network.

[0199] The method comprises as referenced A2, receiving, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition.

[0200] The method comprises as referenced A3, measuring the signal quality of at least one beam of at least one target candidate cell.

[0201] The method comprises as referenced A4, determining to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell.

[0202] The method comprises as referenced A5, receiving, via the source cell, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to a measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the apparatus.

[0203] The method comprises as referenced A6, monitoring the execution condition, and in response to determining that the execution condition is fulfilled, selecting a beam forhandover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0204] Reference is made to Fig. 8. The method may be performed by an apparatus. The apparatus may be or provided in a network node. The network node may be an access node. The apparatus may be or provided in a distributed unit of a base station.

[0205] The method comprises as referenced Bl, establishing a connection with a user equipment.

[0206] The method comprises as referenced B2, transmitting to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition.

[0207] The method comprises as referenced B3, receiving a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell.

[0208] The method comprises as referenced B4, making an early timing advance decision and send to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure.

[0209] The method comprises as referenced B5, transmitting to the user equipment, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to a measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the user equipment.

[0210] Reference is made to Fig. 9. The method may be performed by an apparatus. The apparatus may be or provided in a user equipment or terminal device.

[0211] The method comprises as referenced Cl, establishing a connection via a source cell provided by a radio access network.

[0212] The method comprises as referenced C2, receiving, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information related to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell.

[0213] The method comprises as referenced C3, measuring a signal quality of at least onebeam of at least one target candidate cell.

[0214] The method comprises as referenced C4, determining to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell.

[0215] The method comprises as referenced C5, monitoring the execution condition. The method comprises as referenced C6, in response to determining that the execution condition is fulfilled, selecting a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

[0216] Reference is made to Fig. 10. The method may be performed by an apparatus. The apparatus may be or provided in a network node. The network node may be an access node. The apparatus may be or provided in a distributed unit of a base station.

[0217] The method comprises as referenced DI, establishing a connection with a user equipment.

[0218] The method comprises as referenced D2, transmitting to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition, the configuration further comprising beam information of a potential target candidate cell beam to be measured, and further beam information related to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the potential target candidate cell.

[0219] The method comprises as referenced D3, receiving a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell.

[0220] The method comprises as referenced D4, making an early timing advance decision. The method comprises as referenced D5, sending to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure.

[0221] It should be appreciated that the method described in relation to Figs. 7 to 10 may be modified to include one or more of the features discussed in relation to the previous examples.

[0222] Fig. 11 shows, by way of example, a block diagram of an apparatus 10. The apparatus 10 comprises, for example, at least one processor 12 and at least one memory 14 storing instructions 15 that, when executed by the at least one processor, cause the apparatus 10 at least to perform the method or methods as disclosed herein, and any of theembodiments thereof. In an example, the at least one memory and the instructions (e.g. a computer program code, software), are configured, with the at least one processor, to cause the apparatus 10 to perform the method or methods as disclosed herein, and any of the embodiments thereof.

[0223] A processor 12 may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a user equipment, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessors) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. 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 merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0224] The memory 14 may be implemented using any suitable data storage technology. The memory may comprise a database for storing data. The memory 14 may be at least in part external to apparatus 10 but accessible to apparatus 10.

[0225] The instructions 15 may be comprised in a computer readable medium or a non-transitory computer readable medium. A term non-transitory, as used herein, is a limitation of the medium itself (i.e. tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. random access memory, RAM, vs. read only memory, ROM).

[0226] For example, the apparatus 10 is a terminal device, such as the UE of Fig. 1. As another example, the apparatus is comprised in such a terminal device, e.g. as a chipsetconfigured to control the terminal device. The apparatus 10 maybe caused or configured to perform at least the method of Figs.7 or 9 and / or any one or more of the embodiments described.

[0227] As another example, the apparatus 10 is a network node, e.g. the network node of Fig. 1. The apparatus may comprise a source DU. In another embodiment, the apparatus is comprised in such a network node, e.g. as a chipset configured to control the network node. The apparatus 10 may be caused or configured to perform at least the method of Figs. 8 or 10 and / or any one or more of the embodiments described.

[0228] The apparatus may comprise one or more entities of any of protocol layers, such as a MAC entity, an RRC entity, an RLC entity, a PDCP entity or a PHY entity.

[0229] The apparatus 10 comprises a radio interface 16. The radio interface 16 may provide the apparatus 10 with communication capabilities. The radio interface 16 may comprise a receiver configured to receive information in accordance with at least one cellular or non-cellular standard. The radio interface 16 may comprise a transmitter configured to transmit information in accordance with at least one cellular or non-cellular standard. The receiver may comprise more than one receiver. The transmitter may comprise more than one transmitter. The radio interface 16 may comprise a transceiver configured to receive and transmit information in accordance with at least one cellular or non-cellular standard. The transceiver may comprise more than one transceiver.

[0230] The apparatus 10 may comprise a user interface 18 comprising, for example, at least one of a keypad, a microphone, a touch display, a display, a speaker, etc. The user interface 18 may be used to control the apparatus by the user. The user interface 18 may be external to the apparatus 10. For example, the apparatus 10 may be connected to another device, such as a computer, either via wireless or wired connection, and the apparatus 10 is controlled by the user via the computer.

[0231] In an embodiment, at least some of the processes described herein may be carried out by an apparatus comprising means for carrying out at least some of the described processes. Means for performing method steps as disclosed herein may include software and / or hardware components of the apparatus 10. For example, the at least one processor 12, the memory 14, and the computer program code form means for carrying out the method or methods as disclosed herein, and any of the embodiments thereof. As used herein the term “means” is to be construed in singular form, i.e. referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore,terminology “means for [performing A, B, C]”, is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology “means for performing A, means for performing B, means for performing C” is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C.

[0232] Even though the invention has been described above with reference to examples according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly, and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.

Claims

CLAIMS1. An apparatus comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:establish a connection via a source cell provided by a radio access network. receive, via the source cell, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition;measure a signal quality of at least one beam of at least one target candidate cell;determine to transmit an early timing advance request towards a target candidate cell for a measured beam and for handover preparation from the source cell to the target candidate cell;receive, via the source cell, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to the measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the apparatus; and monitor the execution condition, and in response to determining that the execution condition is fulfilled, select a beam for handover based on the received beam information and respective signal quality of measured beams, wherein a random access channel, RACH, less handover is prioritized.

2. The apparatus as claimed in claim 1, wherein selecting a beam for handover comprises determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam being one of the at least one potential neighbour beam, selecting that best beam as the beam for handover.

3. The apparatus as claimed in any preceding claim, wherein selecting a beam for handover comprises determining a best beam from the measured beams based on the respective signal quality, and responsive to the best beam not being one of the at least one potential neighbour beam, determining if one or more of the at least one potentialneighbour beam satisfy the execution condition.

4. The apparatus as claimed in claim 3, wherein when it is determined that one or more of the at least one potential neighbour beam satisfy the execution condition, selecting one of the at least one potential neighbour beam satisfying the execution condition as the beam for handover.

5. The apparatus as claimed in claim 3, wherein when it is determined that no one of the at least one potential neighbour beam satisfy the execution condition, the instructions, when executed by the at least one processor, further cause the apparatus to perform a random-access procedure.

6. The apparatus as claimed in any preceding claim, wherein the MAC CE message further comprises timing advance information for the target candidate cell.

7. The apparatus as claimed in any of claims 1 to 5, wherein the instructions, when executed by the at least one processor, further cause the apparatus to receive a further MAC CE message, said further MAC CE message comprising timing advance information for the target candidate cell.

8. The apparatus as claimed in any preceding claim, wherein the information related to the measured beam of the target candidate cell and to the at least one potential neighbour beam comprises one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.

9. The apparatus of any of claims 1 to 8, wherein the apparatus is or is comprised in a user equipment.

10. An apparatus comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to:establish a connection with a user equipment;transmit to the user equipment, a configuration related to a conditional lower layer triggered mobility, LTM, the configuration comprising an execution condition;receive a measurement report from the user equipment comprising a signal quality of at least one beam of at least one target candidate cell;make an early timing advance decision;send to the user equipment a preamble to be used by the user equipment for an early timing advance acquisition procedure; andtransmit to the user equipment, a medium access control control element, MAC CE, message, said MAC CE message comprising information related to a measured beam of the target candidate cell and to at least one potential neighbour beam having a timing advance value which is the same as that of the beam of the target candidate cell, and for which no early timing advance request has been submitted by the user equipment.

11. The apparatus as claimed in claim 10, wherein the MAC CE message further comprises timing advance information for the target candidate cell.

12. The apparatus as claimed in claim 10, wherein the instructions, when executed by the at least one processor, further cause the apparatus to transmit a further MAC CE message, said further MAC CE message comprising timing advance information for the target candidate cell.

13. The apparatus as claimed in claim 10, 11 or 12, wherein the information related to the measured beam of the target candidate cell and to the at least one potential neighbour beam comprises one or more of a respective transmission configuration indicator, TCI, or a respective synchronization signal block, SSB, identity.

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