Low layer triggered mobility procedure enhancement

Abstract

Embodiments of the present disclosure relates to the field of telecommunication and in particular to devices, methods, apparatuses and computer readable storage medium for more low layer triggered mobility procedure enhancement. The apparatus (i.e., the user device 100) is configured to perform receiving, from a network device, an indication indicative of time duration to keep track of at least one synchronization related to at least one transmission configuration indicator (TCI) state; activating the at least one TCI state during a mobility procedure; and keeping track of the at least one synchronization related to the at least one TCI state based on the time duration.

Description

LOW LAYER TRIGGERED MOBILITY PROCEDURE ENHANCEMENTFIELD

[0001] Embodiments of the present disclosure relates to the field of telecommunication and in particular to devices, methods, apparatuses and computer readable storage medium for more low layer triggered mobility procedure enhancement.BACKGROUND

[0002] Wireless networks require minimal interruption during user equipment (UE) mobility, especially for demanding applications like ultra-reliable low latency communication (URLLC) and enhanced mobile broadband (eMBB). Traditional handover mechanisms in 5G rely on UE measurements and signaling, which can introduce latency. To address this, 3GPP Release 18 is exploring a new approach called "L1 / L2 inter-cell mobility". This method utilizes lower layer (L1) measurements and signaling to trigger handover directly from the Medium Access Control (MAC) layer, aiming to reduce handover interruption time compared to the baseline method. This solution will be supported in both frequency range 1 (FR1) and frequency range 2 (FR2) frequency bands for 5G Advanced networks.SUMMARY

[0003] The scope of protection sought for various example embodiments is set out by the claims. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the claims are to be interpreted as examples useful for understanding various embodiments.

[0004] Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, byway of example, the principles of embodiments of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Embodiments of the disclosure are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings.

[0006] FIG. 1 illustrates an example of a wireless communication network;

[0007] FIG. 2 illustrates one of examples of LTM signaling procedures.

[0008] FIG. 3(a) illustrates examples of the time duration and FIG. 3(b) illustrates concepts of the time duration when PDCCH order is transmitted.

[0009] FIG. 4 illustrates embodiments of the first aspect of the disclosure.

[0010] FIG. 5 illustrates one of embodiments of the first aspect of the disclosure.

[0011] FIG. 6 illustrates one of embodiments of the first aspect.

[0012] FIG. 7 illustrates embodiments of the second aspect of the disclosure.

[0013] FIG. 8 illustrates one of embodiments of the second aspect of the disclosure.

[0014] FIG. 9 illustrates embodiments of the first aspect of the disclosure.

[0015] FIG. 10 illustrates one of embodiments of the third aspect of the disclosure.

[0016] FIG. 11 illustrates an example of an apparatus 1100.

[0017] FIG. 12 illustrates an example of an apparatus 1200.

[0018] Throughout the drawings, the same or similar reference numerals may represent the same or similar element.DETAILED DESCRIPTION

[0019] The following embodiments are exemplifying. Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein may be implemented in various manners other than the ones described below.

[0020] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein may have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0021] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, element or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, element or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, element or characteristic in connection with other embodiments whether or not explicitly described.

[0022] 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. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms. For example, “A and / or B” stands for one of A, B, and A and B.

[0023] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined 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 the elements.

[0024] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0025] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0026] 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 mobile phone or server, to perform various functions) and(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) 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.

[0027] 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 merelya 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.

[0028] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-loT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G), the sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0029] As used herein, the term “network entity” refers to a node in a communication network via which a user device accesses the network and receives services therefrom. The network entity may refer to a network device, a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a radio access network (RAN) node, a new generation RAN (NG-RAN) node, a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (I AB) node, a low power node such as a femto, a pico, 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, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture includes a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IAB node includes a Mobile Terminal (IAB-MT) part that behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

[0030] The term “user device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), a terminal device or an Access Terminal (AT). The user device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, awearable 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, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a headmounted 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. The user device may also correspond to a Mobile Termination (MT) partofan I AB node (e.g., a relay node). In the following description, the terms “user device”, “communication device”, “terminal”, “terminal device”, “user equipment” and “UE” may be used interchangeably.

[0031] As used herein, the term “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” “downlink resource” or “sidelink resource” may refer to any resource for performing a communication, for example, a communication between a user device and a network entity, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0032] FIG. 1 depicts an example of a simplified wireless communication network showing some physical and logical network entities. The connections shown in FIG. 1 may be physical connections or logical connections. It is apparent to a person skilled in the art that the wireless communication network may also comprise other physical and logical entities than those shown in FIG. 1 A.

[0033] The example embodiments described herein are not, however, restricted to the wireless communication network given as an example but a person skilled in the art may apply the embodiments described herein to other wireless communication networks provided with necessary properties.

[0034] The example wireless communication network shown in FIG. 1 includes an access network, such as a radio access network (RAN), and a core network 110.

[0035] FIG. 1 shows user equipment (UE) 100, 102 configured to be in a wireless connection on one or more communication channels in a radio cell with an access node (AN) 104 of an access network. The AN 104 may be an evolved NodeB (abbreviated as eNB or eNodeB), or a next generation evolved NodeB (abbreviated as ng-eNB), or a next generation NodeB (abbreviated as network device 104 or gNodeB),providing the radio cell. The wireless connection (e.g., radio link) from a UE to the access node 104 may be called uplink (UL) or reverse link, and the wireless connection (e.g., radio link) from the access node to the UE may be called downlink (DL) or forward link. UE 100 may also communicate directly with UE 102, and vice versa, via a wireless connection generally referred to as a sidelink (SL). It should be appreciated that the access node 104 or its functionalities may be implemented by using any node, host, server or access point etc. entity suitable for providing such functionalities.

[0036] The access network may comprise more than one access node, in which case the access nodes may also be configured to communicate with one another over links, wired or wireless. These links between access nodes may be used for sending and receiving control plane signaling and also for routing data from one access node to another access node.

[0037] The access node may comprise a computing device configured to control the radio resources of the access node. The access node may also be referred to as a network device, a network entity, a base station, a base transceiver station (BTS), an access point, a cell site, a radio access node or any other type of node capable of being in a wireless connection with a UE (e.g., UEs 100, 102). The access node may include or be coupled to transceivers. From the transceivers of the access node, a connection may be provided to an antenna unit that establishes bi-directional radio links to UEs 100, 102. The antenna unit may comprise an antenna or antenna element, or a plurality of antennas or antenna elements.

[0038] The access node 104 may further be connected to a core network (CN) 110. The core network 110 may comprise an evolved packet core (EPC) network and / or a 5th generation core network (5GC). The EPC may comprise network entities, such as a serving gateway (S-GW for routing and forwarding data packets), a packet data network gateway (P-GW) for providing connectivity of UEs to external packet data networks, and a mobility management entity (MME). The 5GC may comprise network functions, such as a user plane function (UPF), an access and mobility management function (AMF), and a location management function (LMF).

[0039] The core network 110 may also be able to communicate with one or more external networks 113, such as a public switched telephone network or the Internet, or utilize services provided by them. For example, in 5G wireless communication networks, the UPF of the core network 110 may be configured to communicate with an external data network via an N6 interface. In LTE wireless communication networks, the P-GW of the core network 110 may be configured to communicate with an external data network.

[0040] The illustrated UE 100, 102 is one type of an apparatus to which resources on the air interface may be allocated and assigned. The UE 100, 102 may also be called a wireless communication device, a subscriber unit, a mobile station, a remote terminal, an access terminal, a user terminal, a terminal device, or a user device just to mention but a few names. The UE may be a computing device operating with orwithout a subscriber identification module (SIM), including, but not limited to, the following types of computing devices: a mobile phone, a smartphone, a personal digital assistant (PDA), a handset, a computing device comprising a wireless modem (e.g., an alarm or measurement device, etc.), a laptop computer, a desktop computer, a tablet, a game console, a notebook, a multimedia device, a reduced capability (RedCap) device, a wearable device (e.g., a watch, earphones or eyeglasses) with radio parts, a sensor comprising a wireless modem, or any computing device comprising a wireless modem integrated in a vehicle.

[0041] It should be appreciated that a UE may also be a nearly exclusive uplink-only device, of which an example may be a camera or video camera loading images or video clips to a network. A UE may also be a device having capability to operate in an Internet of Things (loT) network, which is a scenario in which objects may be provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. The UE may also utilize cloud. In some applications, the computation may be carried out in the cloud or in another UE.

[0042] The wireless communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in FIG. 1 by “cloud” 114). The wireless communication network may also comprise a central control entity, or the like, providing facilities for wireless communication networks of different operators to cooperate for example in spectrum sharing.

[0043] 5G enables using multiple input - multiple output (MIMO) antennas in the access node 104 and / or the UE 100, 102, many more base stations or access nodes than an LTE network (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and / or spectrum available. 5G wireless communication networks may support a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control.

[0044] In 5G wireless communication networks, access nodes and / or UEs may have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also being integrable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, for example, as a system, where macro coverage may be provided by the LTE, and 5G radio interface access may come from small cells by aggregation to the LTE. In other words, a 5G wireless communication network may support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave - mmWave). One of the concepts considered to be used in 5G wireless communication networks may be network slicing, in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the substantially same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0045] In some example embodiments, an access node (e.g., access node 104) may comprise: a radio unit (RU) comprising a radio transceiver (TRX), i.e., a transmitter (Tx) and a receiver (Rx); one or more distributed units (DUs) 105 that may be used for the so-called Layer 1 (L1) processing and real-time Layer 2 (L2) processing; and a central unit (CU) 108 (also known as a centralized unit) that may be used for non-real-time L2 and Layer 3 (L3) processing. The CU 108 may be connected to the one or more DUs 105 for example via an F1 interface. Such an embodiment of the access node may enable the centralization of CUs relative to the cell sites and DUs, whereas DUs may be more distributed and may even remain at cell sites. The CU and DU together may also be referred to as baseband or a baseband unit (BBU). The CU and DU may also be comprised in a radio access point (RAP).

[0046] The CU 108 may be a logical node hosting radio resource control (RRC), service data adaptation protocol (SDAP) and / or packet data convergence protocol (PDCP), of the NR protocol stack for an access node. The DU 105 may be a logical node hosting radio link control (RLC), medium access control (MAC) and / or physical (PHY) layers of the NR protocol stack for the access node. The operations of the DU may be at least partly controlled by the CU. It should also be understood that the distribution of functions between DU 105 and CU 108 may vary depending on implementation. The CU may comprise a control plane (CU-CP), which may be a logical node hosting the RRC and the control plane part of the PDCP protocol of the NR protocol stack for the access node. The CU may further comprise a user plane (CU-UP), which may be a logical node hosting the user plane part of the PDCP protocol and the SDAP protocol of the CU for the access node.

[0047] Cloud computing systems may also be used to provide the CU 108 and / or DU 105. A CU provided by a cloud computing system may be referred to as a virtualized CU (vCU). In addition to the vCU, there may also be a virtualized DU (vDU) provided by a cloud computing system. Furthermore, there may also be a combination, where the DU may be implemented on so-called bare metal solutions, for example applicationspecific integrated circuit (ASIC) or customer-specific standard product (CSSP) system-on-a-chip (SoC).

[0048] Edge cloud may be brought into the access network (e.g., RAN) by utilizing network function virtualization (NFV) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a computing system operationally coupled to a remote radio head (RRH) or a radio unit (RU) of an access node. It is also possible that access node operations may be performed on a distributed computing system or a cloud computing system located at the access node. Application of cloud RAN architecture enables RAN real-time functions being carried out at the access network (e.g., in a DU 105) and non-real-time functions being carried out in a centralized manner (e.g., in aCU 108).

[0049] It should also be understood that the distribution of functions between core network operations and access node operations may differ in future wireless communication networks compared to that of the LTE or 5G, 6G, or even be non-existent. Some other technological advancements that may be used include big data and all-IP, which may change the way wireless communication networks are being constructed and managed. 5G (or new radio, NR) wireless communication networks may support multiple hierarchies, where multi-access edge computing (MEC) servers may be placed between the core network 110 and the access node 104. It should be appreciated that MEC may be applied in LTE wireless communication networks as well.

[0050] A 5G wireless communication network (“5G network”) may also comprise a non-terrestrial communication network, such as a satellite communication network, to enhance or complement the coverage of the 5G radio access network. For example, satellite communication may support the transfer of data between the 5G radio access network and the core network, enabling more extensive network coverage. Possible use cases may be providing service continuity for machine-to-machine (M2M) or Internet of Things (loT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway / maritime / aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano)satellites are deployed). A given satellite 106 in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay access node or by an access node 104 located on-ground or in a satellite.

[0051] It is obvious for a person skilled in the art that the access node 104 depicted in FIG. 1 is just an example of a part of an access network (e.g., a radio access network) and in practice, the access network may comprise a plurality of access nodes, the UEs 100, 102 may have access to a plurality of radio cells, and the access network may also comprise other apparatuses, such as physical layer relay access nodes or other entities. At least one of the access nodes may be a Home eNodeB or a Home gNodeB. A Home gNodeB or a Home eNodeB is a type of access node that may be used to provide indoor coverage inside a home, office, or other indoor environment. The access node 104 may be a network device.

[0052] Additionally, in a geographical area of an access network (e.g., a radio access network), a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which may be large cells having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The access node(s) of FIG. 1 may provide any kind of these cells. Acellular radio network may be implemented as a multilayer access network including several kinds of radiocells. In multilayer access networks, one access node may provide one kind of a radio cell or radio cells, and thus a plurality of access nodes may be needed to provide such a multilayer access network.

[0053] For fulfilling the need for improving performance of access networks, the concept of “plug-and-play” access nodes may be introduced. An access network which may be able to use “plug-and-play” access nodes, may include, in addition to Home eNodeBs or Home gNodeBs, a Home Node B gateway, or HNB-GW (not shown in FIG. 1). An HNB-GW, which may be installed within an operator’s access network, may aggregate traffic from a large number of; Home eNodeBs or Home gNodeBs back to a core network of the operator.

[0054] 1. LTM procedure

[0055] Hereinafter, a low layer triggered mobility (LTM) procedure that may be applied to the embodiments of the disclosure, is explained. The low layer may mean layer 1 (L1) and / or layer 2 (L2).

[0056] LTM is a procedure in which a gNB receives measurement report(s) from a UE. The LTM procedure may comprise an LTM cell switch procedure, where UE’s serving cell (PCell or PSCell) is switched by the network by sending the LTM cell switch command. An LTM switch command is currently assumed delivered by MAC signaling using a Medium Access Control Control Element (MAC CE). Hence, not using RRC signaling as a L3 based handover which is one of the current methods for changing between cells. LTM cell switch decision is currently assumed to be based on L1 measurements that are performed and reported using L1 measurement reports by the UE. Alternatively, if the target cell is an FR1 cell, LTM decision may be based on L3 measurements thathave been performed and reported by the UE. Measurements and reporting are based on LTM candidate cell configuration provided by the network for one or more LTM candidate cells. An LTM candidate cell may be neighboring cells or a UE’s current serving cells (e.g. SCel Is).

[0057] In Release-18 of 3GPP, LTM measurements on a neighboring candidate cell are performed using Synchronization Signal Blocks (SSBs, or Synchronized signals and PBCH blocks) transmitted by the candidate cell for which the SSB configuration is provided to the UE.

[0058] Before the cell switch, the network may optionally activate one or more Transmission Configuration Indicator (TCI) state(s) for one or more candidate cells. Once a candidate cell TCI state is activated the UE may start tracking the time / frequency synchronization using the reference signals associated with the activated TCI state(s). The UE may also perform early UL synchronization before the cell switch. The early UL synchronization may be performed if this is requested by the network either (1) through PDCCH ordered RACH procedure, where the UE sends preamble to the indicated target cell, based on which network estimates the TA and shares this to the UE in the cell switch command, or (2) through UE based TA estimation,where the network configures the UE to autonomously estimate the TA of one or more candidate cells to be used after cell switch. The LTM procedure can be used to reduce the cell switch delay and the mobility latency.

[0059] FIG. 2 illustrates one of examples of LTM signaling procedures.

[0060] The user device may be the UE 100, 102 of FIG.1 and the network device may be the AN 104 or the satellite 106. The AN or satellite may be the gNB. Hereinafter, the UE 100, 102 and the AN 104 or satellite 106 are referred to a user device 100 and network device 104, for consistency of the terms.

[0061] Refer to FIG. 2, the LTM procedure comprises an LTM preparation process including steps S205-S220, an LTM execution process including steps S225-S245, and an LTM completion process including step S250.

[0062] At step S205, the user device 100 is in a RRC connected state (RRC_CONNECTED) which is defined in 3GPP specifications.

[0063] At step S210, the user device 100 may send an L3 RRC Measurement Report message to the network device 104. The network device 104 may decides to configure LTM and initiates LTM preparation.

[0064] At step S215, the network device 104 may transmit an RRC Reconfiguration message to the UE including the LTM candidate configurations.

[0065] At step S220, the user device 100 may store the LTM candidate configurations and transmit an RRC Reconfiguration Complete message to the network device 104.

[0066] At step S225, in a first option, the user device 100 may perform L1 measurements on the configured LTM candidate cell(s) and transmit L1 measurement reports (L1 CSI report) to the network device 104. In another option, the user device 100 may perform L3 measurements on the configured LTM candidate cell(s) and transmit another RRC Measurement Report to initiate LTM execution. The L1 and L3 measurements should be performed as long as RRC reconfiguration (S215) is applicable.

[0067] At step S230, the user device 100 may perform early synchronization with the LTM candidate cell(s).

[0068] For example, the user device 100 performs early DL synchronization with the LTM candidate cell (s) before receiving the cell switch command. The user device 100 may activate and deactivate TCI states of LTM candidate cell(s), as triggered by the network device 104 with a TCI state activation (MAC CE).

[0069] Additionally, after completion of early DL synchronization at S230, the user device 100 may perform early UL synchronization with LTM candidate cell(s) before receiving the cell switch command, by using UE-based TA measurement, if configured. Alternatively, the user device 100 may perform the early UL synchronization by transmitting a preamble towards the candidate cell, as triggered by the network node 104.

[0070] When UE-based TA measurement is configured, user device 100 acquires the TA value(s) of the candidate cell(s) by measurement. The user device 100 performs early TA acquisition with the candidate cell(s) as requested by the network device 104 before receiving the cell switch command as specified in clause 9.2.6 of TS 38.300. This is done via a contention free random access (CFRA) triggered by a PDCCH order (DCI) from the source cell, following which the UE sends preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell due to CFRA towards the candidate cell(s), the user device 100 does not receive random access response from the network for the purpose of TA value acquisition and the TA value of the candidate cell is indicated in the cell switch command. The user device 100 does not maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

[0071] At step S235, the network device 104 may decide to execute cell switch to a target cell and transmit an LTM cell switch command (MAC CE) triggering cell switch by including a target configuration ID which indicates the index of the candidate configuration of the target cell, a beam indicated with a TCI state, or beams indicated with DL and UL TCI states, and a timing advance command for the target cell, if available. The user device 100 may switch to the target cell and apply the candidate configuration indicated by the target configuration ID.

[0072] At step S240, the user device 100 may perform the random access procedure towards the target cell, if UE does not have valid TA of the target cell as specified in clause 5.18.35 ofTS 38.321.

[0073] At step S245, the user device 100 may complete the LTM cell switch procedure by sending RRC Reconfiguration Complete message to target cell. If the user device 100 has performed a RA procedure in step S240, the user device 100 may consider that LTM cell switch execution is successfully completed when the random access procedure is successfully completed. For RACH-less LTM, the user device 100 may consider that LTM cell switch execution is successfully completed when the user device 100 determines that the network has successfully received its first UL data.

[0074] The steps S225-S245 (i.e., LTM execution process) can be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration(s) provided in S215.

[0075] The procedure over the air interface described in Figure 9.2.3.5.2-1 of TS 38.300 may be applicable to both intra-gNB-DU LTM and inter-gNB-DU LTM. The overall LTM procedures over F1-C interface are captured in TS 38.401.

[0076] The embodiments of the present disclosure may be applied to the LTM procedure.

[0077] 2. Early DL synchronization process

[0078] The early DL synchronization process may be performed at step S230 of FIG.2. The early DL synchronization process may be referred to as an early TCI state activation.

[0079] When supported by the user device 100, it is possible to activate TCI state(s) of one or multiple LTM candidate cells before sending the cell switch command. This early TCI activation allows the user device 100 to be DL synchronized with those cells associated with an activated TCI state, thereby facilitating a faster cell switch to one of those candidate cells when cell switch is triggered. If the TCI state of the candidate cell is not activated before the cell switch, the TCI state activation happens with the cell switch command. An additional delay is then added to the switch delay as the user device needs time for fine time tracking in the candidate cell.

[0080] RAN4 has defined early TCI state activation delay requirements in section 8.25 of TS 38.133. The delay is the time from when the user device receives the TCI state activation command to the time user device has completed the activation, including fine DL synchronization (if needed). After TCI state activation is completed, if the network sends a cell switch command, the user device is expected to have fine DL synchronization with the TCI state, and hence the user device is not given time for DL synchronization during the cell switch under certain conditions defined in cell switch delay requirements in section 6.3 of TS 38.133.

[0081] For future release (e.g., Rel-19), an embodiment of the disclosure proposes a UE autonomous TCI activation (i.e. without a TCI state activation command from the network node). Such UE autonomous TCI activation could happen for a TCI state given in LTM candidate cell configuration for example when some configured (signal based or other) condition is met.

[0082] The early DL synchronization during the LTM procedure and the UE autonomous TCI state activation may be applied to the embodiments of the disclosure.

[0083] 3. Time duration

[0084] Hereinafter, a definition of time duration (Tmamtam) that is applied to the embodiments of the disclosure is explained.

[0085] FIG. 3(a) illustrates examples of the time duration and FIG. 3(b) illustrates concepts of the time duration when PDCCH order is transmitted.

[0086] In one example, an indication is used to indicate a time duration, such as Tmamtam, and the time duration is indicated as one of:- number of slots;- absolute value in milliseconds (for instance, 320ms);- multiple of SSB or CSI-RS periodicity (for instance, 5*Trswhere a user device (e.g., UE) is maintaining the DL synchronization of the activated TCI state);- Derived from DRX periodicity, for instance 3 * DRX duration.

[0087] Trs may represent a SS / PBCH Block Measurement Timing Configuration (SMTC) periodicity of a target NR cell (e.g., candidate cell), if the UE has been provided with an SMTC configuration for the target cell in a handover command. Otherwise, Trsmay be the SMTC configured in the measObjectNR IE having the same SSB frequency and subcarrier spacing. If the measObjectNR lEs having the same SSB frequency and subcarrier spacing configured by a master node (MN) and a secondary node (SN) have different SMTC, the Trs may be the periodicity of one of the SMTCs. If the UE is not provided with the SMTC configuration or measurement object on this frequency, the requirements are applied with Trs= 5ms, assuming the SSB transmission periodicity is 5ms. There is no requirement if the SSB transmission periodicity is not 5ms. If the UE has been provided with a higher layer in TS38.331 signaling (e.g., RRC signaling) of smtc2 prior to the handover command, Trsmay follow smtd or smtc2 according to the physical cell ID of the target candidate cell.

[0088] Referring to FIG. 3(a), a starting point (1) of the time indication may be after the reception and / or decoding (or, processing) of the TCI state activation command.

[0089] Alternatively, a starting point (2) of the time indication may be after the activation delay of the TCI state. The activation delay may include the processing time of the first reference signal (e.g., SSB).

[0090] Alternatively, a starting point (3) of the time indication may be the reception and / or processing of the first reference signal (e.g., SSB) associated with the TCI state activation command.

[0091] FIG. 3(b) shows special behaviour of the time duration related to the PDCCH order. The time duration (Tmamtam) may have a special behaviour once the PDCCH ordered RACH is triggered for the same candidate cell as the TCI state has been activated. For example:- (a) Tmamtam is continued over PDCCH ordered RACH as continuous time- (b) Tmaintain is suspended for the duration of PDCCH ordered RACH- (c) T maintain is restarted at the reception of PDCCH order- (d) Tmamtam is restarted after the completion of PDCCH ordered RACH- (e) Tmamtam is restarted at the PDCCH ordered RACH preamble transmission

[0092] In FIG. 3, an ending point of the time duration may be determined as:- the time point which UE has fully received the cell switch command;- the time point which UE has fully received the cell switch command and processed the cell switchcommand;- the time point when the first component of the cell switch command that causes interruption to the serving cell; or- time point at the end of the cell switch command, or the first uplink transmission on the target cell.

[0093] The time duration is a value that the user device (UE) would indicate which TCI states it continues to keep track synchronization of longer time. The UE may do such selection based on its current capability to keep track of DL sync for one or more TCI states for a longer period than the cell switch delay requirement as explained above. The user device may for example select at least one of the activated TCI states for longer maintenance time (Tmamtam) and inform the network device about it.

[0094] The definitions of the time duration explained above may be applied to the embodiments of the disclosures to be explained hereinafter.

[0095] 4. Keeping track of synchronization

[0096] In Rel-18 LTM, according to RAN4 cell switch delay requirements, in the case when the UE (e.g., user device) is configured with L1 measurements for an LTM candidate cell, and a TCI state is activated before cell switch command for a candidate cell, the UE is only required to have fine DL sync based on early TCI state activation if:- the time from completing the TCI state activation is not more than 160 ms; or- the measurement period for the SSB associated to the target TCI state is up to 160 ms.

[0097] When 1) the UE is not configured with L1 measurements and 2) LTM cell switch is triggered based on L3 measurements, according to the tentative requirement in square brackets, the UE is only required to have fine DL sync based on early TCI state activation if:- the time from completing the TCI state activation is not more than [480 ms]

[0098] More specifically, the requirement in all scenarios based on TS 38.133 version 18.7.0 may be referred to Table 1.

[0099] [Table 1]_

[0100] If the conditions shown Table 1 are not met, the UE is allowed to do fine DL synchronization during the cell switch, which means that TCI state activation did not provide any reduction to the cell switch interruption.

[0101] The problem with the requirement described in Table 1 is that if some UEs would be able to keep track of the DL timing (i.e., synchronization) based on TCI state activation for a longer time or under less restricted conditions than the requirement states, the network (e.g., gNB) does not know this longer time or less restricted conditions. The network can only assume that the UE stops keeping track of the DLsynchronization after 160 ms, if the measurement period is longer than 160 ms.

[0102] This limits the implementation of LTM, where the network is forced to send the TCI state activation command only a very short time before the cell switch in most scenarios to get the benefits of lower handover (HO) interruption time with early DL synchronization.

[0103] Considering that the requirement of Table 1 is a minimum requirement, it is expected that there to be UEs that are able to keep track of the DL synchronization based on early TCI state activation longer than the requirement states. However, the network does not know this and hence has to always expect that the UE loses track of DL synchronization after the 160 or 480 ms.

[0104] This is very limiting, and hence It is proposed that a UE supporting early TCI state activation for LTM candidate cells can inform about its capability to keep track of fine DL timing (e.g., synchronization) of a TCI state after TCI state activation is completed.

[0105] As a first aspect of the disclosure, a user device (e.g., UE) transmits the network device (e.g., gNB) UE capability information indicating how long the user device can keep track of the DL synchronization of a TCI state after TCI state activation command (see, Fig. 2 and sections 1 and 2) i.e. until cell switch or TCI state deactivation.

[0106] Additionally or alternatively, the user device may Inform the network device about time the user device is able to keep track of the DL synchronization of an activated TCI state. The values supported through this capability should be larger than the minimum requirement.

[0107] Additionally or alternatively, the user device informs through new dynamic signalling at the time of TCI state activation how long it can keep track of the DL synchronization of an activated TCI state.

[0108] As a second aspect of the disclosure, after TCI state is activated, a user device sends an indication to a network device (e.g., gNB) once the user device stops keeping track of the DL synchronization.

[0109] As a third aspect of the disclosure, the network device (gNB) indicates the user device (UE) how long the UE shall keep track of the DL synchronization of an activated TCI state after receiving the TCI state activation command e.g., through RRC (e.g. in LTM candidate cell(s) configuration) or MAC-CE (e.g. in TCI state activation command) signalling.

[0110] The first to third aspects of the disclosure can be implemented separately or in combination.

[0111] In addition, all embodiments of the disclosure may also apply for UE autonomous TCI state activation. The UE autonomous TCI state activation may be used for example for a conditional LTM, where the UE activates some of the configured TCI states autonomously (without network command) e.g. based on UE measurements. For example, the UE can activate a TCI state when event triggered reporting condition becomes met for a reference signal (e.g., SSB) associated to a TCI state. When the reporting conditionbecomes fulfilled, the UE could activate one or more associated TCI states.

[0112] Hereinafter the first to third aspects of the disclosure are explained more in detail. The explanations of FIGs. 1 to 3 and sections 1 and 2 may be applied to the embodiments of the first to third aspects of the disclosure.

[0113] 4.1 Embodiments of a first aspect of the disclosure

[0114] FIG. 4 illustrates embodiments of the first aspect of the disclosure.

[0115] The network environment comprises the user device 100 and the network device 104. The user device 100 may be the same entity as the UE (e.g., UE 100 or 102) of FIG. 1, 2 or 3, respectively. The network device 104 may be the same entity as the AN 104 or the satellite 106 of FIG. 1 , 2 or 3.

[0116] Regarding the user device 100, an apparatus for communication is to be explained. The apparatus may perform one of methods A1-A5 and A9-A15, and the apparatus may be the user device 100. Alternatively or additionally, the apparatus may be embedded in the user device 100.

[0117] 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 to perform one of methods A1-A5 and A9-A15 shown by FIG. 4.

[0118] The apparatus may comprise one or more means for performing one of methods A1-A5 and A9-A15.

[0119] Referring to FIG. 4, method A1 comprises step S410. At step S410, the apparatus (i.e., the user device 100) transmits capability information related to a mobility procedure to the network device 104. The capability information is indicative of a time duration (refer to section 3) on which the apparatus is able to keep track of at least one of synchronization related to at least one activated transmission configuration indicator (TCI) state. The at least one synchronization may be the early DL synchronization explained in FIG.2 and sections 1 and 2.

[0120] As a method A2, the apparatus of A1 has further caused to perform a step of receiving a capability enquiry message from a network device. The capability information may be transmitted in response to the capability enquiry message. The capability information may be transmitted during the UE capability exchange procedure.

[0121] As a method A3, the apparatus of A1 has further caused to perform a step of receiving a mobility related message from the network device. The capability information is transmitted in response to the mobility related message. The mobility related message may be a low layer triggered mobility (LTM) related message

[0122] As a method A4, the apparatus of A1 has further caused to perform a step of autonomously performing activation of one or more TCI states of at least one candidate cell. The capability information may further comprise an indication indicative of an autonomous TCI state activation of TCI state. The apparatus may transmit an indication indicative of the TCI state which has been autonomously activated TCI.

[0123] As a method A5, the at least one activated TCI state of A1 may comprise the one or more TCI states of A4.

[0124] Regarding the network device 104, an apparatus for communication is to be explained. The apparatus may perform one of methods A6-A8 and A9-A15, and the apparatus may be the network device 104. Alternatively or additionally, the apparatus may be embedded in the network device 104.

[0125] 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 to perform one of methods A6-A8 and A9-A15 shown by FIG. 4.

[0126] The apparatus may comprise one or more means for performing one of methods A6-A8 and A9-A15.

[0127] Referring to FIG. 4, the method A6 comprises step S410. At step S410, the apparatus receives capability information related to a mobility procedure. The capability information may be indicative of a time duration on which a user device 100 is able to keep track of at least one of synchronization related to at least one activated transmission configuration indicator (TCI) state.

[0128] As a method A7, the apparatus of A6 may be further caused to perform a step of transmitting a capability enquiry message to the user device 104. The capability information may be transmitted in response to the capability enquiry message.

[0129] As a method A8, the apparatus of A6 may be further caused to perform a step of transmitting a mobility related message. The capability information is transmitted in response to the mobility related message. The mobility related message may be a LTM related message to the user device.

[0130] As a method A9, the mobility procedure of any one of methods A1 to A8 is a low layer triggered mobility (LTM) procedure. The LTM procedure may comprise LTM execution procedure.

[0131] As a method A10, the LTM related message of the method A3 or A8 is one of a TCI state activation command and RRC reconfiguration message.

[0132] As a method A11, the capability information of any one of methods A1 to A10 may be further indicative of the at least one TCI state related to the time duration.

[0133] As a method A12, the capability information of any one of methods A1 to A11 may be determined based on at least one of a number of cells, a number of reference signal, or a frequency range at a time ofthe at least one activated TCI state has been activated.

[0134] As a method A13, the capability information of any one of methods A1 to A12 may be configured per at least one candidate cell or at least one TCI state of the at least one candidate cell.

[0135] As a method A14, the time duration of any one of methods A1 to A13 may be determined based on at least one measurement period of at least one reference signal associated with the at least one activated TCI state.

[0136] As a method A15, the time duration of any one of methods A1 to A14 may be represented in units of symbol, slot, or millisecond.

[0137] One of examples of the first aspect, the procedure (or the method) of FIG. 4 may be performed by using a computer program. The computer program may comprise instructions, which, when executed by the apparatus (e.g., the user device 100 or the network device 104), cause the apparatus to perform the methods explained by FIG.4.

[0138] One of examples of the first aspect, the computer-readable storage medium has stored thereon the computer program.

[0139] One of examples of the first aspect, a non-transitory computer readable medium has stored thereon the computer program.

[0140] FIG. 5 illustrates one of embodiments of the first aspect of the disclosure.

[0141] The network of FIG. 5 comprises the user device 100, the source network device 104, and the target network device 104a. The user device 100 may be the same entity as the UE (e.g., UE 100 or 102) of FIG. 1, 2 or 3, respectively. The source or target network device 104, 104a may be the same entity as the AN 104 or the satellite 106 of FIG. 1 , 2, or 3.

[0142] According to the one ofembodiments ofthe first aspect, the user device 100 can inform the network device 104 about its capability to keep track of DL synchronization of an activated TCI state through UE capability signalling.

[0143] At step S505, the source network device 104 may transmit a UE capability enquiry message to the user device.

[0144] At step S510, the user device 100 may inform the source network device 104 about its capability to keep track of DL synchronization of an activated TCI state through UE capability signalling. The capability may comprise the time duration explained in section 3.

[0145] S505 is optional, thus the user device 100 may transmit the UE capability information to the sourcenetwork device even though the UE capability enquiry message has not been received.

[0146] The capability of the user device 100 of S510 may be indicated at least in one of the following ways:- (1 ) The user device 100 may indicate the time duration. The time duration indicates time for which the user device is able to keep track of DL synchronization in time unit, such as milliseconds or slots. The time duration may have a set of alternative values such as, 320 ms, 480 ms, 1280 ms, or infinite (i.e. until cell switch or TCI state activation);- (2) the capability may indicate that the user device is able to keep track of DL synchronization without limitations or no support. In this case, the UE may indicate support of the capability if it does not have limitations on how long it can keep track of the DL synchronization of a TCI state after activation; or - (3) the capability may be indicated with respect to the measurement period of the reference signal (e.g., SSB or CSI-RS) associated to activated TCI state. For example, the user device is able to keep track of DL synchronization for X1 / X2 / .. ms when the SSB periodicity is Y1 / Y2 / .. ms. Alternatively, the user device may be able to keep track of DL synchronization for X3 (or X4) ms when the SSB periodicity is less than Y3 (or Y2) ms.

[0147] The capability may apply for all frequency ranges, or it may be applied and be informed separately for frequency range 1 (FR1) and FR2. The capability may be set per UE, per band or per BC.

[0148] The capability may have multiple components if different value applies for different frequency ranges.

[0149] The capability may be indicated via a DLsynchronizationDurationLTM IE. DLsynchronizationDurationLTM IE is one of examples of the time duration, and the components of the capabilities may be indicated as, for example:- DLsyncFRI = 160 ms, 320 ms, 480 ms or 1280 ms- DLsyncFR2 = 160 ms, 320 ms, 480 ms or 1280 ms

[0150] If the user device sets the values of the DLsynchronizationDurationLTM IE as the DLsyncFRI = 1280 ms and DLsyncFR2 = 160 ms, then the network may know that for FR1 when cell switch command is sent within 1280 ms, DL synchronization is valid and cell switch delay may be shorter. For FR2 cell switch command has to be sent within 160 ms for DL synchronization to be valid.

[0151] When the user device informs the DL synchronization duration (i.e., the time duration) through the UE capability information, the capability information may apply for all early LTM TCI state activations.

[0152] The embodiments of FIG. 5 may be applied to the LTM procedure explained in FIG. 2, and the embodiments of FIG. 4 may be applied to the embodiments of FIG. 5.

[0153] At step S515, referring to FIG. 5, the source network device 104 may transmit the TCI state activation command to the user device 100.

[0154] At step S520, the user device 100 may activate at least one TCI state according to the TCI state activation command. The at least one activated TCI state may be related to the source network device and / or the target network device.

[0155] At step S525, the user device 100 may keep track of DL synchronization with the activated TCI state related to the source and / or target network device 104, 104a during the time duration indicated by the capability information of S510.

[0156] If the UE autonomous TCI state activation is applied, the step S515 may not be performed. The user device 100 is able to activate the TCI state without the TCI state activation command (see section 2), and then the user device 100 may keep track of the DL synchronization based on the capability that has been indicated by the UE capability information.

[0157] FIG. 6 illustrates one of embodiments of the first aspect.

[0158] The network of FIG. 6 comprises the user device 100, the source network device 104, and the target network device 104a. The user device 100 may be the same entity as the UE (e.g., UE 100 or 102) of FIG. 1 , 2 or 3, respectively. The source or target network device 104, 104a may be the same entity as the AN 104 or the satellite 106 of FIG. 1 , 2 or 3.

[0159] For some user devices 100, 102, the UE capability to keep track of DL timing (e.g., synchronization) may depend on the number of cells and / or RSs the user device is measuring at the time of TCI state activation. This is because the user device may have the opportunity to maintain the DL synchronization less frequently, if the UE is measuring multiple candidate cells (measurement period is multiplied by the number of candidate cells in LTM).

[0160] Referring to FIG. 6, the methods of enabling more dynamic information sharing about the user device’s current capability to keep track of DL timing are disclosed.

[0161] At step S605, the source network device 104 transmits an LTM related message requesting the UE capability information. The LTM related message may be a TCI state activation command that is transmitted during the LTM executive process (e.g., S230). The LTM related message may be an RRC reconfiguration message that is transmitted during the LTM preparation process (e.g., S215).

[0162] At step S610, the user device 100 transmits the UE capability information to the source network device 104 in response to the LTM related message. The UE capability information indicates capability about the user device’s current capability to keep track of the DL timing. That is to say, the user device 100may indicate how long it is able to keep track of the DL synchronization.

[0163] When the user device 100 transmits the UE capability information, it may indicate the capability (i.e., the time duration) as separate values for each / set of the activated TCI states.

[0164] For example, when there are three TCI states A, B, and C. The user device 100 may inform that TCI state A will be tracked for Y ms and TCI states B and C will be tracked for Z ms and X ms, respectively. The TCI states may be indicated by corresponding TCI identifier.

[0165] Alternatively, the user device may give a tracking duration value (i.e., the time duration) for a subset of activated TCI states as:- Subset 1 : TCI state A, TCI state B: Y ms- Subset 2: TCI state C, TCI state D: Z ms

[0166] In another example, the UE may indicate a common value for a set of activated TCI states. For example, the capability may indicate that the DL sync will be tracked for all activated TCI states for X ms in common.

[0167] The signalling of S610 can be realized e.g., through MAC-CE. The user device 100 may signal to the network device 104 similar as in the static UE capability option:- (1) The user device 100 may indicate the time duration. The time duration indicates time for which the user device is able to keep track of DL synchronization in time units, such as milliseconds or slots. The time duration may have a set of alternative values such as, 320 ms, 480 ms, 1280 ms, or infinite (i.e. until cell switch or TCI state activation);- (2) the capability may indicate that the user device is able to keep track of DL synchronization without limitations. That is, the user device may indicate that it can keep track of the DL synchronization as long as needed; or- (3) the capability may be indicated with respect to the measurement period of the reference signal (e.g., SSB or CSI-RS) associated to activated TCI state. For example, the user device is able to keep track of DL synchronization for X1 / X2 / ... ms when the SSB periodicity is Y1 / Y2 / ... ms. Alternatively, the user device may be able to keep track of DL synchronization for X3 (or X4) ms when the SSB periodicity is less than Y3 (or Y2) ms.

[0168] In one example, the user device 100 may be configured (e.g., in the LTM configuration) to indicate UE capability about the UEs current capability to keep track of the DL timing dynamically (e.g., after receiving a TCI state activation command). This may be configured per candidate cell (e.g., it may be configured only for certain candidate cells) or per TCI state of different candidate cell (e.g., it may be configured for only for certain candidate TCI states for one or more candidate cell).

[0169] UE may indicate support of the dynamic UE capability indication as a UE capability in RRC.

[0170] If UE autonomous TCI state activation is considered, the user device 100 may send the dynamic capability information at the time of UE autonomous TCI state activation, In this case, the indication may be not a response to a TCI state activation command but to TCI state activation being triggered or completed.

[0171] 4.2 Embodiments of a second aspect of the disclosure

[0172] FIG. 7 illustrates embodiments of the second aspect of the disclosure.

[0173] The network environment comprises the user device 100 and the network device 104. The user device 100 may be the same entity as the UE (e.g., UE 100 or 102) of FIG. 1, 2 or 3, respectively. The network device 104 may be the same entity as the AN 104 or the satellite 106 of FIG. 1 , 2 or 3.

[0174] Regarding the user device 100, an apparatus for communication is to be explained. The apparatus may perform one of methods B1 -B5 and B12-B14, and the apparatus may be the user device 100 (e.g., UE). Alternatively or additionally, the apparatus may be embedded in the user device 100.

[0175] 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 to perform one of methods B1-B5 and B12-B14 shown by FIG. 7.

[0176] The apparatus may comprise one or more means for performing one of methods B1-B5 and B12-B14.

[0177] Referring to FIG. 7, the method B1 comprises steps S705 and S710.

[0178] At step S705, the apparatus 100 activates at least one transmission configuration indicator (TCI) state during a mobility procedure. The mobility procedure may be the LTM procedure (see, FIG. 2) comprising LTM execution process.

[0179] At step S710, the apparatus 100 transmits, to a network device 104, an indication indicative of stopping keeping track of at least one of synchronization related to the at least one activated TCI states.

[0180] As a method B2, the apparatus 100 is further caused to perform a step of transmitting, to the network device 104, capability information indicating that the apparatus supports a transmission of the indication.

[0181] As a method B3, the apparatus of B1 or B2 is further caused to perform a step of transmitting, to the network device 104, capability information indicative of an autonomous activation of the at least one TCI state. The at least one TCI state may have been autonomously activated by the apparatus.

[0182] As a method B4, the apparatus of any one of B1 to B3 is further caused to perform a step ofreceiving, from the network device 104, a message allowing the autonomous activation of the at least one TCI state. The message may further comprise information indicating a candidate cell where the autonomous TCI activation is performed. The message may be received before or after the capability information of B3. The message may be a LTM candidate cell RRC configuration message.

[0183] As a method B5, the apparatus of B1 or B2 is further caused to perform a step of receiving, from the network device 104, a TCI state activation command indicating to activate the at least one TCI state.

[0184] Regarding the network device 104, an apparatus for communication is to be explained. The apparatus may perform one of methods B6-B14, and the apparatus may be the network device 104. Alternatively or additionally, the apparatus may be embedded in the network device 104.

[0185] The apparatus 104 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 to perform one of methods B6-B14 shown by FIG. 7.

[0186] The apparatus 104 may comprise one or more means for performing one of methods B6-B14.

[0187] Referring to FIG. 7, the method B6 comprises step S710. The apparatus 104 receives, from a user device, an indication indicative of stopping keeping track of at least one of synchronization related to at least one TCI state.

[0188] As a method B7, the apparatus of B6 may be further caused to perform at least one of steps: transmitting an activation command to reactivate the at least one TCI state; or transmitting a cell switch command indicating to switch from a source cell to a candidate cell.

[0189] As a method B8, the apparatus of B6 or B7, may be further caused to perform a step of receiving, from the user device, capability information indicating that the apparatus supports a transmission of the indication.

[0190] As a method B9, the apparatus of any one of B6 to B8 may be further caused to perform: a step of receiving, from the user device, capability information indicative of an autonomous activation of TCI state. The at least one TCI state has been autonomously activated by the apparatus.

[0191] As a method B10, the apparatus of B9 may be further caused to perform a step of transmitting, to the user device, a message allowing the autonomous activation of the at least one TCI state.

[0192] As a method B11 , the apparatus of any one of B6 to B8 may be further caused to perform a step of transmitting a TCI state activation command indicating to activate the at least one TCI state.

[0193] As a method B12, the mobility procedure of any one of methods B1 to B11 is a low layer triggered mobility (LTM) procedure. The LTM procedure may be referred to FIG. 2.

[0194] As a method B13, the capability information of any one of B2 to B5 and B8 to B12 is determined based on at least one of a number of cells, a number of reference signal, or a frequency range at a time of the at least one activated TCI state has been activated.

[0195] As a method B14, the capability information any one of B2 to B5 and B8 to B13 is configured per at least one candidate cell or at least one TCI state of the at least one candidate cell.

[0196] One of examples of the second aspect, the procedure (or the method) of FIG. 7 may be performed by using a computer program. The computer program may comprise instructions, which, when executed by the apparatus (e.g., the user device 100 or the network device 104), cause the apparatus to perform the methods explained by FIG. 7.

[0197] One of examples of the first aspect, the computer-readable storage medium has stored thereon the computer program.

[0198] One of examples of the first aspect, a non-transitory computer readable medium has stored thereon the computer program.

[0199] FIG. 8 illustrates one of embodiments of the second aspect of the disclosure.

[0200] The network of FIG. 8 comprises the user device 100 and the network device 104. The user device 100 may be the same entity as the UE (e.g., UE 100 or 102) of FIG. 1, 2 or 3, respectively. The source or target network device 104, 104a may be the same entity as the AN 104 or the satellite 106 of FIG. 1 , 2, or 3.

[0201] Referring to FIG. 8, at step S805, the network device 104 may transmit the TCI state activation command to indicate activation of the at least one TCI state.

[0202] At step S810, the user device 100 activates the at least one TCI state. The activation may be performed according to the TCI state activation command. Alternatively, the activation may be performed autonomously by the user device 100 based on previous channel measurement.

[0203] At step S815, the user device 100 may keep track of at least one DL synchronization of the at least one of the activated TCI state.

[0204] At step S820, the user device 100 may send an indication to the network device 104 at the time when the user device stops keeping track of the DL synchronization of the at least one activated TCI state. Before receiving the indication, the network device 104 may assume that the user device 100 has a DL synchronization with an activated TCI state.

[0205] At step S825, the network device 104 may reactivate one or some of the at least one of the TCI state, or send a cell switch command to the user device. The network device 104 may expect a longer delaythan the delay time of the requirement explained in Table 1.

[0206] In some of embodiments of the second aspect, the user device 100 may transmit capability information comprising the time duration (see, section 3) to the network device 104. Alternatively, the user device 100 may do not transmit the capability information to the network device 104.

[0207] If the network sends a cell switch command before receiving such indication, the UE is required to perform the cell switch without DL synchronization. If the network receives such indication, and sends a cell switch command after that, the UE is allowed time for DL synchronization during the cell switch.

[0208] In one example of the second aspect, the user device may be configured (e.g., in the LTM configuration) to send an indication to the network device 104 at the time when the user device stops keeping track of the DL synchronization of an activated TCI state. This may be configured per candidate cell (e.g., it may be configured for only certain candidate cells) or per TCI state of different candidate cell (e.g., it may be configured for only certain candidate TCI states for one or more candidate cell).

[0209] This solution may be fairly unpredictable from the network point of view but provides a clear signal to the network about whether the UE has the DL synchronization or not. For example, if the network device 104 received the indication, the network device can assume that the early DL synchronization has not been maintained and also assume that the user device will perform DL synchronization during the cell switch procedure.

[0210] In one of embodiments of the second aspect, the user device 100 may indicate the support of the dynamic UE indication via the UE capability information in RRC.

[0211] In one of embodiments of the second aspect, the UE autonomous TCI state activation may be considered. The second aspect of the disclosure may depend on whether there is some signalling related to the UE autonomous TCI state activation. The user device 100 may send the indication about stopping to keep track of the fine DL synchronization here as in the command-based option.

[0212] However, whether the network device has been aware of the user device 100 having activated a TCI state depends on how UE autonomous TCI state activation is realized. For the purposes of this invention, the signal can be generally sent after the user device has autonomously activated a TCI state and when the user device 100 stops keeping track of the DL synchronization of this TCI state.

[0213] 4.3 Embodiments of a third aspect of the disclosure

[0214] FIG. 9 illustrates embodiments of the first aspect of the disclosure.

[0215] The network environment comprises the user device 100 and the network device 104. The user device 100 may be the same entity as the UE (e.g., UE 100 or 102) of FIG. 1, 2 or 3, respectively. Thenetwork device 104 may be the same entity as the AN 104 or the satellite 106 of FIG. 1 , 2 or 3.

[0216] Regarding the user device 100, an apparatus for communication is to be explained. The apparatus may perform one of methods C1-C8 and C14-C18, and the apparatus may be the user device 100. Alternatively or additionally, the apparatus may be embedded in the user device 100.

[0217] The apparatus 100 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 to perform one of methods C1-C8 and C14-C18 shown by FIG. 9.

[0218] The apparatus 100 may comprise one or more means for performing one of methods C1-C8 and C14-C18.

[0219] Referring to FIG. 9, the method C1 comprises steps S905, S910, and S915.

[0220] At step S905, the apparatus 100 receives, from the network device 104, an indication indicative of time duration to keep track of at least one synchronization related to at least one transmission configuration indicator (TCI) state.

[0221] At step S910, the apparatus 100 activates the at least one TCI state during a mobility procedure. The mobility procedure may be the LTM procedure (see, FIG. 2) comprising LTM execution process.

[0222] At step S915, the apparatus 100 keeps track of the at least one synchronization related to the at least one TCI state based on the time duration. For example, the apparatus 100 may keep track of the at least one downlink synchronization related to the at least one activated TCI state according to the time duration (see, section 3) has been indicated.

[0223] As a method C2, the apparatus of C1 may be further caused to perform a step of transmitting, to the network device 104, capability information related to a low layer triggered mobility (LTM) procedure. The capability information may indicate that the apparatus 100 is able to keep track of at least one of synchronization related to the at least one activated TCI state.

[0224] As a method C3, the capability information of C2 may comprise time period information that is supported by the apparatus.

[0225] As a method C4, the time duration of C3 may be determined based on the time period information.

[0226] As a method C5, the indication of any one of C1 to C4 may be received via one of:- a TCI state activation command indicating to activate the at least one TCI state,- a medium access control control element, MAC CE,- a candidate cell configuration message, and- a RRC reconfiguration message.

[0227] As a method C6, the apparatus of any one of C1 to C5 may be further caused to perform a step of transmitting, to the network device 104, capability information indicative of an autonomous activation of the at least one TCI state. This capability information may be the same as the capability info of C2 or not.

[0228] As a method C7, the at least one TCI state of any one of C1 to C6 may be autonomously activated based on the capability information indicative of the autonomous activation of the at least one TCI state.

[0229] As a method C8, the apparatus of C6 or C7 may be further caused to perform step of receiving, from the network device 104, a message allowing the autonomous activation of the at least one TCI state.

[0230] The message may further comprise information indicating a candidate cell where the autonomous TCI activation is performed. The message may be received before or after the capability information of B3. The message may be an LTM candidate cell RRC configuration message.

[0231] Regarding the network device 104, an apparatus for communication is to be explained. The apparatus may perform one of methods C9-C18, and the apparatus may be the network device 104. Alternatively or additionally, the apparatus may be embedded in the network device 104.

[0232] The apparatus 104 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 to perform one of methods C9-C18 shown by FIG. 9.

[0233] The apparatus 104 may comprise one or more means for performing one of methods C9-C18.

[0234] Referring to FIG. 9, the method C9 comprises step S905.

[0235] At step S905, the apparatus 104 transmits, to a user device 100, an indication indicative of time duration to keep track of at least one synchronization related to at least one transmission configuration indicator (TCI) state.

[0236] As a method C10, the apparatus of C9 may be further caused to perform a step of receiving, from the user device 100, capability information related to a low layer triggered mobility (LTM) procedure. The capability information may indicate that the user device 100 is able to keep track of at least one of synchronizations related to the at least one activated TCI state.

[0237] As a method C11, the capability information of C10 may comprise time period information that is supported by the user device.

[0238] As a method C12, the time duration of C11 may be determined based on the time period information.

[0239] As a method C13, the indication of any one of C9 to C12 may be transmitted via one of:- a TCI state activation command (indicating to activate the at least one TCI state),- a medium access control control element, MAC CE,- a candidate cell configuration message, and- a RRC reconfiguration message.

[0240] As a method C14, the apparatus 104 of any one of C9 to C13 may be further caused to perform a step of receiving, from the user device 100, capability information indicative of an autonomous activation of the at least one TCI state.

[0241] As a method C15, the apparatus of C14 may be further caused to perform a step of transmitting, to the user device 100, a message allowing the autonomous activation of the at least one TCI state.

[0242] As a method C16, the mobility procedure of any one of C1 to C15 may be a low layer triggered mobility (LTM) procedure.

[0243] As a method C17, the capability information any one of C2 to C8 and C10 to C16 may be determined based on at least one of a number of cells, a number of reference signal, or a frequency range at a time of the at least one activated TCI state has been activated.

[0244] As a method C18, the capability information of any one of C2 to C8 and C10 to C17 may be configured per at least one candidate cell or at least one TCI state of the at least one candidate cell.

[0245] One of examples of the second aspect, the procedure (or the method) of FIG. 9 may be performed by using a computer program. The computer program may comprise instructions, which, when executed by the apparatus (e.g., the user device 100 or the network device 104), cause the apparatus to perform the methods explained by FIG. 9.

[0246] One of examples of the first aspect, the computer-readable storage medium has stored thereon the computer program.

[0247] One of examples of the first aspect, a non-transitory computer readable medium has stored thereon the computer program.

[0248] FIG. 10 illustrates one of embodiments of the third aspect of the disclosure.

[0249] The network of FIG. 10 comprises the user device 100 and the network device 104. The user device 100 may be the same entity as the UE (e.g., UE 100 or 102) of FIG. 1, 2 or 3, respectively. The network device 104 may be the same entity as the AN 104 or the satellite 106 of FIG. 1 , 2, or 3.

[0250] Referring to Fig. 10, at step S1010, the network device may transmit an indication indicative of a time duration (Tmamtam). For example, the network device 104 may specifically indicate to the user device 100 that the user device shall keep track of the DL synchronization of an activated TCI state for a configured time period (Tmamtam). The network device 104 may transmit the indication via an RRC configuration (e.g.LTM configuration) message indicating that the user device 100 shall keep track of the DL synchronization for X ms, based on TCI state activation.

[0251] The X ms may be indicated as an absolute value, or it may be indicated as a value from a set of values such as 320 ms, 480 ms, or 1280 ms etc.

[0252] In one of embodiments of the third aspect, the indication of S1010 may be transmitted via an RRC message. In this case, the indication may be applied to all TCI state activations after that. The indication may also be frequency range specific (separate for FR1 and FR2) or candidate cell specific (separate value for different candidate cells).

[0253] In one of embodiments of the third aspect, the indication of S1010 may be transmitted via a MAC CE. For example, the network device may transmit the indication dynamically at the time of TCI state activation (e.g., via the TCI state activation command). In this case the indication applies only to the TCI states that are activated.

[0254] Referring to FIG. 10, at step 1015, the user device 100 may activate the TCI state. The activation can be performed according to an indication from the network device 104. The activation can be performed autonomously by the user device 100.

[0255] At step S1020, the user device 100 may keep track of synchronization according to the indication of S1010.

[0256] At step S1005, the user device 100 may indicate support of network indication about keeping track of the DL synchronization based on network indication as a UE capability in RRC. The capability may include a maximum value for UE being able to keep track of DL synchronization of the TCI state and the network may indicate a value that is up to this capability. Step 1005 is optional, thus it may not be performed.

[0257] FIG. 11 illustrates an example of an apparatus 1100 comprising means for performing one or more of the example embodiments described above. For example, the apparatus 1100 may be, or comprise, or be comprised in, the user device 100. The apparatus 1100 may perform any operations disclosed in FIG. 1 to 10.

[0258] The apparatus 1100 may comprise a circuitry or a chipset applicable for realizing one or more of the example embodiments described above. For example, the apparatus 1100 may comprise at least one processor 1110. The at least one processor 1110 interprets instructions (e.g., computer program instructions) and processes data. The at least one processor 1110 may comprise one or more programmable processors. The at least one processor 1110 may comprise programmable hardware with embedded firmware and may, alternatively or additionally, comprise one or more application-specific integrated circuits (ASICs).

[0259] The at least one processor 1110 is coupled to at least one memory 1120. The at least one processor is configured to read and write data to and from the at least one memory 1120. The at least one memory 1120 may comprise one or more memory units. The memory units may be volatile or non-volatile. It is to be noted that there may be one or more units of non-volatile memory and one or more units of volatile memory or, alternatively, one or more units of non-volatile memory, or, alternatively, one or more units of volatile memory. Volatile memory may be for example random-access memory (RAM), dynamic random-access memory (DRAM) or synchronous dynamic random-access memory (SDRAM). Non-volatile memory may be for example read-only memory (ROM), programmable read-only memory (PROM), electronically erasable programmable read-only memory (EEPROM), flash memory, optical storage or magnetic storage. In general, memories may be referred to as non-transitory computer readable media. The 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., RAM vs. ROM). The at least one memory 1120 stores computer readable instructions that are executed by the at least one processor 1110 to perform one or more of the example embodiments described above. For example, non-volatile memory stores the computer readable instructions, and the at least one processor 1110 executes the instructions using volatile memory for temporary storage of data and / or instructions. The computer readable instructions may refer to computer program code.

[0260] The computer readable instructions may have been pre-stored to the at least one memory 1120 or, alternatively or additionally, they may be received, by the apparatus, via an electromagnetic carrier signal and / or may be copied from a physical entity such as a computer program product. Execution of the computer readable instructions by the at least one processor 1110 causes the apparatus 1100 to perform one or more of the example embodiments described above. That is, the at least one processor and the at least one memory storing the instructions may provide the means for providing or causing the performance of any of the methods and / or blocks described above.

[0261] In the context of this document, a “memory” or “computer-readable media” or “computer-readable medium” may be any non-transitory media or medium or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. The 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., RAM vs. ROM).

[0262] The apparatus 1100 may further comprise, or be connected to, an input unit 1130. The input unit 1130 may comprise one or more interfaces for receiving input. The one or more interfaces may comprise for example one or more temperature, motion and / or orientation sensors, one or more cameras, one or more accelerometers, one or more microphones, one or more buttons and / or one or more touch detection units. Further, the input unit 1130 may comprise an interface to which external devices may connect to.

[0263] The apparatus 1100 may also comprise an output unit 1140. The output unit may comprise or be connected to one or more displays capable of rendering visual content, such as a light emitting diode (LED) display, a liquid crystal display (LCD) and / or a liquid crystal on silicon (LCoS) display. The output unit 1140 may further comprise one or more audio outputs. The one or more audio outputs may be for example loudspeakers.

[0264] The apparatus 1100 further comprises a connectivity unit 1150. The connectivity unit 1150 enables wireless connectivity to one or more external devices. The connectivity unit 1150 comprises at least one transmitter and at least one receiver that may be integrated to the apparatus 1100 or that the apparatus 1100 may be connected to. The at least one transmitter comprises at least one transmission antenna, and the at least one receiver comprises at least one receiving antenna. The connectivity unit 1150 may comprise an integrated circuit or a set of integrated circuits that provide the wireless communication capability for the apparatus 1100. Alternatively, the wireless connectivity may be a hardwired application-specific integrated circuit (ASIC). The connectivity unit 1150 may also provide means for performing at least some of the blocks or functions of one or more example embodiments described above. The connectivity unit 1150 may comprise one or more components, such as: power amplifier, digital front end (DFE), analog-to-digital converter (ADC), digital-to-analog converter (DAC), frequency converter, (de)modulator, and / or encoder / decoder circuitries, controlled by the corresponding controlling units.

[0265] It is to be noted that the apparatus 1100 may further comprise various components not illustrated in FIG. 11. The various components may be hardware components and / or software components.

[0266] The apparatus 1100 may perform or be applied with the embodiments described above. More specifically, the apparatus 1100 may be the user device 100, and the user device 100 may be configured to perform one of the methods explained by using FIGs. 1 to 5.

[0267] FIG. 12 illustrates an example of an apparatus 1200 comprising means for performing one or more of the example embodiments described above. For example, the apparatus 1200 may be an apparatus such as, or comprising, or comprised in, the network device 104 or the network entity, and support the embodiments and examples described above.

[0268] The network device 104 may also be referred to, for example, as a network element, a next generation radio access network (NG-RAN) node, a NodeB, an eNB, a gNB, a base transceiver station (BTS), a base station, an NR base station, a 5G base station, an access node, an access point (AP), a cell site, a relay node, a repeater, an integrated access and backhaul (IAB) node, an IAB donor node, a distributed unit (DU), a central unit (CU), a baseband unit (BBU), a radio unit (RU), a radio head, a remote radio head (RRH), or a transmission and reception point (TRP).

[0269] The apparatus 1200 may comprise, for example, a circuitry or a chipset applicable for realizing one or more of the example embodiments described above. The apparatus 1200 may be an electronic device comprising one or more electronic circuitries. The apparatus 1200 may comprise a communication control circuitry 1210 such as at least one processor, and at least one memory 1220 storing instructions 1222 which, when executed by the at least one processor, cause the apparatus 1200 to carry out one or more of the example embodiments described above. Such instructions 1222 may, for example, include computer program code (software). The at least one processor and the at least one memory storing the instructions may provide the means for providing or causing the performance of any of the methods and / or blocks described above.

[0270] The processor is coupled to the memory 1220. The processor is configured to read and write data to and from the memory 1220. The memory 1220 may comprise one or more memory units. The memory units may be volatile or non-volatile. It is to be noted that there may be one or more units of non-volatile memory and one or more units of volatile memory or, alternatively, one or more units of non-volatile memory, or, alternatively, one or more units of volatile memory. Volatile memory may be for example random-access memory (RAM), dynamic random-access memory (DRAM) or synchronous dynamic random-access memory (SDRAM). Non-volatile memory may be for example read-only memory (ROM), programmable read-only memory (PROM), electronically erasable programmable read-only memory (EEPROM), flash memory, optical storage or magnetic storage. In general, memories may be referred to as non-transitory computer readable media. The 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., RAM vs. ROM). The memory 1220 stores computer readable instructions that are executed by the processor. For example, non-volatile memory stores the computer readable instructions, and the processor executes the instructions using volatile memory for temporary storage of data and / or instructions.

[0271] The computer readable instructions may have been pre-stored to the memory 1220 or, alternatively or additionally, they may be received, by the apparatus, via an electromagnetic carrier signal and / or may be copied from a physical entity such as a computer program product. Execution of the computer readable instructions causes the apparatus 1200 to perform one or more of the functionalities described above.

[0272] The memory 1220 may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and / or removable memory. The memory may comprise a configuration database for storing configuration data, such as a current neighbour cell list, and, in some example embodiments, structures of frames used in the detected neighbour cells.

[0273] The apparatus 1200 may further comprise or be connected to a communication interface 1230,such as a radio unit, comprising hardware and / or software for realizing communication connectivity with one or more wireless communication devices according to one or more communication protocols. The communication interface 1230 comprises at least one transmitter (Tx) and at least one receiver (Rx) that may be integrated to the apparatus 1200 or that the apparatus 1200 may be connected to. The communication interface 1230 may provide means for performing some of the blocks for one or more example embodiments described above. The communication interface 1230 may comprise one or more components, such as: power amplifier, digital front end (DFE), analog-to-digital converter (ADC), digital-to-analog converter (DAC), frequency converter, (de)modulator, and / or encoder / decoder circuitries, controlled by the corresponding controlling units.

[0274] The communication interface 1230 provides the apparatus with radio communication capabilities to communicate in the wireless communication network. The communication interface may, for example, provide a radio interface to one or more wireless communication devices. The apparatus 1200 may further comprise or be connected to another interface towards a core network such as the network coordinator apparatus or AMF, and / or to the access nodes of the wireless communication network.

[0275] The apparatus 1200 may further comprise a scheduler 1240 that is configured to allocate radio resources. The scheduler 1240 may be configured along with the communication control circuitry 1210 or it may be separately configured.

[0276] It is to be noted that the apparatus 1200 may further comprise various components not illustrated in FIG. 12. The various components may be hardware components and / or software components.

[0277] The apparatus 1200 may perform or be applied with the embodiments described above. More specifically, the apparatus 1200 may be the network device 104, and the network device 104 may be configured to perform one of the methods explained by using FIGs. 1 to 5.

[0278] The techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. For a hardware implementation, the apparatus(es) of example embodiments may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), graphics processing units (GPUs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. For firmware or software, the implementation can be carried out through modules of at least one chipset (for example procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit and executed by processors. The memory unit may be implemented within the processor or externally to theprocessor. In the latter case, it can be communicatively coupled to the processor via various means, as is known in the art. Additionally, the components of the systems described herein may be rearranged and / or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

[0279] It will be obvious to a person skilled in the art that, as technology advances, the inventive concept may be implemented in various ways. The embodiments are not limited to the example embodiments described above, but may vary within the scope of the claims. Therefore, all words and expressions should be interpreted broadly, and they are intended to illustrate, not to restrict, the embodiments.

Claims

37WHAT IS CLAIMED IS:

1. 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 perform:receiving, from a network device, an indication indicative of time duration to keep track of at least one synchronization related to at least one transmission configuration indicator, TCI, state;activating the at least one TCI state during a mobility procedure; andkeeping track of the at least one synchronization related to the at least one TCI state based on the time duration.

2. The apparatus of claim 1 , wherein the apparatus is further caused to perform:transmitting, to the network device, capability information related to a low layer triggered mobility, LTM, procedure, the capability information indicating that the apparatus is able to keep track of at least one of synchronization related to the at least one activated TCI state.

3. The apparatus of claim 2, wherein the capability information comprises time period information that is supported by the apparatus.

4. The apparatus of claim 3, wherein the time duration is determined based on the time period information.

5. The apparatus of claim any one of claims 1 to 4, wherein the indication is received via one of: a TCI state activation command (indicating to activate the at least one TCI state),a medium access control control element, MAC CE,a candidate cell configuration message, andan RRC reconfiguration message.

6. The apparatus of any one of claims 1 to 5, wherein the apparatus is further caused to perform:transmitting, to the network device, capability information indicative of an autonomous activation of the at least one TCI state.

7. The apparatus of any one of claims 1 to 6, wherein the at least one TCI state is autonomously activated based on the capability information indicative of the autonomous activation of the at least one TCI state.

8. The apparatus of claim 6 or 7, wherein the apparatus is further caused to perform:receiving, from the network device, a message allowing the autonomous activation of the at least one TCI state.

9. 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 perform:transmitting, to a user device, an indication indicative of time duration to keep track of at least one synchronization related to at least one transmission configuration indicator, TCI, state.

10. The apparatus of claim 9, wherein the apparatus is further caused to perform:receiving, from the user device, capability information related to a low layer triggered mobility, LTM, procedure, the capability information indicating that the user device is able to keep track of at least one of synchronization related to the at least one activated TCI state.

11. The apparatus of claim 10, wherein the capability information comprises time period information that is supported by the user device.

12. The apparatus of claim 11, wherein the time duration is determined based on the time period information.

13. The apparatus of claim any one of claims 9 to 12, wherein the indication is transmitted via one of:a TCI state activation command (indicating to activate the at least one TCI state),a medium access control control element, MAC CE,a candidate cell configuration message, andan RRC reconfiguration message.

14. The apparatus of any one of claims 9 to 13, wherein the apparatus is further caused to perform: receiving, from the user device, capability information indicative of an autonomous activation of the at least one TCI state.

15. The apparatus of claim 14, wherein the apparatus is further caused to perform: transmitting, to the user device, a message allowing the autonomous activation of the at least one TCI state.

16. The apparatus of any one of claims 1 to 15, wherein the mobility procedure is a low layer triggered mobility, LTM, procedure.

17. The apparatus of any one of claims 2 to 8 and 10 to 16, wherein the capability information is determined based on at least one of a number of cells, a number of reference signal, or a frequency range at a time of the at least one activated TCI state has been activated.

18. The apparatus of any one of claims 2 to 8 and 10 to 17, wherein the capability information is configured per at least one candidate cell or at least one TCI state of the at least one candidate cell.

19. A method comprising:receiving, from a network device, an indication indicative of time duration to keep track of at least one synchronization related to at least one transmission configuration indicator, TCI, state;activating the at least one TCI state during a mobility procedure; andkeeping track of the at least one synchronization related to the at least one TCI state based on the time duration.

20. A method comprising:transmitting, to a user device, an indication indicative of time duration to keep track of at least one synchronization related to at least one transmission configuration indicator, TCI, state.

21. A computer program comprising instructions, which, when executed by an apparatus, cause the apparatus to perform the method of any one of claims 19 to 20.

22. A computer-readable storage medium having stored thereon the computer program of claim 21.

23. A non-transitory computer readable medium having stored thereon the computer program of claim 21.

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