Wireless communications device, network node and methods

Abstract

Disclosed is a wireless communication device, network node and methods arranged to provide handover mobility decisions based on the measurement report of neighboring cells received from the user equipment. Disclosed is a wireless communication deployment scenario, in which a candidate timing advance group configuration is utilized, the configuration comprising an identification and a mapping of an associated timing advance group.

Description

[0001] DESCRIPTION

[0002] TITLE WIRELESS COMMUNICATIONS DEVICE, NETWORK NODE AND METHODS TECHNICAL FIELD

[0003] The following example embodiments relate to information technology and to wireless communication.

[0004] BACKGROUND

[0005] Information technology has an ever-growing impact on our society. In wireless communications networks, such as in 5G networks, during the mobility a small interruption time for user equipment is important for providing reliable communication. Present cellular network technologies allow handover mobility decisions based on the measurement report of neighboring cells received from the user equipment.

[0006] SUMMARY

[0007] The scope of protection sought for various example embodiments is set out by the 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.

[0008] According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.

[0009] According to an aspect, there is provided a device comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the device at least to: receive, over a wireless network connection, at least a first candidate configuration and a second candidate configuration for a conditional layer 1 / layer 2 triggered mobility, LTM, cell switch; receive, over the wireless connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group, TAG, associated with a serving cell or a candidate cell of a cellswitch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification, and wherein a TAG of a candidate cell of the first candidate configuration is mapped to the same CTAG configuration as a TAG of a serving cell or a TAG of a candidate cell of the second candidate configuration; start, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; and based on detecting that a condition for a cell switch to the candidate cell of the first candidate configuration is met, use the received TA value for the candidate cell of the first candidate configuration by using the CTAG configuration and perform the cell switch to the candidate cell of the first candidate configuration without random access.

[0010] According to an embodiment, the first candidate configuration, the second candidate configuration, the CTAG configuration, and conditions for triggering the conditional LTM cell switch are received via radio resource control signalling.

[0011] According to an embodiment, the mapping is formed by an identifier of the timing advance group associated with the serving cell or a candidate cell of a cell switch, wherein the identifier is received in connection with the CTAG identification.

[0012] According to an embodiment, the device is configured to determine, when the cell switch is to be performed to a candidate cell, the TA value to be used to access the candidate cell to be equal to the TA value associated with the CTAG to which the TAG of the candidate cell has been mapped.

[0013] According to an embodiment, the timing advance group of the candidate cell of the first configuration is a primary timing advance group or a secondary timing advance group.

[0014] According to an embodiment, the CTAG configuration is mapped to a primary TAG of a serving cell.

[0015] According to an embodiment, the CTAG configuration is mapped to a secondary TAG of a serving cell.According to an embodiment, no TAT is configured for the CTAG configuration.

[0016] According to an embodiment, the CTAG configuration is mapped to a TAG that contains no serving cells.

[0017] According to an embodiment, the device comprises or is comprised in a user equipment.

[0018] According to an aspect, there is provided method, comprising: comprising: receiving, over a wireless network connection, at least a first candidate configuration and a second candidate configuration for a conditional layer 1 / layer 2 triggered mobility, LTM, cell switch; receiving, over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group, TAG, associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification, and wherein a TAG of a candidate cell of the first candidate configuration is mapped to the same CTAG configuration as a TAG of a serving cell or a TAG of a candidate cell of the second candidate configuration; starting, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; and based on detecting that a condition for a cell switch to the candidate cell of the first candidate configuration is met, using the received TA value for the candidate cell of the first candidate configuration by using the CTAG configuration and performing the cell switch to the candidate cell of the first candidate configuration without random access.

[0019] According to an embodiment, the first candidate configuration, the second candidate configuration, the CTAG configuration, and conditions for triggering the conditional LTM cell switch are received via radio resource control signalling.

[0020] According to an embodiment, the mapping is formed by an identifier of the timing advance group associated with the serving cell or a candidate cell of acell switch, wherein the identifier is received in connection with the CTAG identification.

[0021] According to an embodiment, when the cell switch is to be performed to a candidate cell, the TA value to be used to access the candidate cell is determined to be equal to the TA value associated with the CTAG to which the TAG of the candidate cell has been mapped.

[0022] According to an embodiment, the timing advance group of the candidate cell of the first configuration is a primary timing advance group or a secondary timing advance group.

[0023] According to an embodiment, the CTAG configuration is mapped to a primary TAG of a serving cell.

[0024] According to an embodiment, the CTAG configuration is mapped to a secondary TAG of a serving cell.

[0025] According to an embodiment, no TAT is configured for the CTAG configuration.

[0026] According to an embodiment, the CTAG configuration is mapped to a TAG that contains no serving cells.

[0027] According to an embodiment, the method is carried out in a user equipment.

[0028] According to an aspect, there is provided a device comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the device at least to: receive, over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; start, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; and when a cell switch is to be performed to a candidate cell of the CTAG identification and the TAT associated with the CTAG identification is running, perform the cell switch without random access.According to an embodiment, said mapping comprises multiple CTAG configurations for the mapped candidate cells, wherein the CTAG configurations are associated with differing TA values.

[0029] According to an embodiment, the time alignment timer is common to the multiple CTAG configurations.

[0030] According to an embodiment, the at least one CTAG configuration is associated with a primary cell and a secondary cell.

[0031] According to an embodiment, the CTAG configuration comprises a TAT value common to the candidate cells mapped to the same CTAG identification.

[0032] According to an embodiment, the device is configured to receive the TA value together with a CTAG identification in a medium access control, MAC, control element.

[0033] According to an embodiment, the device is configured to determine, when the cell switch is to be performed to a candidate cell for which no TA value has been received in a cell switch command, a TA value for the candidate cell from that CTAG configuration to which the candidate cell has been mapped.

[0034] According to an embodiment, the device comprises or is comprised in a user equipment.

[0035] According to an aspect, there is provided a network node comprising: at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the network node at least to: obtain at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; and transmit, over a wireless network connection, at least one CTAG configuration to user equipment for cell switch of the user equipment.

[0036] According to an embodiment, said network node obtains at least one CTAG configuration based on received user equipment measurement reports.

[0037] According to an embodiment, said network node obtains at least one CTAG configuration from a candidate central unit of the cell switch.According to an embodiment, said network node receives, from the candidate central unit of the cell switch a set of mappings, each mapping comprising for a candidate cell an index of a configured primary or secondary timing advance group and a value indicating a CTAG of the candidate cell.

[0038] According to an embodiment, said network node is configured to send timing advance, TA, values for the CTAG identification for one or more associated CTAGs to the user equipment.

[0039] According to an embodiment, said mapping comprises several CTAG configurations for the mapped candidate cells wherein one or more of said mapped candidate cells are mapped more than once to either a primary timing advance group or a secondary timing advance group of different CTAG configurations.

[0040] According to an embodiment, said CTAG identification is associated with a primary cell and a secondary cell.

[0041] According to an embodiment, the CTAG configuration comprises a TAT value common to the candidate cells mapped to the same CTAG identification.

[0042] According to an aspect, there is provided method, comprising: receiving, over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; starting, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; and when a cell switch is to be performed to a candidate cell of the CTAG identification and the TAT associated with the CTAG identification is running, performing the cell switch without random access.

[0043] According to an embodiment, said mapping comprises multiple CTAG configurations for the mapped candidate cells, wherein the CTAG configurations are associated with differing TA values.

[0044] According to an embodiment, the at least one CTAG configuration is associated with a primary cell and a secondary cell.According to an embodiment, the CTAG configuration comprises a TAT value common to the candidate cells mapped to the same CTAG identification.

[0045] According to an aspect, there is provided method, comprising: obtaining at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; and transmitting, over a wireless network connection, at least one CTAG configuration to user equipment for cell switch of the user equipment.

[0046] According to an embodiment, said mapping comprises multiple CTAG configurations for the mapped candidate cells, wherein the CTAG configurations are associated with differing TA values.

[0047] According to an embodiment, the at least one CTAG configuration is associated with a primary cell and a secondary cell.

[0048] According to an embodiment, the CTAG configuration comprises a TAT value common to the candidate cells mapped to the same CTAG identification.

[0049] According to an aspect, there is provided computer readable medium comprising program instructions which, when executed by a device, cause the device to perform at least the following: receive, over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; start, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; and when a cell switch is to be performed to a candidate cell of the CTAG identification and the TAT associated with the CTAG identification is running, performing the cell switch without random access.

[0050] According to an embodiment, said the computer readable medium is a non-transitory computer readable medium.According to an aspect, there is provided computer program comprising instructions for causing a device to perform at least the method, comprising: receiving, over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; starting, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; and when a cell switch is to be performed to a candidate cell of the CTAG identification and the TAT associated with the CTAG identification is running, performing the cell switch without random access.

[0051] According to an aspect, there is provided device comprising at least means for performing the method, comprising: receiving, over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; starting, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; and when a cell switch is to be performed to a candidate cell of the CTAG identification and the TAT associated with the CTAG identification is running, performing the cell switch without random access.

[0052] According to an aspect, there is provided a computer readable medium comprising program instructions which, when executed by a network node, cause the network node to perform at least the following: obtain at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; and transmit, over a wireless network connection, at least one CTAG configuration to user equipment for cell switch of the user equipment.According to an embodiment, said the computer readable medium is a non-transitory computer readable medium.

[0053] According to an aspect, there is provided computer program comprising instructions for causing a network node to perform at least the method, comprising: obtaining at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; and transmitting, over a wireless network connection, at least one CTAG configuration to user equipment for cell switch of the user equipment.

[0054] According to an aspect, there is provided device comprising at least means for performing the method, comprising: obtaining at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification; and transmitting, over a wireless network connection, at least one CTAG configuration to user equipment for cell switch of the user equipment.

[0055] BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In the following, various example embodiments will be described in greater detail with reference to the accompanying drawings, in which

[0057] FIG. 1 illustrates an example of a wireless communication network; FIG. 2 shows an example embodiment of a wireless communication deployment scenario;

[0058] FIG. 3 illustrates a schematic representation of an example configuration of a wireless communication deployment scenario;

[0059] FIG. 4 illustrates a schematic representation of an example configuration of a wireless communication deployment scenario utilising candidate TAGs;

[0060] FIG. 5 illustrates an example embodiment of a flow diagram of awireless communication deployment scenario utilising candidate TAGs;

[0061] FIG. 6 illustrates another example embodiment of a flow diagram of a wireless communication deployment scenario utilising candidate TAGs;

[0062] FIG. 7 illustrates a third example embodiment of a flow diagram of a wireless communication deployment scenario utilising candidate TAGs;

[0063] FIG. 8 illustrates an example embodiment of a message sequence chart of a wireless communication deployment scenario utilising candidate TAGs;

[0064] FIG. 9 illustrates an example of an apparatus comprising means for performing one or more of the example embodiments described above;

[0065] FIG. 10 illustrates an example of an apparatus comprising means for performing one or more of the example embodiments described above;

[0066] FIG. 11 illustrates an example of an apparatus according to some embodiments of the present invention in connection with the user equipment;

[0067] FIG. 12 illustrates an example of an apparatus according to some embodiments of the present invention in connection with the network node.

[0068] DETAILED DESCRIPTION

[0069] The following embodiments are exemplifying. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments within the scope of the claims. Furthermore, the words "comprising" and "including" should be understood as not limiting the described embodiments to consist of only those features that have been mentioned, and such embodiments may also contain features that have not been specifically mentioned. Reference numbers, in the description and / or in the claims, serve to illustrate the embodiments with reference to the drawings, without limiting the embodiments to these examples only.

[0070] Further, it should be appreciated that, as used herein, the terms “the at least one” and “the one or more” mean “any one of the at least one” and “any one ofthe one or more”, respectively. Furthermore, 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.

[0071] Some example embodiments described herein may be implemented in a wireless communication network comprising a radio access network based on one or more of the following radio access technologies (RATs): long term evolution (LTE), LTE-Advanced, fourth generation (4G), fifth generation (5G ), 5G new radio (NR), 5G-Advanced (i.e., 3GPP NR Rel-18 and beyond), sixth generation (6G), or seventh generation (7G). Some examples of radio access networks include the universal mobile telecommunications system (UMTS) radio access network (UTRAN), the evolved universal terrestrial radio access network (E-UTRA), or the next generation radio access network (NG-RAN). The wireless communication network may further comprise a core network, and some example embodiments may also be applied to network functions of the core network.

[0072] FIG. 1 depicts an example of a simplified wireless communication network showing some physical and logical entities. The connections shown in FIG.

[0073] 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.

[0074] 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 example embodiments described herein to other wireless communication networks provided with necessary properties.

[0075] The example wireless communication network shown in FIG. 1 includes a radio access network (RAN) and a core network 110.

[0076] 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 104 of a radio access network.The access node 104 may comprise a computing device configured to control the radio resources of the access node 104 and to be in a wireless connection with one or more UEs 100, 102. The access node 104 may also be referred to as a base station, a base transceiver station (BTS), an access point, a cell site, a network node, a radio access network node, a RAN node, or a network device.

[0077] The access node 104 may be, for example, 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 gNB or gNodeB), providing the radio cell. The access node 104 may include or be coupled to transceivers. From the transceivers of the access node 104, a connection may be provided to an antenna unit that establishes a bi-directional radio link to one or more UEs 100, 102. The antenna unit may comprise an antenna or antenna element, or a plurality of antennas or antenna elements.

[0078] The wireless connection (e.g., radio link) from a UE 100, 102 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 104 to the UE 100, 102 may be called downlink (DL) or forward link. A UE 100 may also communicate directly with another 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, access point or other entity suitable for providing such functionalities.

[0079] The radio access network may comprise more than one access node 104, in which case the access nodes may also be configured to communicate with one another over wired or wireless links. These links between access nodes may be used for sending and / or receiving control plane signaling and also for routing data from one access node to another access node.

[0080] 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 5thgeneration 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 toexternal packet data networks, and / or a mobility management entity (MME). The 5GC may comprise one or more network functions, such as at least one of: a user plane function (UPF), an access and mobility management function (AMF), a location management function (LMF), and / or a session management function (SMF).

[0081] 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.

[0082] 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, or even be nonexistent.

[0083] 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 100, 102 may be a computing device operating with or without 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 household appliance with radio parts, a sensor comprising a wireless modem, or a computing device comprising a wireless modem integrated in a vehicle or in a house.It should be appreciated that the UE 100, 102 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. The UE 100, 102 may also be a device having capability to operate in an Internet of Things (IoT) 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.

[0084] The wireless communication network may also comprise a central control entity, such as a network management system (NMS), or the like. The NMS is a centralized suite of software and hardware used to monitor, control, and administer the network infrastructure. The NMS is responsible for a wide range of tasks such as fault management, configuration management, security management, performance management, and accounting management. The NMS enables network operators to efficiently manage and optimize network resources, ensuring that the network delivers high performance, reliability, and security.

[0085] Various techniques described herein may also be applied to a cyberphysical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question may have inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

[0086] 5G enables using multiple-input and 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.

[0087] In 5G wireless communication networks, access nodes and / or UEs may have multiple radio interfaces, such as below 6 gigahertz (GHz), centimeter wave (cmWave) and millimeter wave (mmWave), and also being integrable with legacy radio access technologies, such as LTE. Integration with LTE may be implemented, for example, as a system, where macro coverage may be provided by LTE, and 5G radio interface access may come from small cells by aggregation to LTE. In other words, a 5G wireless communication network may support both inter-RAT operability (such as interoperability between LTE and 5G) and inter-RI operability (inter-radio interface operability, such as between below 6GHz, cmWave, and mmWave).

[0088] In one embodiment, an access node 104 may comprise: a radio unit (RU) 103 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 Fl interface. Such an embodiment of the access node 104 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).

[0089] 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 104. The CU 108 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 104. The CU 108 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 104.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 104. The operations of the DU 105 may be at least partly controlled by the CU 108. It should also be understood that the distribution of functions between the DU 105 and the CU 108 may vary depending on the implementation.

[0090] 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 application-specific integrated circuit (ASIC) or customer-specific standard product (CSSP) system-on-a-chip (SoC).

[0091] Edge cloud may be brought into the radio access network 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) 103 of an access node 104. 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 104. Application of cloud RAN architecture enables RAN real-time functions being carried out at the radio access network (e.g., in a DU 105), and non-real-time functions being carried out in a centralized manner (e.g., in a CU 108).

[0092] 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 110, enabling more extensive network coverage. Possible use cases may include: providing service continuity for machine-to-machine (M2M) or Internet of Things (IoT) devices or for passengers on board of vehicles, or ensuring service availability forcritical communications, and future railway, maritime, or aeronautical communications. Satellite communication may utilize geostationary earth orbit (GEO) satellite systems, or low earth orbit (LEO) satellite systems, such as megaconstellations (i.e., systems in which hundreds of (nano)satellites are deployed). Alternatively, the satellites may be an airborne devices, such as an unmanned aerial vehicle (UAV), or a high-altitude platform system (HAPS). A given satellite 106 may provide communication services on Earth via one or more satellite beams. The one or more satellite beams create one or more cells over a given service area that may be bounded by the field of view of the satellite 106.

[0093] 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 a radio access network, and in practice the radio access network may comprise a plurality of access nodes 104, the UEs 100, 102 may have access to a plurality of radio cells, and the radio 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.

[0094] Additionally, in a geographical area of 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) 104 of FIG. 1 may provide any kind of these cells. A cellular radio network may be implemented as a multilayer access networks including several kinds of radio cells. 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.

[0095] 6G wireless communication networks are expected to adopt flexible decentralized and / or distributed computing systems and architecture and ubiquitous computing, with local spectrum licensing, spectrum sharing, infrastructure sharing, and intelligent automated management underpinned bymobile edge computing, artificial intelligence, short-packet communication and blockchain technologies. Key features of 6G may include intelligent connected management and control functions, programmability, integrated sensing and communication, reduction of energy footprint, trustworthy infrastructure, scalability and affordability. In addition to these, 6G is also targeting new use cases covering the integration of localization and sensing capabilities into system definition to unifying user experience across physical and digital worlds.

[0096] It is envisaged that 7G, which will succeed the 5G and 6G technologies, will be able to satisfy the requirements of extremely high bandwidth, almost zero latency, and universal integration.

[0097] Some example embodiments are described below using principles and terminology of 5G radio access technology without limiting the example embodiments to 5G radio access technology, however.

[0098] 3GPP has introduced Ll / L2-triggered mobility (LTM), also called lower-layer triggered mobility in the literature, which aims to reduce interruption time during handover. LTM is a procedure in which a gNB receives Layer 1 (LI) measurement report(s) from a UE and, based on the measurement reports, the gNB issues a cell switch command signaled via a MAC CE to the UE, thus triggering the LTM cell switch to a target candidate cell. The cell switch command indicates an LTM candidate configuration that the gNB previously prepared and provided to the UE through RRC signaling. One or more other LTM candidate configurations may also be prepared as further candidates for the LTM cell switch. Then the UE switches to the target configuration according to the cell switch command. The cell switch can be made with or without random access. The random access may be needed in case the UE is not aware of a timing advance (TA) of the target configuration. On the other hand, if the UE has the TA of the target configuration, the UE may use RACH-less (cell switch without random access via a random access channel, RACH). However, with the current specification and existing agreements within the 3GPP, there exist scenarios where the UE may have in fact the TA applicable to the target configuration while the TA is not provided in the target configuration. This may result from that two cells may be collocated and, thus, beassociated with the same TA for the UE but the UE is not aware of that. In case of a cell switch to one of the candidate cells, the UE will not use the available TA even if it would be suitable for accessing the candidate cell and will unnecessarily perform a random access (RA) channel-based switch.

[0099] The same applies for the source distributed unit (S-DU), and it may unnecessarily trigger a TA acquisition procedure by sending a Physical downlink control channel (PDCCH) order for acquiring the TA of the primary cell (PCell) of the candidate cell.

[0100] FIG. 2 shows an example embodiment of a wireless communication deployment scenario. In the illustrated wireless communication deployment scenario, the user equipment (UE) 100 is served by cell 0 200 and the UE is configured with LTM with the following candidates: candidate 1, candidate 2 and candidate 3. The candidate 1 is configured as having cell 1 210 as candidate primary cell (PCell) and optionally cell A 201 as candidate secondary cell (SCell) in case carrier aggregation (CA) is configured. Respectively, the candidate 2 is configured as having cell 2 220 as candidate PCell and optionally cell B 202 as candidate SCell in case CA is configured. Furthermore, the candidate 3 is configured as having cell A 201 as candidate PCell and optionally cell 2220 as candidate SCell in case CA is configured.

[0101] FIG. 3 illustrates a schematic representation of an example configuration of a wireless communication deployment scenario. In the illustrated schematic representation an example configuration of a wireless communication deployment scenario is presented in accordance with the 3GPP specifications. The illustrated outline shows the structure of the wireless communication deployment scenario of FIG. 2 according to LTM configuration and includes the associated timing advance groups, TAGs (TAG, timing advance group). In the 3GPP specifications, a primary TAG (PTAG) and a secondary TAG (STAG) have been specified. A PTAG includes a serving primary cell (PCell) and the UE uses the PCell as the as timing reference. A TAG including no PCell is called the STAG, and the UE may use any of the secondary cells (SCells) in the STAG as the timing reference.From the user equipment (UE) perspective, the UE cannot determine that cells 1 and cell 2 are collocated and, hence, have the same timing advance (TA). Therefore, if a cell switch to candidate 2 is triggered and the UE has a valid TA obtained for the primary TAG (PTAG) of candidate 1, which is associated with cell 1, the UE will not use the available TA which is suitable for accessing cell 2 and will unnecessarily perform a random access channel (RACH) based switch.

[0102] In addition, in the presented wireless communication deployment scenario, from the network perspective, the source distributed unit (S-DU) does not know whether cell 1 and cell 2 are collocated. Therefore, it may unnecessarily trigger a TA acquisition procedure by sending a physical downlink control channel (PDCCH) order for acquiring the TA of the PCell of candidate 2, i.e., cell 2, although a valid TA for the PCell of candidate 1, i.e., cell 1, has been acquired and is valid and suitable for accessing cell 2.

[0103] As a solution to the problems described above, a new concept called candidate TAG (CTAG) with cell-switch-configuration-wide scope are introduced. One or multiple CTAGs may be configured per UE. The configuration of the associated time alignment timer (TAT) can be common to all candidate cells within the CTAG. The configuration of the TAT may be common to all CTAGs, in case of multiple CTAGs. The UE maintains a TAT for each of the CTAGs within its capability. For example, the number of TATs may be limited. However, the provision of the CTAG(s) may make the use of the TATs more efficient a common TAT may be used for multiple candidate cells.

[0104] In an embodiment, no TAT is configured to a CTAG comprising a serving cell. The reason is that the TATs for serving cells are already configured to and maintained by the UE according to the serving cell configuration.

[0105] In an embodiment the CTAG(s) is / are configured for cells within a cell switch configuration of the UE. The CTAG(s) may be associated with one or more candidate cells of the cell switch and, optionally, one or more serving cells. The cell switch configuration may refer to an LTM configuration, for example.

[0106] In an embodiment, at least one of the configured CTAG(s) is associated with candidate cells from different candidate configurations for the cell switch.FIG. 4 illustrates a schematic representation of an example configuration of a wireless communication deployment scenario utilising candidate TAGs. In the illustrated schematic representation an example configuration of a wireless communication deployment scenario is presented in which candidate TAGs (CTAGs) are introduced. The illustrated outline shows the structure of the wireless communication deployment scenario of FIG. 2 and includes the associated timing advance groups, TAGs (TAG, timing advance group).

[0107] The introduced CTAG configuration comprises a CTAG identification and a mapping of the PTAG and STAGs of each candidate cell to the CTAGs. In an embodiment, CTAGs associated with the serving PTAG and / or STAG(s) and a corresponding mapping of serving TAGs to CTAGs are also introduced. In FIG. 4 examples of CTAGs are introduced on the left. In FIG. 4 also the mapping of the PTAG and STAGs of candidate 1, of candidate 2, and of candidate 3 of the wireless communication deployment scenario of FIG. 2 are shown.

[0108] In one embodiment, the CU generates the mapping. In another embodiment, the source CU (S-CU) generates the mapping using information provided by the candidate CUs (C-CUs). In another further embodiment, the C-CUs provide collocation information about the candidate cells. In yet another further embodiment, the C-CUs provide mapping of PTAGs and STAGs of the candidate cells they control to CUTAGs, where CUTAGs are CTAGs with a CU-wide scope. In other words, each C-CU may provide, as CUTAG(s), CTAG(s) for cells under its respective control area and mapping(s) of the PTAG(s) and STAG(s) associated with candidate cells they control to these C-CU-wide CTAGs(s).

[0109] In the MAC CE carrying the TA information to the UE, an indication of the CTAG associated with the TA may be provided. The indication may be the CTAG identification described above, e.g. an identifier of the CTAG. As a consequence, upon triggering a cell switch to a candidate cell associated with the CTAG via said mapping, the UE is able to retrieve the TA information for the candidate cell and perform the RACH-less cell switch.

[0110] In an inter-CU setup, indication from C-CUs to S-CU of collocated candidate cells may be provided. This indication may be used so that the S-CU canappropriately configure the CTAG(s), e.g., by consolidating the CUTAGs from multiple CUs. Each CUTAG may form a separate CTAG but, in some cases, some CUTAGs may be combined into a single CTAG.

[0111] In an embodiment, an indication of configured CTAG(s) and mappings of TAGs of individual candidates to the CTAGs may be provided to the source DU (S-DU) and candidate DUs (C-DUs). Using this indication, the S-DU and C-Dus, when serving the UE, they can decide for which cells they should issue a PDCCH order and avoid unnecessary triggering of early TA acquisition procedure for cells for which a valid TA is already available.

[0112] In one embodiment, reception of a CTAG configuration and mapping of TAGs of individual candidate(s) to CTAG(s), along with configuration of UE-based TA estimation at a UE may cause the UE to perform UE based TA measurements applicable for all the candidate cells linked to the CTAG.

[0113] In another embodiment, the CTAG is known only at the target DU side. Once the UE sends a preamble for a cell belonging to a CTAG, the target DU may send the TA value along with the candidate cell IDs for which the TA value may be used. It is up to source DU to forward the TA to the UE along with the IDs of the candidate cell(s) for which it should apply it.

[0114] At the UE, when receiving a MAC CE carrying TA information as well as a CTAG index, the UE stores the TA information alongside the CTAG index. Also at the UE, when executing a cell switch, such as the LTM or a conditional LTM cell switch, the UE may retrieve the TA information by accessing the CTAG associated with the target cell and retrieving TA information of the CTAG. In an embodiment, at the UE, when receiving a cell switch command where the TA information is missing, the UE retrieves the TA information from the CTAG associated with the target cell.

[0115] FIG.5 illustrates an example embodiment of a flow diagram of a wireless communication deployment scenario utilising candidate TAGs. In the presented example embodiment of a wireless communication deployment scenario utilising candidate TAGs, at the UE, it is first received 501 over a wireless network connection, at least a first candidate configuration and a second candidateconfiguration for a conditional layer 1 / layer 2 triggered mobility, LTM, cell switch. After receiving the candidate configurations, at the UE, it is received 502 over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group, TAG, associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification, and wherein a TAG of a candidate cell of the first candidate configuration is mapped to the same CTAG configuration as a TAG of a serving cell or a TAG of a candidate cell of the second candidate configuration. After this, at the UE, it is started 503, based on receiving a timing advance, TA value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification. Thereafter, based on detecting that a condition for a cell switch to the candidate cell of the first candidate configuration is met, obtain TA value for the candidate cell of the first candidate configuration is obtained 504 by using the CTAG configuration and the cell switch to the candidate cell of the without random access is performed 505.

[0116] FIG. 6 illustrates another example embodiment of a flow diagram of a wireless communication deployment scenario utilising candidate TAGs. In the presented another example embodiment of a wireless communication deployment scenario utilising candidate TAGs, at the UE, it is first received 601 over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification. After receiving, at the UE, it is started 602, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification. Thereafter, in a case when a cell switch is to be performed to a candidate cell of the CTAG identification and the TAT associated with the CTAG identification is running, performing the cell switch is performed 603 without random access.

[0117] FIG. 7 illustrates a third example embodiment of a flow diagram of awireless communication deployment scenario utilising candidate TAGs. In the presented third example embodiment of a wireless communication deployment scenario utilising candidate TAGs, at the network node, it is first obtained 701 at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification. After obtaining, at the network node, it is transmitted 702, over a wireless network connection, at least one CTAG configuration to user equipment for cell switch of the user equipment.

[0118] FIG. 8 illustrates an example embodiment of a message sequence chart of a wireless communication deployment scenario utilising candidate TAGs. In step 901 the UE sends the measurement report to the CU via the S-DU and the CU decides to configure LTM for the UE. The CU proceeds with the UE context setup / modification procedures 902 with the source and C-DUs, which include configuration of conditional LTM (CLTM) conditions. In the example shown in FIG.

[0119] 8, CLTM conditions are prepared by the DUs. In one embodiment DUs prepare LI measurement-based CLTM conditions for triggering a conditional cell switch from a source cell to one of the candidate cells. Alternatively, CLTM conditions may be prepared by the CU, e.g., when the CLTM conditions are based on L3 measurements.

[0120] In an inter-CU setup, the S-DU sends a handover request to a C-CU for each of the LTM candidates controlled by the C-CU. In the handover request acknowledge messages, the C-CU sends an indication of collocated candidate cells. For example, in an embodiment, the indication may be provided by mapping candidate cells to CUTAGs, where CUTAGs are CTAGs with C-CU-wide scope, as described above.

[0121] If two candidate cells, potentially under different candidate configurations, have the same cell-to-CUTAG mapping, the S-CU can associate them with the same CTAG.

[0122] For example, let us assume that cells 3, 4 and 5 are candidate cells controlled by C-CU 1 and cells 3 and 4 are collocated. We also assume that the following two candidate configurations are prepared by C-CU 1 for the cell switchof the UE. This gives us the candidate configuration 1: cell 3 as the PCell and cell 5 as SCell, and the candidate configuration 2: cell 4 as the PCell and cell 3 as SCelL Accordingly, in the handover request acknowledge including candidate configuration 1, C-CU 1 includes the indication that the PCell / cell 3 belongs to CUTAG 0 and the SCell / cell 5 to CUTAG 1. The same or a different handover request acknowledge message may also indicate candidate configuration 2, wherein C-CU provides the indication that the PCell / cell 4 belongs to CUTAG 0 and the SCell / cell 3 to CUTAG 0. The S-CU receives the mappings to the CUTAG 0 and CUTAG 1, and determines that cell 3 and cell 4 both mapped to the same CUTAG 0 may be associated with the same CTAG. So, in general, if two (or more) cells belonging to different candidate configurations are mapped to the same CUTAG, the S-CU may associate the two (or more) cells to the same CTAG. In another embodiment, when all candidate configurations provided by a C-CU are included in the same handover request acknowledge message, instead of CUTAGs and mappings of TAGs of candidate cells to the CUTAGs, the C-CU may provide lists of collocated candidate cell. For the example described above, the C-CU would provide two lists, one list comprising IDs of cell 3 and cell 4 and another list comprising ID of cell 5.

[0123] The CU provides to the S-DU 903 and C-DUs 904 within a UE context modification request the configuration of CTAGs and the mapping of PTAG and STAGs to CTAG(s).

[0124] In one embodiment, a CTAG configuration includes the CTAG ID and the duration of the associated TAT. In an alternative embodiment, the TAT for all CTAGs may be configured with the same duration. In this case, the configuration of CTAGs includes only a single value for the TAT duration, applicable to all TATs associated with CTAGs to be maintained by the UE. The number of CTAGs and TATs to be maintained in this case is inferred by the number of CTAGs indicated in the mappings of PTAGs and STAGs of all candidates and serving configurations to CTAGs.

[0125] The configuration of CTAGs comprises in one embodiment, the mapping of PTAG and STAGs to CTAGs for each candidate and for the serving configuration. The CU provides to the DUs a list whose elements have an index that is thecandidate’s TAG, e.g., 0 for PTAG, 1 for first STAG, 2 for second STAG and so on, and a value that indicates the associated CTAG.

[0126] In an alternative embodiment, in an inter-CU setup, the S-CU provides the aforementioned information to the C-CUs in LTM configuration update messages, so that they in turn provide it to the candidate DUs they control in UE context modification request messages.

[0127] After this the CU sends 905, 906 the RRC reconfiguration to the UE via the S-DU. The RRC configuration includes the CLTM condition configuration for the initial and subsequent conditional LTM cell switches. The configuration of CTAGs and, for each candidate and (optionally) for the serving configuration, the mapping of PTAG and STAGs to CTAGs, as in steps 903, 904.

[0128] One exemplary implementation of an embodiment is shown below: LTM-Config-r18 ::= SEQUENCE {

[0129] ltm-ReferenceConfiguration-r18 SetupRelease {ReferenceConfiguration-r18} OPTIONAL, -- Need M

[0130] ltm-CandidateToReleaseList-r18 SEQUENCE (SIZE (1..maxNrofLTM-Configs-r18)) OF LTM-CandidateId-r18 OPTIONAL, -- Need N ltm-CandidateToAddModList-r18 SEQUENCE (SIZE (1..maxNrofLTM-Configs-r18)) OF LTM-Candidate-r18 OPTIONAL, -- Need N ltm-ServingCellNoResetID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need N

[0131] ltm-CSI-ResourceConfigToAddModList-r18 SEQUENCE (SIZE (1..maxNrofLTM-CSI-ResourceConfigurations-r18)) OF LTM-CSI-ResourceConfig-r18

[0132] OPTIONAL, - Need N

[0133] ltm-CSI-ResourceConfigToReleaseList-r18 SEQUENCE (SIZE (1..maxNrofLTM-CSI-ResourceConfigurations-r18)) OF LTM-CSI-ResourceConfigId-r18

[0134] OPTIONAL, - Need N1

[0135] attemptLTM-Switch-rl8 ENUMERATED {true} OPTIONAL, - Cond LTM-MCG

[0136] ltm-ServingCellUE-MeasuredTA-ID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need N

[0137] ltm-ServingCellTAGsToCTAGs SEQUENCE (SIZE (1..maxNrofTAGs)) OF CTAG-Id OPTIONAL, -- Need N,

[0138] ltm-CTAG-Config LTM-CTAG-Config,

[0139] }

[0140] LTM-CTAG-Config::= SEQUENCE {

[0141] ltm-ctag-ToReleaseList SEQUENCE (SIZE (1..maxNrofCTAGs)) OF CTAG-Id OPTIONAL, -- Need N

[0142] ltm-ctag-ToAddModList SEQUENCE (SIZE (1..maxNrofCTAGs)) OF CTAG OPTIONAL -- Need N

[0143] }

[0144] CTAG::= SEQUENCE {

[0145] ctag-Id CTAG-Id,

[0146] timeAlignmentTimer TimeAlignmentTimer,

[0147] }

[0148] CTAG-Id ::= INTEGER (0..maxNrofCTAGs-1)

[0149] LTM-Candidate-r18 ::= SEQUENCE {

[0150] ltm-CandidateId-r18 LTM-CandidateId-r18, ltm-CandidatePCI-r18 PhysCellId OPTIONAL, -- Need Mltm-SSB-Config-r18 LTM-SSB-Config-r18 OPTIONAL, -- Need M

[0151] ltm-CandidateConfig-r18 OCTET STRING (CONTAINING RRCReconfiguration) OPTIONAL, -- Need M

[0152] ltm-ConfigComplete-r18 ENUMERATED {true} OPTIONAL, -- Need R

[0153] ltm-EarlyUL-SyncConfig-r18 OCTET STRING (CONTAINING EarlyUL-SyncConfig-r18) OPTIONAL, -- Need R

[0154] ltm-EarlyUL-SyncConfigSUL-r18 OCTET STRING (CONTAINING EarlyUL-SyncConfig-r18) OPTIONAL, -- Need R

[0155] ltm-TCI-Info-r18 LTM-TCI-Info-r18 OPTIONAL, -- Need M

[0156] ltm-NoResetID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need M

[0157] ltm-UE-MeasuredTA-ID-r18 INTEGER (1..maxNrofLTM-Configs-plus1-r18) OPTIONAL, -- Need M

[0158] ltm-TAGsToCTAGs SEQUENCE (SIZE (1..maxNrofTAGs)) OF CTAG-Id OPTIONAL, -- Need N,

[0159] }

[0160] In another embodiment, a mapping of TAG(s) to CTAG(s) is provided as a list of pairs of TAG ID and associated CTAG ID. In another embodiment, a mapping of TAG(s) to CTAG(s) is provided as two lists of same length, wherein, given an index, the indexed element of the first list comprises a TAG ID and the indexed element of the second list comprises an associated CTAG ID.

[0161] A special case of the proposed solution is when early UL synchronization is performed only for the PCell of the candidates, as done for 3GPP Rel-18 and Rel-19 LTM. Instead of lists Itm-ServingCellTAGsToCTAGs and Itm-TAGsToCTAGs, a single value ltm-ServingCellCTAG of type CTAG-Id and a single value ltm-CTAG of type CTAG-Id per candidate are needed.

[0162] In one embodiment, the configuration of ltm-CTAG-config, ltm-ServingCellTAGsToCTAGs and ltm-TAGsToCTAGs may be conditioned on CLTM conditions being configured for at least two CLTM candidates. In another embodiment, the configuration of ltm-CTAG-config, ltm-ServingCellTAGsToCTAGs and ltm-TAGsToCTAGs may be conditioned on at least two candidate cells (within or across candidates) belonging to the same CTAG.

[0163] Furthermore, in one embodiment, no TAT is configured for the CTAG which is associated with a source cell, as a TATs for source cells are already configured to and maintained by the UE according to the serving cell group configuration. In a further embodiment, CTAG-Id=0 is always used for the source PTAG. Additionally, if CA is used, the first CTAG-Ids are used for the source TAGs. For example, if the source cell group configuration has the PTAG and an STAG, then CTAG-Id=0 is used for the source PTAG and CTAG-Id=1 is used for the serving STAG.

[0164] The UE may send an RRC reconfiguration complete message to the S-DU, which may be forwarded to CU. The UE may send a measurement report to the S-DU or to the CU. Based on L1 / L3 measurement report provided by the UE to the S-DU / CU or upon a UE-side event trigger, early DL synchronization takes place.

[0165] Based on L1 / L3 measurement report provided by the UE to the S-DU / CU, the S-DU issues a PDCCH order 911 to the UE to perform random access preamble transmission for early TA acquisition for cell 1. Consequently, the UE performs random access preamble transmission 912 to cell 1, as ordered by S-DU.

[0166] Thereafter, using the received random access preamble, the C-DU computes the TA. For the TA information transfer from the C-DU to the S-DU, we consider the following two options. As first option, the C-DU sends to the S-DU via the CU the computed TA along with the associated candidate cell ID. Using its knowledge of the TAG associated to the candidate cell (ID) within the candidate’s cell group configuration and the configured TAG to CTAG mapping, the S-DU determines the associated CTAG ID for the received TA. As second option, by usingits knowledge of the TAG associated to the candidate cell (ID) within the candidate’s cell group configuration and the configured TAG to CTAG mapping, the C-DU determines the associated CTAG ID for the computed TA. The C-DU sends to the S-DU via the CU the computed TA along with the associated CTAG ID. In one embodiment it is not the C-DU but the CU appends the CTAG id to the TA forwarding message 913, 914.

[0167] If the candidate cell is configured with conditional LTM cell switch execution conditions: The S-DU sends 915 to the UE the TA. In one embodiment, along with the TA, the S-DU sends the associated CTAG ID. This is the most compact way to provide the required association information of the provided TA, as the number of CTAGs is smaller or equal to the number of cells configured with early UL sync configuration. In another embodiment, the TA and the CTAG ID are sent using a new MAC CE. In another alternative embodiment, the TA and the CTAG ID are sent using an (absolute) timing advance command (TAC) MAC CE. In yet another alternative embodiment, along with the TA, the S-DU sends an indication of the associated candidate cell.

[0168] If not indicated in using the indicated candidate cell, its knowledge of the TAG it is associated with and the configured TAG to CTAG mapping, it determines the CTAG ID associated with the received TA. Having determined the CTAG ID, the UE starts or restarts the TAT associated with the CTAG, setting its duration according to the configuration. We note that the UE maintains CTAG-associated TATs, whose number may be smaller or equal to the number of CTAGs, up to UE capability.

[0169] For the cell switch handover 920, the following two cases can be considered: a conditional LTM cell switch, and a network-triggered LTM cell switch. In a conditional LTM cell switch a CLTM condition is satisfied and conditional LTM cell switch to a candidate, e.g., candidate having cell 2 as PCell, is triggered. By using the triggered candidate, which contains one or more candidate cells, its knowledge of the TAG(s) with which the triggered candidate cell(s) are associated and the configured TAG to CTAG mapping, the UE determines the CTAG ID(s) with which the triggered candidate cell(s) are associated and determines thatit has valid TA(s) for the determined CTAG(s). The UE applies the target configuration and uses the TA(s) of the determined CTAG(s) for RACH-less cell switch.

[0170] In a network-triggered LTM cell switch, the UE sends a measurement report. If it is a LI measurement report, it is sent to the S-DU. In case it is a L3 measurement report, it is sent to the CU. The S-DU / CU determines cell switch triggering to a candidate, referred to in the following as target, e.g., candidate that has cell 2 as PCell, based on the measurement report. If the CU decides cell switch, it notifies the S-DU. Using knowledge of the TAG(s) with which the target cell(s) are associated and the configured TAG to CTAG mapping, the S-DU determines the CTAG ID(s) with which the target cell(s) are associated and determines that it has valid TA(s) for the determined CTAG(s). The S-DU sends a cell switch command (CSC) MAC CE to the UE, indicating the target configuration ID, e.g., the candidate configuration that has cell 2 as the PCell. The CSC contains also the TA(s) that are available for the TAGs of the target. The UE applies the target configuration and uses the indicated TA(s) for RACH-less cell switch.

[0171] The UE performs RACH-less LTM switch and transmits the RRCReconfigurationComplete message 921, 922 to the target. The cell switch is completed 930.

[0172] In one embodiment, UE may maintain the CTAG obtained before the cell switch command. In a related embodiment, the CTAG values indicated to the UE maybe send to the new S-DU by the last S-DU of the UE after cell switch.

[0173] In another embodiment, UE may delete all CTAGs except the CTAG that it applied during the cell switch.

[0174] In a third embodiment, UE may store the PTAG of the last source cell, after cell switch, as the CTAG mapping to the last source cell, in case the last source cell is also prepared as an LTM candidate cell.

[0175] In a fourth embodiment, the CTAG configuration and the mapping of PTAGs and STAGs of candidates are not provided to the UE and the invention is implemented on the network side in a UE-transparent manner.

[0176] In a fifth embodiment, the network provides TA information withoutindicating the CTAG (as it is not know to the UE), e.g., indicating the candidate ID. Then, the UE maintains the TA and the corresponding TAT in a candidate-specific manner. For reusing the same TA at another collocated candidate, the S-DU determines that the TA can be used by another candidate and provides the same TA with another MAC CE for the other candidate (e.g, include the ID of the other candidate).

[0177] In a sixth embodiment, the S-DU can indicate the TA obtained for a candidate in a cell switch command to another candidate, after determining that the TA for these candidates is the same and valid, using the CTAG configuration and PTAGs and STAGs to CTAGs mapping. The benefit of this approach is that it has less specification impact.

[0178] FIG. 9 illustrates an example of an apparatus comprising means for performing one or more of the example embodiments described above. For example, the apparatus 9700 may be an apparatus such as, or comprising, or comprised in, a user equipment (UE) 100, 102. The user equipment 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.

[0179] The apparatus 9700 may comprise a circuitry, a module or a chipset applicable for realizing one or more of the example embodiments described above. For example, the apparatus 9700 may comprise at least one processor 9710. The at least one processor 9710 interprets instructions (e.g., computer program instructions) and processes data. The at least one processor 9710 may comprise one or more programmable processors. The at least one processor 9710 may comprise programmable hardware with embedded firmware and may, alternatively or additionally, comprise one or more application-specific integrated circuits (ASICs).

[0180] The at least one processor 9710 is coupled to at least one memory 9720. The at least one processor is configured to read and write data to and from the at least one memory 9720. The at least one memory 9720 may comprise one or more memory units. The memory units may be volatile or non-volatile. It is to be notedthat 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 9720 stores computer readable instructions that are executed by the at least one processor 9710 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 9710 executes the instructions using volatile memory for temporary storage of data and / or instructions. The computer readable instructions may refer to computer program code.

[0181] The computer readable instructions may have been pre-stored to the at least one memory 9720 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 9710 causes the apparatus 9700 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.

[0182] 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).

[0183] The apparatus 9700 may further comprise, or be connected to, an input unit 9730. The input unit 9730 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 9730 may comprise an interface to which external devices may connect to.

[0184] The apparatus 9700 may also comprise an output unit 9740. 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 9740 may further comprise one or more audio outputs. The one or more audio outputs may be for example loudspeakers.

[0185] The apparatus 9700 further comprises a connectivity unit 9750. The connectivity unit 9750 enables wireless connectivity to one or more external devices. The connectivity unit 9750 comprises at least one transmitter and at least one receiver that may be integrated to the apparatus 9700 or that the apparatus 9700 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 9750 may comprise an integrated circuit or a set of integrated circuits that provide the wireless communication capability for the apparatus 9700. Alternatively, the wireless connectivity may be a hardwired application-specific integrated circuit (ASIC). The connectivity unit 9750 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 9750 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.

[0186] It is to be noted that the apparatus 9700 may further comprise various components not illustrated in FIG. 9. The various components may be hardware components and / or software components.

[0187] FIG. 10 illustrates an example of an apparatus 9800 comprising means for performing one or more of the example embodiments described above. For example, the apparatus 9800 may be an apparatus such as, or comprising, or comprised in, an access node 104 of a radio access network.

[0188] The apparatus 9800 may comprise, for example, a circuitry, a module or a chipset applicable for realizing one or more of the example embodiments described above. The apparatus 9800 may be an electronic device comprising one or more electronic circuitries. The apparatus 9800 may comprise a communication control circuitry 9810 such as at least one processor, and at least one memory 9820 storing instructions 9822 which, when executed by the at least one processor, cause the apparatus 9800 to carry out one or more of the example embodiments described above. Such instructions 9822 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.

[0189] The processor is coupled to the memory 9820. The processor is configured to read and write data to and from the memory 9820. The memory 9820 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-transitorycomputer 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 9820 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.

[0190] The computer readable instructions may have been pre-stored to the memory 9820 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 9800 to perform one or more of the functionalities described above.

[0191] The memory 9820 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.

[0192] The apparatus 9800 may further comprise or be connected to a communication interface 9830, 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 9830 comprises at least one transmitter (Tx) and at least one receiver (Rx) that may be integrated to the apparatus 9800 or that the apparatus 9800 may be connected to. The communication interface 9830 may provide means for performing some of the blocks and / or functions (e.g., transmitting and receiving) for one or more example embodiments described above. The communication interface 9830 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.

[0193] The communication interface 9830 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 UEs 100, 102. The apparatus 9800 may further comprise or be connected to another interface towards a core network 110, such as the network coordinator apparatus or AMF, and / or to the access nodes 104 of the wireless communication network.

[0194] The apparatus 9800 may further comprise a scheduler 9840 that is configured to allocate radio resources. The scheduler 9840 may be configured along with the communication control circuitry 9810 or it may be separately configured.

[0195] It is to be noted that the apparatus 9800 may further comprise various components not illustrated in FIG. 10. The various components maybe hardware components and / or software components.

[0196] FIG. 11 illustrates an example of an apparatus according to some embodiments of the present invention in connection with the user equipment. FIG.

[0197] 11 illustrates an apparatus configured to carry out the functions described above in connection with the user equipment. Each apparatus 500 may comprise one or more communication control circuitry, such as at least one processor 502, and at least one memory 504, including one or more algorithms 503, such as a computer program code (software) wherein the at least one memory and the computer program code (software) are configured, with the at least one processor, to cause the apparatus to carry out any one of the exemplified functionalities of the user apparatus. The apparatus may further comprise different communication interfaces 501 and one or more user interfaces 501’.

[0198] FIG. 12 illustrates an example of an apparatus according to some embodiments of the present invention in connection with the network node. FIG.

[0199] 12 illustrates an apparatus configured to carry out the functions described above in connection with the network node. Each apparatus 600 may comprise one ormore communication control circuitry, such as at least one processor 602, and at least one memory 604, including one or more algorithms 603, such as a computer program code (software) wherein the at least one memory and the computer program code (software) are configured, with the at least one processor, to cause the apparatus to carry out any one of the exemplified functionalities of the network node. The apparatus may further comprise different communication interfaces 601 and one or more user interfaces 601’.

[0200] The apparatus may be an any electronic device of any kind, such as, and not limited to, user equipments and other electronic devices that may require such a memory apparatus. The apparatus may may be any electrical device connectable to an access network and configurable to be in a wireless connection on one or more communication channels, including one or more control channels, with an access network component, e.g. an access network apparatus, providing a cell, for example. The physical link from the apparatus to the access network towards a core network is called an uplink or a reverse link and the physical link to the apparatus is called a downlink or a forward link. By way of example rather than limitation, the apparatus may referred to as a served apparatus, a downlink apparatus, a mobile apparatus, a terminal device, a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). A non-limiting lists of examples of the apparatus, or what the apparatus may comprise or be comprised in, include a mobile phone, a cellular phone, a smart phone, a voice over internet protocol (VoIP) phone, a wireless local loop phone, a device using a wireless modem, a portable computer, a desktop computer, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), a smart device, a multimedia device, an image capture terminal device, such as a digital camera, a gaming terminal device, a music storage and playback appliance, a drone, a vehicle, an automated guided vehicle, an autonomous connected vehicle, a vehicle-mounted wireless terminal device, a wireless endpoint, an internet of things device, an industrial internet of things device, a device operating in an industrial and / or an automated processing chain contexts, a consumer electronics device, a consumer internet of things device, amobile robot, a mobile robot arm, a sensor, a surveillance camera, an eHealth related device, a medical monitoring device, a medical device, for example for remote surgery, a wearable device, such as a smart watch, a smart ring, a headmounted display (HMD), an on-person device, etc. The apparatus may also be part of a group of apparatuses seen as one apparatus, i.e. one mobile apparatus, by the wireless network.

[0201] The apparatus may be any access network component of an access network. An access network domain may be based on any kind of an access network, such as a cellular access network, for example 5G network, 5G-Advanced network, 6G network, etc., a non-terrestrial network, a legacy cellular radio access network, for example 4G or older generation network, or a non-cellular access network, for example a wireless local area network, or any combination thereof. To provide the wireless access, the access network comprises access network components, such as access network apparatuses, or access devices. An access device component may provide one or more cells, possibly with different cell accessibility per a cell, but a cell is provided by one access device. However, there may be overlapping cells, for example a macro cell provided by an access device operating in co-operation of access nodes providing smaller cells, such as micro-, femto- or picocells, which overlap at least partly within the macro cell. There are a wide variety of access network components. A non-limiting lists of examples of the access network component, include different types of base stations, such as eNBs, gNBs, split gNBs, transmission-reception points, network-controlled repeaters, nodes operationally coupled to one or more remote radio heads, satellites, donor nodes in integrated access and backhaul (IAB), fixed IAB nodes, mobile IAB nodes mounted on vehicles, for example, etc. At least some of the apparatuses in the access network may provide an abstraction platform to separate abstractions of network functions from the processing hardware.

[0202] Further, it should be noted that some of the components may be multidomain components. For example a device component may also provide services to other device components, i.e. operate also as an access network component, for example be a relay node, or a mobile IAB node, or a mobile termination part in anIAB node. Hence, herein term mobile apparatus is used for device components, or device component functionality in a multi-domain component and term access network apparatus is used for access network components or access network component functionality in a multi-domain component.

[0203] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0204] 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 the processor. 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 ofthe 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.

[0205] Compared to the present cellular network technologies, the proposed invention has the advantage that the UE and / or the S-DU can determine that cells under different candidates have the same TA. Hence, the UE avoids unnecessary RACH-based cell switch to a cell, although it may (unknowingly) already have a valid TA for accessing it. In addition, the unnecessary early TA acquisition is avoided, either by avoiding issuing an unnecessary PDCCH order from the S-DU to the UE or by avoiding unnecessary UE-based TA estimation for a candidate cell for which the required TA is already available.

[0206] It will be obvious to a person skilled in the art that, as technology advances, the inventive concept may be implemented in various ways within the scope of the claims. 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

CLAIMS1. A device comprising:at least one processor, andat least one memory storing instructions that, when executed by the at least one processor, cause the device at least to:receive, over a wireless network connection, at least a first candidate configuration and a second candidate configuration for a conditional layer 1 / layer 2 triggered mobility, LTM, cell switch;receive, over the wireless connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group, TAG, associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification, and wherein a TAG of a candidate cell of the first candidate configuration is mapped to the same CTAG configuration as a TAG of a serving cell or a TAG of a candidate cell of the second candidate configuration;start, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; andbased on detecting that a condition for a cell switch to the candidate cell of the first candidate configuration is met, use the received TA value for the candidate cell of the first candidate configuration by using the CTAG configuration and perform the cell switch to the candidate cell of the first candidate configuration without random access.

2. The device according to claim 1, wherein the first candidate configuration, the second candidate configuration, the CTAG configuration, and conditions for triggering the conditional LTM cell switch are received via radio resource control signalling.

3. The device according to claim 1 or to claim 2, wherein the mapping is formed by an identifier of the timing advance group associated with the serving cell or a candidate cell of a cell switch, wherein the identifier is received in connection with the CTAG identification.

4. The device according to any of claims 1 to 3, configured to determine, when the cell switch is to be performed to a candidate cell, the TA value to be used to access the candidate cell to be equal to the TA value associated with the CTAG to which the TAG of the candidate cell has been mapped.

5. The device according to claim 4, wherein the timing advance group of the candidate cell of the first configuration is a primary timing advance group or a secondary timing advance group.

6. The device according to any of claims 1 to 5, wherein the CTAG configuration is mapped to a primary TAG of a serving cell.

7. The device according to any of claims 1 to 5, wherein the CTAG configuration is mapped to a secondary TAG of a serving cell.

8. The device according to claim 6 or claim 7, wherein no TAT is configured for the CTAG configuration.

9. The device according to any of claims 1 to 5, wherein the CTAG configuration is mapped to a TAG that contains no serving cells.

10. The device according to any of claims 1 to 9, whereinthe device comprises or is comprised in a user equipment.

11. A method, comprising:receiving, over a wireless network connection, at least a first candidate configuration and a second candidate configuration for a conditional layer 1 / layer 2 triggered mobility, LTM, cell switch;receiving, over a wireless network connection, at least one candidate timing advance group, CTAG, configuration comprising a CTAG identification and a mapping of a timing advance group, TAG, associated with a serving cell or a candidate cell of a cell switch to the CTAG identification, wherein collocated cells, if any, are mapped to the same CTAG identification, and wherein a TAG of a candidate cell of the first candidate configuration is mapped to the same CTAG configuration as a TAG of a serving cell or a TAG of a candidate cell of the second candidate configuration;starting, based on receiving a timing advance, TA, value for the CTAG identification, a time alignment timer, TAT, associated with the CTAG identification; andbased on detecting that a condition for a cell switch to the candidate cell of the first candidate configuration is met, using the received TA value for the candidate cell of the first candidate configuration by using the CTAG configuration and performing the cell switch to the candidate cell of the without random access.

12. The method according to claim 11, wherein the first candidate configuration, the second candidate configuration, the CTAG configuration, and conditions for triggering the conditional LTM cell switch are received via radio resource control signalling.

13. The method according to claim 11 or to claim 12, wherein the mapping is formed by an identifier of the timing advance group associated with the serving cell or a candidate cell of a cell switch, wherein the identifier is received in connection with the CTAG identification.

14. The method according to any of claims 11 to 13, wherein, when the cell switch is to be performed to a candidate cell, the TA value to be used to accessthe candidate cell is determined to be equal to the TA value associated with the CTAG to which the TAG of the candidate cell has been mapped.

15. The method according to any of claims 14, wherein the timing advance group of the candidate cell of the first configuration is a primary timing advance group or a secondary timing advance group.

16. The method according to any of claims 11 to 15, wherein the CTAG configuration is mapped to a primary TAG of a serving cell.

17. The method according to any of claims 11 to 15, wherein the CTAG configuration is mapped to a secondary TAG of a serving cell.

18. The method according to claim 16 or claim 17, wherein no TAT is configured for the CTAG configuration.

19. The method according to any of claims 11 to 15, wherein the CTAG configuration is mapped to a TAG that contains no serving cells.

20. The method according to any of claims 11 to 19, wherein the method is carried out in a user equipment.

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