Leave indication for conditional cell switch

Abstract

Disclosed is a method comprising receiving, by a user device, from an access node of a first cell, configuration information related to a conditional cell 5 switch procedure, the configuration informa

Description

FIELD

[0001] The following example embodiments relate to wireless communication. BACKGROUND

[0002] In wireless communication, a cell switch refers to a procedure by which the connection of a user device may be transferred from one cell to another, while preserving the ongoing voice call or data session. SUMMARY

[0003] 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.

[0004] According to a first aspect, there is provided a user device comprising: means for receiving, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; means for determining whether the one or more conditions are fulfilled; and means for transmitting, to the access node of the first cell, based on determining that the one or more conditions are fulfilled, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells, wherein the leave indication is transmitted before performing the conditional cell switch procedure.

[0005] According to a second aspect, there is provided the user device of the first aspect, wherein the leave indication comprises at least one of: an identifier of at least the second cell for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell, information of one or more beams from the second cell for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell.

[0006] According to a third aspect, there is provided the user device of the first or second aspect, wherein the leave indication is comprised in a medium access control control element message or a radio resource control message.

[0007] According to a fourth aspect, there is provided the user device of the first or second aspect, further comprising: means for performing one or more radio measurements associated with the one or more conditions on at least the second cell,

[0008] wherein the leave indication is comprised in a measurement report for reporting the one or more radio measurements, and / or wherein the means for transmitting the leave indication are configured to transmit the leave indication based on obtaining a predefined number of measurements samples.

[0009] According to a fifth aspect, there is provided the user device of the fourth aspect, further comprising: means for starting a timer that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the means for starting the timer are configured to start the timer based on transmitting the leave indication; means for determining, based on detecting that the timer has expired, whether one or more radio conditions on the first cell and the second cell are above a threshold; and means for transmitting another measurement report to the access node of the first cell, based on determining that the one or more radio conditions on the first cell and the second cell are above the threshold.

[0010] According to a sixth aspect, there is provided the user device of any of the first to fourth aspects, further comprising: means for starting a timer that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the means for starting the timer are configured to start the timer based on transmitting the leave indication; means for determining, based on detecting that the timer has expired, whether one or more radio conditions on the first cell are above a threshold; and means for refraining from performing the conditional cell switch procedure from the first cell to the second cell, based on determining that the one or more radio conditions on the first cell are above the threshold.

[0011] According to a seventh aspect, there is provided the user device of any of the first to fourth aspects, further comprising: means for starting a timer that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the means for starting the timer are configured to start the timer based on transmitting the leave indication; means for determining, based on detecting that the timer has expired, whether one or more radio conditions on the first cell are below a threshold; and means for performing the conditional cell switch procedure, based on determining that the one or more radio conditions on the first cell are below the threshold.

[0012] According to an eighth aspect, there is provided the user device of any of the first to fifth aspects, further comprising: means for performing the conditional cell switch procedure based on transmitting the leave indication, wherein the means for transmitting the leave indication are configured to transmit the leave indication at a predefined point in time.

[0013] According to a ninth aspect, there is provided the user device of any of the first to fifth aspects, further comprising: means for determining whether a response to the leave indication has been received from the access node of the first cell within a pre-defined time period; and means for refraining from performing the conditional cell switch procedure, based on determining that the response has not been received within the pre-defined time period.

[0014] According to a tenth aspect, there is provided the user device of any of the first to fifth aspects, further comprising: means for receiving, from the access node of the first cell, a response to the leave indication, wherein the response indicates a permission for performing the conditional cell switch procedure; and means for performing the conditional cell switch procedure based on receiving the response from the access node of the first cell.

[0015] According to an eleventh aspect, there is provided the user device of the tenth aspect, further comprising: means for initiating the conditional cell switch procedure based on transmitting the leave indication; means for stopping the conditional cell switch procedure at a pre-defined point; and means for continuing the conditional cell switch procedure from the pre-defined point based on receiving the response to the leave indication from the access node of the first cell.

[0016] According to a twelfth aspect, there is provided the user device of any of the ninth to eleventh aspects, wherein the response comprises at least one of: a cell switch command for performing the conditional cell switch procedure, a transmission configuration indicator state activation command associated with the second cell, a physical downlink control channel order requesting the user device to start a randomaccess procedure with the second cell, a downlink control information message, a handover command in a radio resource control message, or a medium access control control element message.

[0017] According to a thirteenth aspect, there is provided an access node of a first cell, the access node comprising: means for transmitting, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; means for receiving, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells; means for generating, based on receiving the leave indication, a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; and means for transmitting the message to the access node of the second cell.

[0018] According to a fourteenth aspect, there is provided the access node of the thirteenth aspect, wherein the message comprises context information associated with the user device.

[0019] According to a fifteenth aspect, there is provided the access node of the thirteenth or fourteenth aspect, wherein the leave indication received from the user device comprises information of one or more beams from the second cell for which the one or more conditions were fulfilled, wherein the message transmitted to the access node of the second cell comprises the information of the one or more beams from the second cell for which the one or more conditions were fulfilled.

[0020] According to a sixteenth aspect, there is provided the access node of any of the thirteenth to fifteenth aspects, further comprising: means for transmitting, to the user device, a response to the leave indication, wherein the response indicates a permission for performing the conditional cell switch procedure from the first cell to the second cell.

[0021] According to a seventeenth aspect, there is provided the access node of the sixteenth aspect, further comprising: means for receiving, from the access node of the second cell, a response message indicating an acknowledgement for receiving the message, wherein the means for transmitting the response to the leave indication are configured to transmit the response to the user device based on receiving the response message from the access node of the second cell.

[0022] According to an eighteenth aspect, there is provided an access node of a second cell, the access node comprising: means for receiving, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; and means for preparing the second cell for the conditional cell switch procedure based on the message.

[0023] According to a nineteenth aspect, there is provided the access node of the eighteenth aspect, further comprising: means for activating uplink resources for the user device on one or more beams from the second cell based on the message, wherein the message comprises information of the one or more beams from the second cell for which one or more conditions related to the conditional cell switch procedure were fulfilled.

[0024] According to a twentieth aspect, there is provided the access node of the eighteenth or nineteenth aspect, wherein the message comprises context information associated with the user device, wherein the means for preparing the second cell are configured to prepare the second cell based on the context information.

[0025] According to a twenty-first aspect, there is provided the access node of the twentieth aspect, further comprising: means for starting a timer based on receiving the message, wherein the timer is set to expire after a pre-defined time period; and means for releasing a configuration associated with the context information based on detecting that the timer has expired.

[0026] According to a twenty-second aspect, there is provided a method comprising: receiving, by a user device, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; determining, by the user device, whether the one or more conditions are fulfilled; and based on determining that the one or more conditions are fulfilled, transmitting, by the user device, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells, wherein the leave indication is transmitted before performing the conditional cell switch procedure.

[0027] According to a twenty-third aspect, there is provided a method comprising: transmitting, by an access node of a first cell, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; receiving, by the access node of the first cell, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells; based on receiving the leave indication, generating, by the access node of the first cell, a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; and transmitting, by the access node of the first cell, the message to the access node of the second cell.

[0028] According to a twenty-fourth aspect, there is provided a method comprising: receiving, by an access node of a second cell, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; and preparing, by the access node of the second cell, the second cell for the conditional cell switch procedure based on the message.

[0029] According to a twenty-fifth aspect, there is provided a computer program comprising instructions which, when executed by a user device, cause the user device to perform at least the following: receiving, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; determining whether the one or more conditions are fulfilled; and based on determining that the one or more conditions are fulfilled, transmitting, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells, wherein the leave indication is transmitted before performing the conditional cell switch procedure.

[0030] According to a twenty-sixth aspect, there is provided a computer program comprising instructions which, when executed by an access node of a first cell, cause the access node to perform at least the following: transmitting, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; receiving, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells; based on receiving the leave indication, generating a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; and transmitting the message to the access node of the second cell.

[0031] According to a twenty-seventh aspect, there is provided a computer program comprising instructions which, when executed by an access node of a second cell, cause the access node to perform at least the following: receiving, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; and preparing the second cell for the conditional cell switch procedure based on the message.

[0032] According to a twenty-eighth aspect, there is provided a non-transitory computer readable medium comprising program instructions which, when executed by a user device, cause the user device to perform at least the following: receiving, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; determining whether the one or more conditions are fulfilled; and based on determining that the one or more conditions are fulfilled, transmitting, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells, wherein the leave indication is transmitted before performing the conditional cell switch procedure.

[0033] According to a twenty-ninth aspect, there is provided a non-transitoiy computer readable medium comprising program instructions which, when executed by an access node of a first cell, cause the access node to perform at least the following: transmitting, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; receiving, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells; based on receiving the leave indication, generating a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; and transmitting the message to the access node of the second cell.

[0034] According to a thirtieth aspect, there is provided a non-transitory computer readable medium comprising program instructions which, when executed by an access node of a second cell, cause the access node to perform at least the following: receiving, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; and preparing the second cell for the conditional cell switch procedure based on the message.

[0035] According to a thirty-first aspect, there is provided a computer readable medium comprising program instructions which, when executed by a user device, cause the user device to perform at least the following: receiving, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; determining whether the one or more conditions are fulfilled; and based on determining that the one or more conditions are fulfilled, transmitting, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells, wherein the leave indication is transmitted before performing the conditional cell switch procedure.

[0036] According to a thirty-second aspect, there is provided a computer readable medium comprising program instructions which, when executed by an access node of a first cell, cause the access node to perform at least the following: transmitting, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; receiving, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells; based on receiving the leave indication, generating a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; and transmitting the message to the access node of the second cell.

[0037] According to a thirty-third aspect, there is provided a computer readable medium comprising program instructions which, when executed by an access node of a second cell, cause the access node to perform at least the following: receiving, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; and preparing the second cell for the conditional cell switch procedure based on the message.

[0038] According to a thirty-fourth aspect, there is provided a user device comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user device at least to: receive, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; determine whether the one or more conditions are fulfilled; and based on determining that the one or more conditions are fulfilled, transmit, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells, wherein the leave indication is transmitted before performing the conditional cell switch procedure.

[0039] According to a thirty-fifth aspect, there is provided an access node of a first cell, the access node comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to: transmit, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure; receive, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells; based on receiving the leave indication, generate a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; and transmit the message to the access node of the second cell.

[0040] According to a thirty-sixth aspect, there is provided an access node of a second cell, the access node comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to: receive, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; and prepare the second cell for the conditional cell switch procedure based on the message. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In the following, various example embodiments will be described in greater detail with reference to the accompanying drawings, in which FIG. 1A illustrates an example of a wireless communication network; FIG. IB illustrates an example of a system; FIG. 2 illustrates a signal flow diagram; FIG. 3A illustrates an example, where a user equipment transmits a leave indication and performs a conditional cell switch procedure without waiting for a response from the network; FIG. 3B illustrates an example, where the user equipment waits for a response from the network in a blocking wait manner; FIG. 3C illustrates an example, where the user equipment waits for a response from the network in a non-blocking wait manner; FIG. 4 illustrates an example of a timer; FIG. 5 illustrates a flow chart; FIG. 6 illustrates a flow chart; FIG. 7 illustrates a flow chart; FIG. 8 illustrates a flow chart; FIG. 9 illustrates a flow chart; FIG. 10 illustrates a flow chart; FIG. 11 illustrates a flow chart; FIG. 12 illustrates a flow chart; FIG. 13 illustrates an example of an apparatus; and FIG. 14 illustrates an example of an apparatus. DETAILED DESCRIPTION

[0042] 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 consistof 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.

[0043] 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): global system for mobile communications (GSM) or any other second generation (2G) radio access technology, universal mobile telecommunication system (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), long term evolution (LTE), LTE-Advanced, fourth generation (4G), fifth generation (5G), 5G new radio (NR), 5G-Advanced (i.e., 3GPP NR Rel-18 and beyond), or sixth generation (6G). 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.

[0044] It should be noted that the embodiments are not restricted to the wireless communication network given as an example, but a person skilled in the art may also apply the solution to other wireless communication networks or systems provided with necessaiy properties. For example, some example embodiments may also be applied to a communication system based on IEEE 802.11 specifications, or a communication system based on IEEE 802.15 specifications. IEEE is an abbreviation for the Institute of Electrical and Electronics Engineers.

[0045] FIG. 1A depicts an example of a simplified wireless communication network showing some physical and logical entities. The connections shown in FIG. 1A 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. 1A.

[0046] 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.

[0047] The example wireless communication network shown in FIG. 1A includes a radio access network (RAN) and a core network 110.

[0048] FIG. 1A 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.

[0049] 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, or a RAN node.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The access node 104 may further be connected to a core network (GN) 110. The core network 110 may comprise an evolved packet core (EPC) network and / or a 5th generation core network (5GC). The EPC may comprise network entities, such as a serving gateway (S-GW for routing and forwarding data packets), a packet data network gateway (P-GW) for providing connectivity of UEs to external packet data networks, and / 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).

[0054] 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.

[0055] 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.

[0056] 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. In this description, the terms "UE” and “user device” may be used interchangeably.

[0057] 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 sensor comprising a wireless modem, or a computing device comprising a wireless modem integrated in a vehicle.

[0058] 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 (loT) network, which is a scenario in which objects may be provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction.

[0059] The wireless communication network may also be able to support the usage of cloud services. For example, at least part of core network operations may be carried out as a cloud service (this is depicted in FIG. 1A by "cloud" 114). The UE 100, 102 may also utilize the cloud 114. In some applications, the computation for a given UE may be carried out in the cloud 114 or in another UE.

[0060] 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.

[0061] 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.

[0062] 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).

[0063] 5G wireless communication networks may also apply network slicing, in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same physical infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

[0064] 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 (LI) 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).

[0065] 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.

[0066] 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.

[0067] 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).

[0068] 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).

[0069] 5G (or new radio, NR) wireless communication networks may support multiple hierarchies, where multi-access edge computing (MEC) servers may be placed between the core network 110 and the access node 104. It should be appreciated that MEC may be applied in LTE wireless communication networks as well.

[0070] 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 (loT) devices or for passengers on board of vehicles, or ensuring service availability for critical 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 mega-constellations (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.

[0071] It is obvious for a person skilled in the art that the access node 104 depicted in FIG. 1A 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.

[0072] 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. 1A 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.

[0073] For fulfilling the need for improving performance of radio access networks, the concept of “plug-and-play” access nodes may be introduced. A radio access network, which may be able to use “plug-and-play” access nodes, may include, in addition to Home eNodeBs or Home gNodeBs, a Home Node B gateway (HNB-GW) (not shown in FIG. 1A). An HNB-GW, which may be installed within an operator’s radio access network, may aggregate traffic from a large number of Home eNodeBs or Home gNodeBs back to a core network 110 of the operator.

[0074] 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 by mobile 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.

[0075] FIG. IB illustrates an example of a system, to which some example embodiments may be applied. FIG. IB may be understood to depict a part of the wireless communication network of FIG. 1A, but with greater accuracy with respect to a mobility scenario.

[0076] The system comprises at least a UE 100 and a plurality of access nodes 104,104B, 104C, 104D controlling a plurality of cells 121,122,123,124. Herein the term “cell” refers to a radio cell. Although four cells 121, 122,123,124 and four access nodes 104,104B, 104C, 104D are shown in FIG. IB, it should be noted that the number of cells and access nodes may also be higher or lower than four.

[0077] Moreover, in FIG. IB, each of the cells is managed by a separate access node. However, it should be noted that one access node (e.g., 104,104B, 104C, or 104D) may manage or control one or more cells 121,122,123,124.

[0078] Referring to FIG. IB, during a cell switch (or handover), the connection of the UE 100 is transferred from the current serving cell (e.g., source cell) 121 controlled by a source access node 104 to a target cell 122 controlled by a target access node 104B, while preserving the ongoing voice call or data session.

[0079] The cell switch procedure may be initiated by the network (e.g., the source access node 104), when certain pre-defined conditions are met, such as when the signal quality of the current serving cell 121 falls below a specified threshold, or when the signal quality of the neighboring cell 122 becomes better than that of the current serving cell 121 by a pre-defined offset. The decision to perform a cell switch may be based on various factors, including radio measurements such as reference signal received power (RSRP) and / or reference signal received quality (RSRQ), network load, UE mobility, and network configuration parameters.

[0080] Upon initiation of the cell switch procedure, the network (e.g., the source access node 104) may transmit a configuration message to the UE 100. This configuration message may include information about the target cell 122 and any needed configuration parameters. The UE 100 may then establish a connection with the target access node 104B controlling the target cell 122, synchronize its timing and frequency, and exchange control information to confirm the successful completion of the cell switch. Once the cell switch is completed, the UE 100 releases its connection with the previous serving cell 121, and the communication continues through the new serving cell 122.

[0081] The handover may be an intra-radio-access-technology (intra-RAT) handover or an inter-radio-access-technology (inter-RAT) handover. The cell switch may also be an intra-frequency cell switch or an inter-frequency cell switch.

[0082] An intra-RAT handover means that the source cell 121 and the target cell 122 are based on the same radio access technology. For example, in an intra-NR handover, both the source access node 104 and the target access node 104B may be gNBs (i.e., NR base stations).

[0083] An inter-RAT handover means that the source cell 121 and the target cell 122 are based on different radio access technologies. For example, in an inter-RAT handover, the source access node 104 may be an eNB or ng-eNB (i.e., 4G base station), and the target access node 104B may be a gNB (i.e., NR base station), or vice versa.

[0084] There are various types of handover procedures. For example, a conditional handover (CHO) may be defined as a handover that is executed by the UE 100, when one or more handover execution conditions are met. In other words, the UE 100 receives (e.g., from the source access node 104) a configuration message with a CHO configuration indicating one or more handover execution conditions, but the UE 100 does not execute the handover until the one or more handover execution conditions are met. The UE 100 may start evaluating the one or more handover execution conditions upon receiving the CHO configuration, and stop evaluating the one or more handover execution conditions once a handover is executed.

[0085] An advantage of CHO is that it improves the mobility robustness compared to legacy handover by reducing the number of radio link failures and handover failures. This is achieved by de-coupling the handover execution phase from the preparation phase, thus enabling the UE 100 to receive the configuration message early, when the radio link of the source cell 121 is still sufficient, and executing the handover later when the radio link of the target cell 122 is strong enough.

[0086] The CHO configuration may be included in an RRC reconfiguration message, for example. The CHO configuration comprises the configuration of CHO candidate cell(s) 122, 123, 124 generated by the candidate target access node(s) 104B, 104C, 104D, and the one or more handover execution conditions generated by the source access node 104. The one or more handover execution conditions may comprise, for example CHO event A3 and / or CHO event A5. One or more reference signal types maybe supported and one or more trigger quantities may be configured for the evaluation of the CHO execution condition of a given candidate cell 122, 123, 124. The one or more trigger quantities may comprise, for example, reference signal received power (RSRP), reference signal received quality (RSRQ), and / or signal-to-interference-plus-noise ratio (S1NR).

[0087] CHO event A3 means that a trigger quantity (e.g., RSRP, RSRQ, and / or SINR) of a CHO candidate cell 122 indicated in the CHO configuration exceeds the trigger quantity (e.g., RSRP, RSRQ, and / or SINR) of the source cell 121 by an offset for a certain time-to-trigger (TTT) period.

[0088] CHO event A5 means that the trigger quantity of the source cell 121 becomes lower than a first threshold, and the trigger quantity of a CHO candidate cell 122 indicated in the CHO configuration exceeds a second threshold for a certain TTT period.

[0089] Before any CHO execution condition is satisfied, upon reception of a handover command (without CHO configuration) or L1 / L2 triggered mobility (LTM) cell switch command MAC control element (CE), the UE 100 may execute the handover procedure or LTM cell switch procedure, regardless of any previously received CHO configuration.

[0090] While executing the CHO (i.e., from the time when the UE 100 starts synchronization with the target cell 122), the UE 100 may not monitor the source cell

[0091] CHO may also be supported for the integrated access and backhaul (1AB) mobile terminated (MT) in context of intra- and inter-donor IAB node migration and backhaul radio link failure recovery.

[0092] LTM cell switch is a procedure in which an access node 104 (e.g., gNB) receives L3 or LI measurement report(s) from a UE 100, and on their basis the access node 104 changes the UE’s serving cell by a cell switch command signalled via a MAC CE, for example. The cell switch command indicates an LTM candidate configuration that the access node 104 previously prepared and provided to the UE 100 through RRC signalling. Then the UE 100 switches to the target configuration according to the cell switch command. The LTM cell switch procedure can be used to reduce the mobility latency.

[0093] When configured by the network (e.g., the access node 104), it is possible to activate transmission configuration indicator (TCI) states of one or multiple cells 122,123,124 that are different from the current serving cell 121. For instance, the TCI states of the LTM candidate cells 122, 123,124 can be activated in advance before any of those cells become the serving cell of the UE 100. This allows the UE 100 to be downlink-synchronized with those cells 122, 123, 124, thereby facilitating a faster cell switch to one of those cells when the cell switch is triggered.

[0094] When configured by the network (e.g., the access node 104), it is possible to initiate an uplink timing advance (TA) acquisition (called early TA) procedure of one or multiple cells 122,123,124 that are different from the current serving cell(s) 121. If the cell has the same timing advance value (Nta) as the current serving cell(s) or Nta=0, the early TA acquisition procedure is not required. The network may request the UE 100 to perform early TA acquisition of a candidate cell 122, 123, 124 before a cell switch. The early TA acquisition procedure may be triggered by a physical downlink control channel (PDCCH) order or realized through UE-based TA measurement as configured by RRC. In the former case, the access node or DU to which the candidate cell belongs may calculate the TA value and transmit it to the source access node 104 or DU 105 to which the serving cell 121 belongs via the CU 108. The serving cell 121 may transmit the TA value in the LTM cell switch command MAC CE, when triggering the LTM cell switch. In the latter case, the UE 100 may perform TA measurement for the candidate cells 122, 123, 124 after being configured by RRC, but the exact time when the UE 100 performs TA measurement may be up to UE implementation. The UE 100 applies the TA value measured by itself and performs RACH-less LTM upon receiving the cell switch command (RACH is an abbreviation for random access channel). The network (e.g., the source access node 104) may also send a TA value in the LTM cell switch command MAC CE without early TA acquisition.

[0095] Depending on the availability of a valid TA value, the UE 100 may perform either a RACH-less LTM or RACH-based LTM cell switch. If the valid TA value is provided in the cell switch command, the UE 100 may apply the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no valid TA value is provided in the cell switch command, the UE 100 may apply the valid TA value by itself, if available. Meanwhile, the UE 100 may perform a RACH-less LTM cell switch upon receiving the cell switch command. If no valid TA value is available, the UE 100 may perform a RACH-based LTM cell switch.

[0096] Regardless of whether the UE 100 is configured for UE-based TA measurement for a certain candidate cell, it will still follow the PDCCH order, which includes requesting a random-access procedure towards the candidate cells 122, 123, 124. This also applies to the candidate cells for which the UE 100 is capable of deriving TA values by itself. Additionally, regardless of whether the UE 100 has already performed a random-access procedure towards the candidate cells 122,123,124, it will still follow the UE-based measurement configuration, if configured by the network.

[0097] For RACH-less LTM, the UE 100 may access the target cell 122 using either a configured grant or a dynamic grant. The configured grant may be provided in the LTM candidate configuration, and the UE 100 may select the configured grant occasion associated with the beam indicated in the cell switch command. Upon initiation of LTM cell switch to the target cell 122, the UE 100 starts to monitor PDCCH on the target cell 122 for dynamic scheduling. Before RACH-less LTM procedure completion, the UE 100 may not trigger a random-access procedure, if it does not have a valid physical uplink control channel (PUCCH) resource for triggered scheduling requests (SRs).

[0098] The following principles apply to LTM: 1) security keys are maintained upon an LTM cell switch; and 2) subsequent LTM is supported.

[0099] LTM supports both intra-gNB-DU and intra-gNB-CU inter-gNB-DU mobility. LTM supports both intra-frequency and inter-frequency mobility, including mobility to an inter-frequency cell that is not a current serving cell. LTM is supported for licensed spectrum. The following scenarios are supported: primary cell (PCell) change in non-carrier-aggregation scenario and non-dual-connectivity scenario; PCell and secondary cell (SCell) change in a carrier aggregation scenario; dual connectivity scenario: including PCell and master cell group (MCG) SCell(s) change and intra-secondary-node PSCell and secondary cell group (SCG) SCell(s) change without master node (MN) involvement.

[0100] While the UE 100 has stored LTM candidate configurations, the UE 100 can also execute any L3 handover except for dual active protocol stack (DAPS) handover.

[0101] The cell switch command may be conveyed in a MAC CE, which contains the necessary information to perform the LTM cell switch.

[0102] The procedure for LTM is as follows. In a first step, the UE 100 transmits a MeasurementReport message to the source access node 104. The source access node 104 decides to configure LTM and initiates LTM preparation.

[0103] In a second step, the source access node 104 transmits an RRCReconfiguration message to the UE 100 including the LTM candidate configurations.

[0104] In a third step, the UE 100 stores the LTM candidate configurations and transmits an RRCReconfigurationComplete message to the source access node 104.

[0105] In a fourth step, the UE 100 performs DL synchronization with the LTM candidate cell(s) 122,123,124 before receiving the cell switch command. The UE 100 may activate and deactivate TCI states of LTM candidate cell(s) 122, 123, 124, as triggered by the source access node 104.

[0106] The UE 100 may perform UL synchronization with LTM candidate cell(s) 122, 123, 124 before receiving the cell switch command, by using UE-based TA measurement, if configured, and / or by transmitting a RACH preamble towards the candidate cell, as triggered by the source access node 104. When UE-based TA measurement is configured, the UE 100 acquires the TA value(s) of the candidate cell(s) 122, 123, 124 by measurement. The UE 100 performs early TA acquisition with the candidate cell(s) 122,123,124 as requested by the network (e.g., the source access node 104) before receiving the cell switch command. This may be done via contention-free random access (CFRA) triggered by a PDCCH order from the source cell 121, following which the UE 100 transmits a RACH preamble towards the indicated candidate cell. In order to minimize the data interruption of the source cell 121 due to CFRA towards the candidate cell(s) 122,123,124, the UE 100 may not receive a random-access response from the network for the purpose of TA value acquisition, and the TA value of the candidate cell is indicated in the cell switch command. The UE 100 may not maintain the TA timer for the candidate cell and relies on network implementation to guarantee the TA validity.

[0107] In a fifth step, the UE 100 performs LI measurements on the configured LTM candidate cell(s) 122, 123,124 and transmits LI measurement reports to the source access node 104. LI measurement should be performed as long as the RRC reconfiguration from the second step is applicable.

[0108] In a sixth step, the source access node 104 decides to execute a cell switch to a target cell 122 and transmits, to the UE 100, an LTM cell switch command MAC CE triggering cell switch by including a target configuration identifier, which indicates the index of the candidate configuration of the target cell 122, a beam indicated with a TCI state or beams indicated with DL and UL TCI states, and a timing advance command for the target cell 122, if available. The UE 100 switches to the target cell 122 and applies the candidate configuration indicated by the target configuration identifier.

[0109] In a seventh step, the UE 100 performs the random-access procedure towards the target cell 122, if the UE 100 does not have valid TA of the target cell 122.

[0110] In an eighth step, the UE 100 completes the LTM cell switch procedure by transmitting an RRCReconfigurationComplete message to the target cell 122. If the UE 100 has performed a random-access procedure in step 7, the UE 100 considers that the LTM cell switch execution is successfully completed, when the random-access procedure is successfully completed. For RACH-less LTM, the UE 100 considers that LTM cell switch execution is successfully completed, when the UE 100 determines that the network has successfully received its first UL data.

[0111] The steps 4 to 8 can be performed multiple times for subsequent LTM cell switch executions using the LTM candidate configuration's) provided in step 2.

[0112] In other words, subsequent LTM is done by repeating the early synchronization, LTM cell switch execution, and LTM cell switch completion steps without releasing other LTM candidate configurations after each LTM cell switch completion.

[0113] After receiving an LTM cell switch command MAC CE, the UE 100 performs MAC reset. Whether the UE 100 performs radio link control (RLC) re establishment and PDCP data recovery during cell switch may be explicitly controlled by the network through RRC signalling.

[0114] LTM was introduced in NR Release 18 and can offer improvements in handover latency and interruption time compared to Layer 3 based mobility. However, LTM as introduced in NR Release 18 also has a number of limitations compared to Layer 3 mobility.

[0115] Currently, LTM operation is only supported for mobility between cells of the same gNB (same CU). Depending on the deployment of the network, this may significantly limit the opportunities to use LTM. By enabling LTM operation between cells of different gNBs (i.e., inter-CU), the network may be able gain the benefits of LTM for a far greater number of handovers.

[0116] Layer 3 mobility uses layer 3 measurement reporting, which supports UE-evaluated events for triggering of measurement reports and reduces signalling overhead compared to periodic measurement reporting. Such event triggering is not supported by the LI measurements that are used for LTM mobility.

[0117] LI measurements for LTM procedures may comprise synchronization signal block (SSB) measurements. Expanding LI measurements to include channel state information reference signal (CSI-RS) measurements may address this limitation and can be expected to enable greater throughput on the target cell immediately after cell switch.

[0118] Layer 3 mobility has evolved over several releases. Conditional handover (CHO) and other conditional mobility procedures, such as conditional primary secondary cell (PSCell) addition and change (CPAC) and subsequent conditional PSCell addition and change (SCPAC), were developed to achieve high robustness by enabling the procedure to be executed without necessitating a signalling exchange with the source cell beforehand. LTM as introduced in NR Release 18 offers short interruption time, but not with the same level of robustness as the conditional L3 mobility procedures. In NR Release 19, enhancements should be specified so that the system can benefit from both the high robustness and short interruption.

[0119] On the network side, one of the challenges in conditional handover is the timely preparation of the target cell. Prior to transferring the UE from one cell to another via a cell switch or a handover, various actions need to occur on the network side.

[0120] For instance, the UE context needs to be transferred from one gNB or CU to another gNB or CU before or after triggering the UE transfer. Furthermore, depending on whether the UE is in active data transmission, data packets need to be transmitted from the source cell to the target cell during the interruption time.

[0121] When the network is in control of the handover execution, it can be controlled by the network when to initiate data forwarding etc. In conditional handovers, the UE is allowed to switch the cell autonomously based on the configuration from the network. The UE starts the handover autonomously based on the configuration, once the configured condition is met, and evaluated by the UE. Therefore, the network has very little control on exactly when the handover is executed by the UE, other than the event configuration. When the UE is at the cell edge, the CHO-style handover may work well. However, when LTM is being used, the handover or cell switch may likely occur while the UE is actively transmitting data, and the UE may be in good radio conditions. Hence, the UE is not necessarily configured to trigger the handover or cell switch at the cell edge, and low interruption time matters.

[0122] An additional issue with the current conditional mobility procedures is that if the network has configured the UE with more than one target CHO cell, the network does not even know which particular target cell the UE will enter, and when the UE could enter the particular target cell.

[0123] For example, if the network configures 8 candidate cells for LTM cell switch to the UE, the network may need to also preconfigure the UE context for these 8 candidate cells for conditional LTM. Additionally, for all the candidate cells, the network may need to reserve some uplink resources (i.e., configured grant) for the UE for RACH-less cell switch. These aspects make the conditional LTM cell switch with multiple target cells inefficient from the network point of view.

[0124] To address the above issues, some example embodiments provide a UE leave indication and associated procedures to add control to the conditional LTM cell switch (or any other conditional cell switch or handover procedure). This leave indication indicates to the network, upon meeting a configured trigger condition, that the UE 100 is about to perform a conditional cell switch (e.g., conditional LTM cell switch). Hence, the leave indication indicates that the UE 100 is leaving the source cell 121 and transferring to another cell 122, due to a conditional cell switch.

[0125] When the configured trigger condition (e.g., a conditional event or a specific leave indication event) is met, for instance UE observed signal level has changed and the UE has evaluated the condition, for instance by performing measurements, the UE 100 transmits a leave indication to the network which may indicate the target cell identity, for example a candidate identifier (i.e., candidateld), or a value derived from the candidateld (e.g., a temporary identifier), or an indication of a measurement resource associated with the beam or the cell where the condition was met.

[0126] The leave indication may also provide information about the fulfilled condition (e.g., condition reference).

[0127] The leave indication may be triggered immediately after the configured condition(s) is met, and the UE observes the signal change, or after the UE has had time to perform at least one procedure such as measurement period including at least one reference signal measurement. Alternatively, or additionally, the at least one procedure may include processing associated with the Trrc-processingdelay component, such as ASN.l message validation and decoding for the cell(s) that the condition(s) are met.

[0128] The leave indication may also provide information of the selected DL beam (TCI state(s)) from the target cell 122, for example for RACH-less cell switch. The DL beam information may be used by the target cell 122 to activate or use the correct DL SSB or beam direction for scheduling the UE 100 with UL transmission and / or DL reception when it accesses the target cell 122. The SSB or beam information may be used by the target cell 122 to activate the appropriate configured grant (i.e., associated with the selected beam).

[0129] In case of RACH-less cell switch (when the TA of the target cell 122 has been provided in the LTM cell switch command or acquired autonomously by the UE 100), another benefit of the leave indication is to enable the target cell 122 to activate the configured UL grant(s) for the UE 100 to transmit the first uplink message.

[0130] Upon receiving the leave indication, the network may prepare the indicated target cell 122 in a “just-in-time” manner instead of being required to use early preparation procedures. The network may also split the processing in two. For example, the network may firstly store the configuration received in the previous message transfer, and then the network may activate the configuration for the indicated UE after the indication is received. The network may also trigger just-in-time data transfer from the source cell 121 to the target cell 122.

[0131] Thus, a benefit of the leave indication is that instead of preparing a large number of candidate cells 122,123,124 in advance, the network may perform just-in-time preparation of a single target cell 122. The preparation time on the network side may be the same as the time that the UE 100 is required to wait when a leaveTimer is configured (i.e., the preparation may occur while the leaveTimer is running). The preparation may still comprise two phases on the network side (e.g., UE context may be transmitted, but the target cell does not apply the configuration before the preparation triggered by the leave indication). The preparation phase may also include the target cell acquiring necessary access control information from the core network entities.

[0132] The leave indication may optionally also comprise the status of TA acquisition with the target cell 122. For example, in case of UE-based TA, the network may not know if TA has been acquired or not. The leave indication may indicate whether or not the UE 100 has a valid TA with the target cell 122. This may help the target cell 122 to know whether the cell switch will be RACH-based (i.e., including a random-access procedure) or RACH-less (i.e., not including a random-access procedure).

[0133] 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.

[0134] FIG. 2 illustrates a signal flow diagram according to an example embodiment.

[0135] Referring to FIG. 2, at 201, a UE 100 may transmit data to an access node (e.g., a source access node) 104 of a first cell 121 (source cell), and / or receive data from the access node 104 of the first cell 121. The first cell 121 may refer to the current serving cell of the UE 100 (i.e., the source cell of the cell switch procedure).

[0136] At 202, the UE 100 may transmit an L3 measurement report to the access node 104 of the first cell 121.

[0137] At 203, the access node 104 of the first cell 121 decides or determines to configure a conditional cell switch procedure to the UE 100. The conditional cell switch procedure may refer to, for example, a conditional LTM cell switch or any other type of conditional (e.g., UE initiated) cell switch or handover.

[0138] At 204, based on the decision of 203, the access node 104 of the first cell 121 transmits an early configuration to a target access node 104B of a second cell 122 (i.e., target cell of the cell switch procedure).

[0139] For example, the early configuration may comprise partial or full context information associated with the UE 100. The context information refers to the set of parameters and configurations associated with a specific UE, ensuring effective communication and service quality. The context information may comprise, for example, at least one of: radio resource settings, security measures, and / or mobility data.

[0140] Herein the terms "first cell” and "second cell” are used to distinguish the cells, and they do not necessarily refer to any specific order or specific identifiers of the cells.

[0141] At 205, the target access node 104B stores the early configuration. This early configuration may be only partially processed by the target access node 104B. In other words, the second cell 122 may only perform minimum processing of the early configuration to save resources.

[0142] For example, the target access node 104B may store the partial or full context information, so that it does not require runtime resources. The target access node 104B may also perform some pre-processing of the early configuration.

[0143] At 206, the access node 104 of the first cell 121 transmits, to the UE 100, configuration information related to the conditional cell switch procedure. The configuration information indicates one or more conditions and one or more candidate cells 122,123,124 for the conditional cell switch procedure. The one or more candidate cells 122,123,124 comprise at least the second cell 122 and possibly one or more other cells 123,124. The UE 100 receives the configuration information from the source access node 104.

[0144] The configuration information may also indicate a time duration for a timer (e.g., called leaveTimer), which indicates how long the UE 100 needs to wait for a response from the access node 104 after transmitting the leave indication.

[0145] The configuration information of 206 may be transmitted in an RRCReconfiguration message, for example.

[0146] At 207, the UE 100 transmits, for example, an RRCReconfiguration complete message (or another type of acknowledgement) to indicate that the configuration information was successfully received.

[0147] At 208, the UE 100 evaluates the one or more conditions to determine whether the one or more conditions are fulfilled. The UE 100 may perform one or more radio measurements associated with the one or more conditions on at least the second cell 122 for evaluating the one or more conditions.

[0148] As an example, the one or more conditions may comprise a component representing a process or a time that the UE has from a point where the configured event, for example: neighbouring cell or beam(s) become better than a threshold, serving cell or beam(s) becomes worse than a threshold, neighbour cell or beam(s] becomes better than serving cell or beam(s) by an offset, or neighbour cell or beam(s] becomes better than a threshold. The event may also consider a side condition or a threshold when the event is applied. There may be a component that describes the time when the event occurs at the measurement reference point, for instance when the signal level is such that the event is triggered, and a component when the UE evaluates or realizes that the event was occurring at the measurement reference point. The time of the signal change can be reflected with a component, such as Tltm- event_condition, and the realisation of the event on the UE side may be reflected with another component, such as Tltm-event-condition-realisation- The event realisation may be defined as or contain a measurement component to evaluate whether the event condition is met with at least one measurement, or a measurement period. The component may be described with a measurement period component such as Tmeasureto evaluate that the condition was met.

[0149] At 209, based on the evaluation, the UE 100 determines that the one or more conditions are fulfilled at least for the second cell 122.

[0150] At 210, based on determining that the one or more conditions are fulfilled, the UE 100 generates and transmits, to the access node 104 of the first cell 121, a leave indication indicating that the UE 100 intends to perform the conditional cell switch procedure from the first cell 121 to the second cell 122 comprised in the one or more candidate cells 122, 123, 124. For example, when a condition exists at the measurement reference point which will trigger UE to evaluate the event condition, and the conditional event (e.g., LTM-event-condition, TLTM-event-condition-reaiisation or Tevent_Du), the UE 100 transmits the leave indication to the access node 104 of the first cell 121. The leave indication is transmitted before performing the conditional cell switch procedure (e.g. before UE is performing RACH procedure or first data transmission to the target cell) to switch to the target cell where the condition was met. From the time where the event was met, the UE may perform other actions prior to transmitting the leave indication, for instance performing a measurement period (e.g., Tmeasure] for the cell or beam associated with the condition. The access node 104 of the first cell 121 receives the leave indication.

[0151] The leave indication may comprise at least one of: an identifier of at least the second cell 122 for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell 122, information of one or more downlink beams from the second cell 122 for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell 122.

[0152] The leave indication may comprise an identifier of a single target cell (i.e., the second cell 122), or it may comprise identifiers of multiple target cells 122,123, 124 (e.g., all the candidate cells for which the one or more conditions were fulfilled). In case the leave indication comprises identifiers of multiple target cells 122,123,124, the network (e.g., the access node 104) may select one or more target cells based on the measurement results. For example, the network may select the target cell (e.g., the second cell 122) with the strongest measured signal strength or quality.

[0153] As an example, the leave indication may be transmitted in a MAC CE message comprising an identifier of at least the cell(s) (e.g., the second cell 122) for which the one or more conditions were fulfilled at the measurement instance (e.g., candidateld or a value derived from the candidateld). Alternatively, or additionally, the MAC CE message may indicate the beam(s) for which the one or more conditions were fulfilled at the measurement instance (e.g., reference signal identifier or TCI state identifier). The leave indication may also comprise information of which event was triggered (e.g., if the same candidate cell or beam was configured with multiple conditions). The leave indication may also comprise measurement results associated with the event condition (e.g., RSRP level before or after a measurement period). For instance, the leave indication may be a MAC CE with measurement results including measurement information about the condition being met, or a MAC CE without measurement results but with the condition associated identifiers.

[0154] As another example, the leave indication may be transmitted in an RRC message or ASN.l short message (e.g., below PDCP layer) comprising an identifier of at least the cell(s) (e.g., the second cell 122) for which the one or more conditions were fulfilled at the measurement instance. Alternatively, or additionally, the RRC message may indicate the beam(s) for which the one or more conditions were fulfilled at the measurement instance (e.g., reference signal identifier or TCI state identifier). The leave indication may also comprise information of which event was triggered (e.g., if the same candidate cell or beam was configured with multiple conditions).

[0155] As another example, the leave indication may be explicitly signalled in a measurement report comprising at least the identifier (e.g., candidateld) of the second cell 122 (e.g., a bit field or enum in an RRC field associated with the candidateld). The measurement report may be an LI measurement report or an L3 measurement report or an event-triggered measurement report, for example.

[0156] The leave indication may be a special format measurement report. For example, the leave indication may be a measurement report which comprises only the measurement associated with the condition(s) that were met. For instance, if one condition for one cell was met, the UE 100 may not transmit a full set of measurements (e.g., in LI report 4), but the UE 100 may transmit one value and the UE 100 may mark other values to a special value (e.g. 0, FFF, or invalid value, unmeasured value).

[0157] The LI measurement report may comprise a flag which indicates for which reference signal identifier the one or more conditions were fulfilled at the measurement instance. The reference signal identifier can be mapped to the candidate cell (e.g., the second cell 122) and / or TCI state.

[0158] The L3 measurement report may comprise a flag indicating which cell(s) or beam(s) the one or more conditions were fulfilled at the measurement instance. Alternatively, or additionally, the L3 measurement report may comprise a bitmap of the configured candidate cell(s) or beam(s), which indicates the candidate cells or beams where the one or more conditions were fulfilled at the measurement instance.

[0159] The leave indication may be an event-triggered measurement report, which is transmitted once the one or more conditions are fulfilled met, and the UE 100 may have performed at least one measurement period. The event-triggered measurement report (LI or L3) may comprise A + B amount of candidate cell and / or beam reports configured for conditional LTM, where A is the number of cells or beams where the one or more conditions were fulfilled (included together with the associated measurement results), and B is the number of measurement results of other candidate cells or beams configured to be included in the measurement report (for which the one or more conditions were not fulfilled). The report may be ordered to have the cell or beam where the one or more conditions were triggered as a first cell or beam, followed by the cell(s) or beam(s) where the one or more conditions were not fulfilled. The fulfilment or triggering of the one or more conditions may be indicated, for example, with a MAC CE bit field (e.g., before or after the candidateld). As another example, there may be a bitmap which indicates a value of 1 if the one or more conditions were fulfilled, and a value of 0 if the one or more conditions were not fulfilled (e.g., 8 cells = 8 bits).

[0160] In one embodiment, the leave indication may be transmitted after the UE 100 has performed measurements which are required to meet the accuracy requirements. The measurements may comprise LI measurements and / or L3 measurements. For example, the UE 100 may perform at least one of: CS1-RS based measurements, SSB based measurements, or primary synchronization signal (PSS) and / or secondary synchronization signal (SSS) based measurements with a specified number of samples. In this case, the leave indication may be transmitted, for example, in a measurement report for reporting the one or more radio measurements, based on obtaining a pre-defined number of measurement samples from the one or more radio measurements.

[0161] In one embodiment, the UE 100 may not transmit the measurement report after conditional LTM cell switch is configured until the condition exists at the measurement reference point (i.e., the one or more conditions are fulfilled), and the UE 100 has measured the second cell 122 (target cell), i.e., Tevent_du (or it could be LTM-event-condition) + Traeasure has passed. Thus, the network (e.g., the access node 104) knows that the UE 100 has met the event condition, and this acts as a leave indication to the network, and the network proceeds to perform fast target cell preparation.

[0162] TeVent_du is the delay uncertainty which is the time from when the UE 100 successfully decodes a conditional cell switch command (i.e., the configuration information of 206) until a condition exists at the measurement reference point which will trigger the conditional cell switch (i.e., until the one or more conditions are fulfilled).

[0163] Tmeasure means a time period during which the UE 100 has time to perform measurements that fulfil the accuracy requirement to evaluate the signal from the second cell 122 in such a way that it can be reported (if a measurement report would be sent).

[0164] At 211, the UE 100 starts the timer (e.g., called leaveTimer) that is set to expire after the pre-defined time duration indicated in the configuration information (see FIG. 4 for an illustration of the leaveTimer).

[0165] The purpose of this timer is to provide enough time for the network to prepare for the UE 100 entering the target cell 122. In some cases, the network preparation can be guaranteed to be fast (e.g., less than UE conditional cell switch processing time + RACH uncertainties). The network may configure the timer based on the known backhaul and processing delay. For instance, it may be configurable in the order of milliseconds. If the timer is shorter than the UE processing delay, the UE 100 may ignore the timer.

[0166] The timer may be started based on transmitting the leave indication. For example, the timer may be started when the one or more conditions are fulfilled, or when the measurements are completed for fulfilling the accuracy requirement.

[0167] The UE 100 may be required to wait for this pre-defined time duration before proceeding to perform the measurements during Tmeasure# Tltm-processing# or processing associated with early TCI state activation, or before entering the interruption time (Tinterrupt) in the conditional LTM cell switch, or before transmitting the RACH preamble and / or first data to the second cell 122.

[0168] The interruption time refers to the time when the UE 100 is not able to transmit or receive data to or from the network because of the change of the cell. Tltm-processing is the time for UE processing.

[0169] Upon expiration of the timer, the UE 100 may be configured to either cancel the conditional cell switch procedure or proceed with the cell switch without expecting any separate indication or response from the network. In case the UE 100 proceeds with the cell switch, the target cell 122 may reject the first RACH transmission, and the UE 100 may follow the RACH retransmission procedure.

[0170] Depending on radio conditions, different behaviour may occur when the timer expires. The timer behaviour may be associated, for instance with the A events such as the A3 and / or A5 event described above, or LTM events such as LTM2, LTM3, LTM4 and / or LTM5. Event LTM2 means that the beam of the serving cell 121 becomes worse than an absolute threshold. Event LTM3 means that the beam of a candidate cell (e.g., the second cell 122) becomes better than the beam of the serving cell 121 by a certain offset. Event LTM4 means that the beam of a candidate cell (e.g., the second cell 122) becomes better than an absolute threshold. Event LTM5 means that the beam of the serving cell 121 becomes worse than a first absolute threshold, and the beam of a candidate cell (e.g., the second cell 122) becomes better than a second absolute threshold.

[0171] For example, upon expiration of the timer, the UE 100 may be required to perform one of: 1) transmit another measurement report (e.g., if the serving cell 121 and the target cell 122 are in good radio conditions, i.e., above a threshold), 2) not proceed with the cell switch to the target cell 122 (if the serving cell 121 is good enough, e.g., the radio conditions in the serving cell 121 are above a threshold), or 3) proceed with the cell switch to the target cell 122 (if the serving cell 121 is bad enough, e.g., the radio conditions in the serving cell 121 are below a threshold).

[0172] At 212, the access node 104 of the first cell 121 may optionally process the received leave indication, for instance process information such as measurements from the leave indication or the event information. Alternatively, the access node 104 may forward the leave indication transparently without processing as a standalone message, or in an inter-node message container for example, in a handover request message, or in another inter-node message defined in 3GPP TS 38.423.

[0173] At 213, based on receiving the leave indication, the access node 104 of the first cell 121 generates and transmits a message to the target access node 104B, wherein the message indicates that the UE 100 intends to perform the conditional cell switch procedure. In other words, the message may comprise the leave indication received from the UE 100 (with or without processing).

[0174] The message of 213 may further comprise partial or full context information associated with the UE 100.

[0175] In some cases, this message of 213 may be a small activation message indicating the target cell 122 to use a specific UE configuration. For example, the message may comprise an identifier of the UE 100, which refers to the stored early configuration, for instance, candidateld or similar. In other words, the small activation message may comprise only the necessary information to identify the UE 100 for the random-access procedure. The rest of the UE configuration may be stored at 205 in the memory of the target access node 104B (but not applied yet).

[0176] Based on or upon receiving the message, the target access node 104B may start a timer that is set to expire after a pre-defined time period, and release (e.g., via UE context release message) or delete the UE configuration including parameters that allows the network and UE to establish a connection. For instance, the UE configuration may comprise temporary identifiers, bearer configurations and other higher layer parameters. The parameters that are removed may be UE specific and associated with the UE context information based on detecting that the timer has expired. This may be done so that the network does not need to maintain unnecessary configurations for the particular UE.

[0177] In case the leave indication received from the UE 100 comprises information of one or more beams from the second cell 122 for which the one or more conditions were fulfilled, then the message of 213 transmitted to the target access node 104B may comprise the information of the one or more beams from the second cell 122 for which the one or more conditions were fulfilled.

[0178] At 214, the target access node 104B prepares the second cell 122 for the conditional cell switch procedure based on the message. For example, the target access node may prepare the second cell 122 based on the UE context information comprised in the message, and / or based on the stored early configuration. The preparation of the second cell 122 may mean, for example, that the target access node 104B allocates radio resources for the UE 100 on the second cell 122.

[0179] At 215, in case the message comprises information of the one or more beams from the second cell 122 for which one or more conditions related to the conditional cell switch procedure were fulfilled, the target access node 104B may activate uplink resources for the UE 100 on the one or more beams from the second cell 122 based on the message (e.g., in case of RACH-less configured grant based cell switch).

[0180] For example, the UE 100 may be provided uplink resources (e.g., configured grant(s)) to transmit an RRCReconfigurationComplete message for finalizing the cell switch procedure. In some cases, the UE 100 may skip the RRCReconfigurationComplete transmission occasions before it receives a confirmation, which may be a special message such as downlink control information (DC1) including a flag set to true, or MAC CE response from the source cell 121 to proceed with the conditional cell switch procedure.

[0181] At 216, the target access node 104B may transmit, to the access node 104 of the first cell 121, a response message indicating an acknowledgement for receiving the message of 213.

[0182] At 217, the UE 100 may optionally wait for a response to the leave indication from the access node 104 of the first cell 121 before proceeding the initiate the conditional cell switch procedure. The UE 100 may wait for the response in a blocking wait manner (see FIG. 3B) or in a non-blocking wait manner (see FIG. 3C).

[0183] In blocking wait, the UE 100 stops the execution flow of the conditional cell switch and waits until the network provides a permission to continue the procedure towards entering the target cell (i.e., the second cell 122). In other words, in blocking wait, the UE 100 refrains from initiating the conditional cell switch until it receives the response from the network. The UE 100 performs the conditional cell switch procedure based on receiving the response from the access node 104 of the first cell 121.

[0184] In non-blocking wait, the UE 100 proceeds with the execution flow of the conditional cell switch procedure to a pre-defined point, but waits for the response (or until the timer expires) at the pre-defined point before proceeding with the final execution of the cell switch (i.e., before proceeding to enter the second cell 122). In other words, the UE 100 initiates the conditional cell switch procedure based on transmitting the leave indication, stops the conditional cell switch procedure at a pre-defined point, and continues the conditional cell switch procedure from the pre-defined point based on receiving the response to the leave indication from the access node 104 of the first cell 121.

[0185] For example, the pre-defined point in non-blocking wait may mean that the UE 100 proceeds with executing the conditional cell switch procedure until the UE 100 is ready to transmit the RACH preamble to the target access node 104B of the second cell 122 (target cell). The UE 100 may miss or skip some RACH transmission occasions before it receives the response from the access node 104 of the first cell 121 to confirm that the UE 100 can enter the second cell 122. The UE 100 may maintain the fine-time tracking (to maintain the timing in such a way that it meets the uplink timing requirements) while the timer (e.g., leaveTimer) is running, or for a pre-defined time duration (e.g., 160 milliseconds) until the response is received.

[0186] As another example, the pre-defined point in non-blocking wait may mean that UE 100 proceeds with executing the conditional cell switch procedure until the UE 100 is ready to transmit the RRCReconfigurationComplete message as a cell switch finalization command for finalizing the cell switch procedure (in case of RACH-less cell switch). This RRCReconfigurationComplete message triggers higher layer procedures for cell switch finalization. In some cases, the finalization command may alternatively be a MAC CE message.

[0187] If the UE 100 does not receive any response from the access node 104 indicating the identifier of the second cell 122 (target cell) within a certain time period, the UE 100 may consider the conditional cell switch to be denied, and thus refrain from performing or completing the cell switch.

[0188] In another alternative, the UE 100 does not expect any response from the network (see FIG. 3A), apart from the usual retransmissions verifying that the message was successfully transmitted, such as hybrid automatic repeat request (HARQ) feedback. In this alternative, the leave indication may be transmitted at a pre-defined point in time, for example upon the one or more conditions being fulfilled, or at the end of the Tmeasure time period, and the UE 100 performs the conditional cell switch procedure without waiting for the response.

[0189] At 218, the access node 104 of the first cell 121 may transmit, to the UE 100, a response to the leave indication, wherein the response indicates a permission for performing the conditional cell switch procedure. In other words, the network indicates to the UE 100 to proceed to the target cell (e.g., the second cell 122). The response may comprise the same identifier (e.g., candidateld) of the target cell (e.g., the second cell 122) as the identifier comprised in the leave indication transmitted by the UE 100. The UE 100 may receive the response from the access node 104.

[0190] The response to the leave indication may be transmitted to the UE 100 based on or in response to receiving the response message (of 216) from the target access node 104B. In other words, the first cell (i.e., source cell) 121 may wait for the response message from the target cell 122.

[0191] Alternatively, the response to the leave indication may be transmitted to the UE 100 at 218 without receiving the response message from the target access node 104B at 216. For example, the access node 104 of the first cell 121 may transmit the response to the UE 100 after a pre-defined time period has passed (e.g., 5 to 40 milliseconds) after receiving the leave indication. In this way, inter-node signalling may be reduced.

[0192] The response of 218 may comprise at least one of: a cell switch command (e.g., LTM cell switch command) for performing the conditional cell switch procedure to the second cell 122 or to another target cell 123,124 that may be indicated in the measurement report (i.e., redirection of the cell switch), a TCI state activation command associated with the second cell 122 or another target cell 123,124 that may be indicated in the measurement report (i.e., redirection of the cell switch), a PDCCH order requesting the UE 100 to start a random-access procedure with the second cell 122 or another target cell 123,124 that may be indicated in the measurement report (i.e., redirection of the cell switch), a downlink control information (DCI) message (e.g., the DCI may comprise a field that indicates the acknowledgement of proceeding with the cell switch), a handover command (e.g., in an RRC message), or a MAC CE message defined for this purpose.

[0193] At 219, the UE 100 performs the conditional cell switch procedure from the first cell 121 to the second cell 122 (or to the another target cell 123, 124 if indicated in the response). The UE 100 may perform a RACH-based cell switch or a RACH-less cell switch to the second cell 122.

[0194] The UE 100 may perform the conditional cell switch procedure based on receiving the response from the access node 104 of the first cell 121 (in a blocking wait manner or a non-blocking wait manner as explained above). Alternatively, the UE 100 may perform the conditional cell switch procedure without waiting for the response.

[0195] At 220, the UE 100 completes the conditional cell switch procedure by transmitting a message (e.g., an RRCReconfigurationComplete message) to the target access node 104B to indicate that the cell switch procedure has been completed. The UE 100 may consider that the cell switch procedure is successfully completed, when the random-access procedure with the target cell 122 is successfully completed. Alternatively, for a RACH-less cell switch procedure (e.g., RACH-less LTM), the UE 100 may consider that the cell switch procedure is successfully completed, when the UE 100 determines that the target access node 104B has successfully received the first UL data from the UE 100.

[0196] FIG. 3A illustrates an example, where the UE 100 transmits the leave indication and performs (and completes) the conditional cell switch procedure to enter the second cell 122 (target cell) without waiting for a response from the network.

[0197] At 311, the UE 100 receives the configuration information from the access node 104 of the first cell 121 (corresponding to 206 of FIG. 2).

[0198] At 312, the signal level of the associated conditional event changes and the UE 100 determines that the one or more conditions are fulfilled (corresponding to 209 of FIG. 2).

[0199] At 313, the UE 100 transmits the leave indication based on determining that the one or more conditions are fulfilled (corresponding to 210 of FIG. 2). The UE 100 may transmit the leave indication at a pre-defined point in time, for example upon the one or more conditions being fulfilled.

[0200] At 314, the UE 100 may perform measurements during the Tmeasure time period to fullfill the accuracy requirement to evaluate the signal from the second cell 122 in such a way that it can be reported (if a measurement report would be sent).

[0201] At 315, the UE 100 transmits a RACH preamble to the (target) access node 104B of the second cell 122 in order to enter the second cell 122.

[0202] FIG. 3B illustrates an example, where the UE 100 waits for a response from the network in a blocking wait manner. In blocking wait, the UE 100 stops the execution flow of the conditional cell switch and waits until the network provides a permission to continue the conditional cell switch procedure for entering the second cell 122 (target cell).

[0203] At 321, the UE 100 receives the configuration information from the access node 104 of the first cell 121 (corresponding to 206 of FIG. 2).

[0204] At 322, the UE 100 determines that the one or more conditions are fulfilled (corresponding to 209 of FIG. 2).

[0205] At 323, the UE 100 transmits the leave indication based on determining that the one or more conditions are fulfilled (corresponding to 210 of FIG. 2).

[0206] At 324, the UE 100 waits for a response to the leave indication (corresponding to 217 of FIG. 2).

[0207] At 325, the UE 100 receives the response to the leave indication from the access node 104 of the first cell 121 (corresponding to 218 of FIG. 2)

[0208] At 326, after receiving the response, the UE 100 initiates the conditional cell switch procedure by performing measurements during the Tmeasure time period to fullfill the accuracy requirement to evaluate the signal from the second cell 122 in such a way that it can be reported (if a measurement report would be sent).

[0209] At 327, the UE 100 transmits a RACH preamble to the (target) access node 104B of the second cell 122 in order to enter the second cell 122 (and thus complete the cell switch).

[0210] FIG. 3C illustrates an example, where the UE 100 waits for a response from the network in a non-blocking wait manner. In non-blocking wait, the UE 100 proceeds with the execution flow of the conditional cell switch procedure but waits at a pre-defined point before proceeding with the final execution. The pre-defined point in non-blocking wait can be, for example, to wait until the UE 100 is ready to transmit the RACH preamble to the second cell 122 (target cell).

[0211] At 331, the UE 100 receives the configuration information from the access node 104 of the first cell 121 (corresponding to 206 of FIG. 2).

[0212] At 332, the UE 100 determines that the one or more conditions are fulfilled (corresponding to 209 of FIG. 2).

[0213] At 333, the UE 100 transmits the leave indication based on determining that the one or more conditions are fulfilled (corresponding to 210 of FIG. 2).

[0214] At 334, based on transmitting the leave indication, the UE 100 initiates the conditional cell switch procedure by performing measurements during the Tmeasure time period to fullfill the accuracy requirement to evaluate the signal from the second cell 122 in such a way that it can be reported (if a measurement report would be sent).

[0215] At 335, the UE 100 stops the conditional cell switch procedure and waits for a response to the leave indication (corresponding to 217 of FIG. 2).

[0216] At 336, the UE 100 receives the response to the leave indication from the access node 104 of the first cell 121 (corresponding to 218 of FIG. 2)

[0217] At 337, based on receiving the response, the UE 100 continues the conditional cell switch procedure by transmitting a RACH preamble to the (target) access node 104B of the second cell 122 in order to enter the second cell 122 (and thus complete the cell switch).

[0218] FIG. 4 illustrates an example of the timer (leaveTimer) described above.

[0219] At 401, the UE 100 determines that the one or more conditions are fulfilled (corresponding to 209 of FIG. 2).

[0220] At 402, the UE 100 may transmit the leave indication based on or in response determining that the one or more conditions are fulfilled (corresponding to 210 of FIG. 2). In this case, the timer (leaveTimer) 421 may be started upon transmitting the leave indication at 402 before the Tmeasure time period 403.

[0221] Alternatively, the UE 100 may transmit the leave indication at 404 after the Tmeasure time period 403, i.e., after meeting the measurement accuracy requirements associated with the target cell 122. In this case, the timer (leaveTimer) 422 may be started upon transmitting the leave indication at 404 after the Tmeasure time period 403.

[0222] In other words, the leave indication may be transmitted either before or after the UE 100 has measured the signal level of the target cell 122 properly (i.e., before or after the Tmeasure time period 403).

[0223] At 408, the UE 100 waits until the timer (leaveTimer) expires or until the response to the leave indication is received from the access node 104 of the first cell 121 before transmitting the RACH preamble to the target cell 122. The UE 100 may skip one or more RACH transmission occasions while waiting.

[0224] The timer (leaveTimer) 421, 422 may comprise one or more components of the interruption time ^TinterruptJ / such as Texecutton 405, Tue_.preparation 406, and / or Ta 407.

[0225] Texecution 405 refers to a time when the UE 100 starts to execute the conditional cell switch.

[0226] Tue..preparation 406 is a time for UE processing to prepare for the conditional cell switch.

[0227] Ta (T_delta) 407 is a time for fine time tracking and acquiring full timing information of the target cell 122.

[0228] Tiu / First-uL 409 is a time period of the interruption uncertainty (1U) in acquiring the first available RACH occasion in the target cell 122. It also includes the transmission of the first uplink data (First-UL) in the target cell 122 after completing the conditional cell switch.

[0229] FIG. 5 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1300 depicted in FIG. 13. For example, the apparatus 1300 may be, or comprise, or be comprised in, a user device (i.e., UE) 100, 102.

[0230] Referring to FIG. 5, in block 501, the apparatus 1300 receives, from an access node 104 of a first cell 121, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells 122,123,124 for the conditional cell switch procedure.

[0231] In block 502, the apparatus 1300 determines whether the one or more conditions are fulfilled.

[0232] In block 503, based on determining that the one or more conditions are fulfilled, the apparatus 1300 transmits, to the access node 104 of the first cell 121, a leave indication indicating that the apparatus 1300 intends to perform the conditional cell switch procedure from the first cell 121 (source cell) to a second cell 122 (target cell) comprised in the one or more candidate cells 122, 123, 124. The leave indication is transmitted before performing the conditional cell switch procedure.

[0233] Herein the conditional cell switch procedure may refer to, for example, an intra-DU cell switch (where both the source cell 121 and the target cell 122 are controlled by the same gNB or DU) or an inter-CU cell switch (where the source cell 121 and the target cell 122 are managed by different gNBs or CUs).

[0234] The leave indication may comprise at least one of: an identifier of at least the second cell 122 for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell 122, information of one or more beams from the second cell 122 for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell 122.

[0235] For example, the leave indication may be comprised in a medium access control control element message or a radio resource control message.

[0236] As another example, the leave indication may be comprised in a measurement report. The apparatus 1300 may perform one or more radio measurements associated with the one or more conditions on at least the second cell 122, wherein the leave indication is comprised in the measurement report for reporting the one or more radio measurements, and / or wherein the leave indication is transmitted based on obtaining a pre-defined number of measurements samples.

[0237] The apparatus 1300 may perform or initiate the conditional cell switch procedure based on transmitting the leave indication, wherein the leave indication may be transmitted at a pre-defined point in time.

[0238] FIG. 6 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1300 depicted in FIG. 13. For example, the apparatus 1300 may be, or comprise, or be comprised in, a user device (i.e., UE) 100,102.

[0239] Referring to FIG. 6, in block 601, the apparatus 1300 receives, from an access node 104 of a first cell 121, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells 122,123,124 for the conditional cell switch procedure.

[0240] In block 602, the apparatus 1300 determines whether the one or more conditions are fulfilled.

[0241] In block 603, based on determining that the one or more conditions are fulfilled, the apparatus 1300 transmits, to the access node 104 of the first cell 121, a leave indication indicating that the apparatus 1300 intends to perform the conditional cell switch procedure from the first cell 121 to a second cell 122 comprised in the one or more candidate cells 122, 123, 124. The leave indication is transmitted before performing the conditional cell switch procedure. For example, the leave indication may be transmitted in a measurement report.

[0242] The leave indication may comprise at least one of: an identifier of at least the second cell 122 for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell 122, information of one or more beams from the second cell 122 for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell 122.

[0243] In block 604, the apparatus 1300 starts a timer (e.g., leaveTimer) 421, 422 that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the timer 421, 422 is started based on transmitting the leave indication.

[0244] In block 605, the apparatus 1300 detects that the timer 421, 422 has expired.

[0245] In block 606, based on detecting that the timer 421,422 has expired, the apparatus 1300 determines whether one or more radio conditions on the first cell 121 and the second cell 122 are above a threshold.

[0246] The one or more radio conditions may comprise, for example, at least one of: reference signal received power, reference signal received quality, and / or signal-to-interference-plus-noise ratio.

[0247] In block 607, based on determining that the one or more radio conditions on the first cell 121 and the second cell 122 are above the threshold (block 606: yes), the apparatus 1300 transmits another measurement report to the access node 104 of the first cell 121.

[0248] FIG. 7 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1300 depicted in FIG. 13. For example, the apparatus 1300 may be, or comprise, or be comprised in, a user device (i.e., UE) 100,102.

[0249] Referring to FIG. 7, in block 701, the apparatus 1300 receives, from an access node 104 of a first cell 121, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells 122,123,124 for the conditional cell switch procedure.

[0250] In block 702, the apparatus 1300 determines whether the one or more conditions are fulfilled.

[0251] In block 703, based on determining that the one or more conditions are fulfilled, the apparatus 1300 transmits, to the access node 104 of the first cell 121, a leave indication indicating that the apparatus 1300 intends to perform the conditional cell switch procedure from the first cell 121 to a second cell 122 comprised in the one or more candidate cells 122, 123, 124. The leave indication is transmitted before performing the conditional cell switch procedure.

[0252] The leave indication may comprise at least one of: an identifier of at least the second cell 122 for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell 122, information of one or more beams from the second cell 122 for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell 122.

[0253] In block 704, the apparatus 1300 starts a timer (e.g., leaveTimer) 421, 422 that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the timer 421, 422 is started based on transmitting the leave indication.

[0254] In block 705, the apparatus 1300 detects that the timer 421, 422 has expired.

[0255] In block 706, based on detecting that the timer 421, 422 has expired, the apparatus 1300 determines whether one or more radio conditions on the first cell 121 are above a threshold.

[0256] The one or more radio conditions may comprise, for example, at least one of: reference signal received power, reference signal received quality, and / or signal-to-interference-plus-noise ratio.

[0257] In block 707, based on determining that the one or more radio conditions on the first cell 121 are above the threshold (block 706: yes), the apparatus 1300 refrains from performing (or initiating) the conditional cell switch procedure from the first cell 121 to the second cell 122.

[0258] Alternatively, in block 708, based on determining that the one or more radio conditions on the first cell 121 are not above the threshold (block 706: no, e.g., the one or more radio conditions on the first cell 121 are below the threshold), the apparatus 1300 performs the conditional cell switch procedure.

[0259] FIG. 8 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1300 depicted in FIG. 13. For example, the apparatus 1300 may be, or comprise, or be comprised in, a user device (i.e., UE) 100,102.

[0260] Referring to FIG. 8, in block 801, the apparatus 1300 receives, from an access node 104 of a first cell 121, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells 122,123,124 for the conditional cell switch procedure.

[0261] In block 802, the apparatus 1300 determines whether the one or more conditions are fulfilled.

[0262] In block 803, based on determining that the one or more conditions are fulfilled, the apparatus 1300 transmits, to the access node 104 of the first cell 121, a leave indication indicating that the apparatus 1300 intends to perform the conditional cell switch procedure from the first cell 121 to a second cell 122 comprised in the one or more candidate cells 122, 123, 124. The leave indication is transmitted before performing the conditional cell switch procedure.

[0263] The leave indication may comprise at least one of: an identifier of at least the second cell 122 for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell 122, information of one or more beams from the second cell 122 for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell 122.

[0264] In block 804, the apparatus 1300 determines whether a response to the leave indication has been received from the access node 104 of the first cell 121 within a pre-defined time period (e.g., before the timer 421, 422 expires) to indicate a permission for performing the conditional cell switch procedure from the first cell 121 to the second cell 122.

[0265] The response may comprise at least one of: a cell switch command for performing the conditional cell switch procedure, a transmission configuration indicator state activation command associated with the second cell, a physical downlink control channel order requesting the user device to start a random-access procedure with the second cell, a downlink control information message, a handover command in a radio resource control message, or a medium access control control element message.

[0266] In block 805, based on determining that the response has not been received within the pre-defined time period (block 804: no), the apparatus 1300 refrains from performing or initiating the conditional cell switch procedure.

[0267] Alternatively, in block 806, based on determining that the response has been received within the pre-defined time period (block 804: yes), the apparatus 1300 performs or initiates the conditional cell switch procedure.

[0268] FIG. 9 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1300 depicted in FIG. 13. For example, the apparatus 1300 may be, or comprise, or be comprised in, a user device (i.e., UE) 100,102.

[0269] Referring to FIG. 9, in block 901, the apparatus 1300 receives, from an access node 104 of a first cell 121, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells 122,123,124 for the conditional cell switch procedure.

[0270] In block 902, the apparatus 1300 determines whether the one or more conditions are fulfilled.

[0271] In block 903, based on determining that the one or more conditions are fulfilled, the apparatus 1300 transmits, to the access node 104 of the first cell 121, a leave indication indicating that the apparatus 1300 intends to perform the conditional cell switch procedure from the first cell 121 to a second cell 122 comprised in the one or more candidate cells 122, 123, 124. The leave indication is transmitted before performing the conditional cell switch procedure.

[0272] The leave indication may comprise at least one of: an identifier of at least the second cell 122 for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell 122, information of one or more beams from the second cell 122 for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell 122.

[0273] In block 904, the apparatus 1300 initiates the conditional cell switch procedure based on transmitting the leave indication.

[0274] In block 905, the apparatus 1300 stops the conditional cell switch procedure at a pre-defined point.

[0275] In block 906, the apparatus 1300 determines whether a response to the leave indication has been received from the access node 104 of the first cell 121 within a pre-defined time period (e.g., before the timer 421, 422 expires) to indicate a permission for performing the conditional cell switch procedure from the first cell 121 to the second cell 122.

[0276] The response may comprise at least one of: a cell switch command for performing the conditional cell switch procedure, a transmission configuration indicator state activation command associated with the second cell, a physical downlink control channel order requesting the user device to start a random-access procedure with the second cell, a downlink control information message, a handover command in a radio resource control message, or a medium access control control element message.

[0277] In block 907, based on determining that the response has not been received within the pre-defined time period (block 906: no), the apparatus 1300 refrains from continuing or completing the conditional cell switch procedure.

[0278] Alternatively, in block 908, based on determining that the response has been received within the pre-defined time period (block 906: yes), the apparatus 1300 continues the conditional cell switch procedure from the pre-defined point.

[0279] FIG. 10 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1400 depicted in FIG. 14. For example, the apparatus 1400 may be, or comprise, or be comprised in, an access node 104 of a first cell 121.

[0280] Referring to FIG. 10, in block 1001, the apparatus 1400 (e.g., access node 104 of the first cell 121) transmits, to a user device 100, 102, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells 122,123,124 for the conditional cell switch procedure.

[0281] In block 1002, the apparatus 1400 receives, from the user device 100, 102, a leave indication indicating that the user device 100, 102 intends to perform a conditional cell switch procedure from the first cell 121 to a second cell 122 comprised in the one or more candidate cells 122,123,124.

[0282] The leave indication may comprise at least one of: an identifier of at least the second cell 122 for which the one or more conditions were fulfilled, information on the one or more conditions determined to be fulfilled at least for the second cell 122, information of one or more beams from the second cell 122 for which the one or more conditions were fulfilled, or a status of timing advance acquisition with the second cell 122.

[0283] For example, the leave indication may be comprised in a medium access control control element message or a radio resource control message or a measurement report.

[0284] In block 1003, based on receiving the leave indication, the apparatus 1400 generates a message for an access node 104B of the second cell 122, the message indicating that the user device 100, 102 intends to perform the conditional cell switch procedure. The access node 104B of the second cell 122 (target cell) may also be referred to as a target access node.

[0285] In block 1004, the apparatus 1400 transmits the message to the access node 104B of the second cell 122.

[0286] The message transmitted to the access node 104B of the second cell 122 may comprise context information associated with the user device 100,102.

[0287] Alternatively, or additionally, the message transmitted to the access node 104B of the second cell 122 may comprise the information of the one or more beams from the second cell for which the one or more conditions were fulfilled.

[0288] The apparatus 1400 may transmit, to the user device 100, 102, a response to the leave indication, wherein the response indicates a permission for performing the conditional cell switch procedure from the first cell 121 to the second cell 122.

[0289] The response may comprise at least one of: a cell switch command for performing the conditional cell switch procedure, a transmission configuration indicator state activation command associated with the second cell 122, a physical downlink control channel order requesting the user device 100, 102 to start a random-access procedure with the second cell 122, a downlink control information message, a handover command in a radio resource control message, or a medium access control control element message.

[0290] The apparatus 1400 may receive, from the access node 104B of the second cell 122, a response message indicating an acknowledgement for receiving the message, wherein the response to the leave indication may be transmitted to the user device 100,102 based on receiving the response message from the access node 104B of the second cell 122.

[0291] FIG. 11 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1400 depicted in FIG. 14. For example, the apparatus 1400 may be, or comprise, or be comprised in, an access node 104B of a second cell 122. The access node 104B of the second cell 122 (target cell) may also be referred to as a target access node.

[0292] Referring to FIG. 11, in block 1101, the apparatus 1400 (e.g., access node 104B of the second cell 122) receives, from an access node 104 of a first cell 121, a message indicating that a user device 100, 102 intends to perform a conditional cell switch procedure from the first cell 121 to the second cell 122.

[0293] In block 1102, the apparatus 1400 prepares the second cell 122 for the conditional cell switch procedure based on the message.

[0294] The message may comprise information of one or more beams from the second cell 122 for which one or more conditions related to the conditional cell switch procedure were fulfilled. The apparatus 1400 may activate uplink resources for the user device 100,102 on the one or more beams from the second cell 122 based on the message.

[0295] Alternatively, or additionally, the message may comprise context information associated with the user device 100,102, wherein the second cell 122 may be prepared based on the context information.

[0296] FIG. 12 illustrates a flow chart according to an example embodiment of a method for controlling cell switch execution. The method may be performed by an apparatus 1400 depicted in FIG. 14. For example, the apparatus 1400 may be, or comprise, or be comprised in, an access node 104B of a second cell 122. The access node 104B of the second cell 122 (target cell) may also be referred to as a target access node.

[0297] Referring to FIG. 12, in block 1201, the apparatus 1400 (e.g., access node 104B of the second cell 122) receives, from an access node 104 of a first cell 121, a message indicating that a user device 100, 102 intends to perform a conditional cell switch procedure from the first cell 121 to the second cell 122.

[0298] In block 1202, the apparatus 1400 starts a timer based on receiving the message, wherein the timer is set to expire after a pre-defined time period.

[0299] In block 1203, the apparatus 1400 prepares the second cell 122 for the conditional cell switch procedure based on the message.

[0300] The message comprises context information associated with the user device 100, 102, wherein the second cell 122 may be prepared based on the context information.

[0301] The message may further comprise information of one or more beams from the second cell 122 for which one or more conditions related to the conditional cell switch procedure were fulfilled. The apparatus 1400 may activate uplink resources for the user device 100,102 on the one or more beams from the second cell 122 based on the message.

[0302] In block 1204, the apparatus 1400 detects that the timer has expired.

[0303] In block 1205, the apparatus 1400 releases or deletes a configuration associated with the context information based on detecting that the timer has expired.

[0304] The blocks, related functions, and information exchanges (messages) described above by means of FIG. 2 and FIGS. 5 to 12 are in no absolute chronological order, and some of them may be performed simultaneously or in an order differing from the described one. Other functions can also be executed between them or within them, and other information may be sent, and / or other rules applied. Some of the blocks or part of the blocks or one or more pieces of information can also be left out or replaced by a corresponding block or part of the block or one or more pieces of information.

[0305] 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.

[0306] FIG. 13 illustrates an example of an apparatus 1300 comprising means for performing one or more of the example embodiments (e.g., the functions of the UE 100 of FIG. 2, or any of the methods of FIGS. 5 to 9) described above. For example, the apparatus 1300 may be an apparatus such as, or comprising, or comprised in, a user device 100,102.

[0307] The apparatus 1300 may comprise a circuitry or a chipset applicable for realizing one or more of the example embodiments described above. For example, the apparatus 1300 may comprise at least one processor 1310. The at least one processor 1310 interprets instructions (e.g., computer program instructions) and processes data. The at least one processor 1310 may comprise one or more programmable processors. The at least one processor 1310 may comprise programmable hardware with embedded firmware and may, alternatively or additionally, comprise one or more application-specific integrated circuits (ASICs).

[0308] The at least one processor 1310 is coupled to at least one memory 1320. The at least one processor is configured to read and write data to and from the at least one memory 1320. The at least one memory 1320 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 randomaccess 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 1320 stores computer readable instructions that are executed by the at least one processor 1310 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 1310 executes the instructions using volatile memory for temporary storage of data and / or instructions. The computer readable instructions may refer to computer program code.

[0309] The computer readable instructions may have been pre-stored to the at least one memory 1320 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 1310 causes the apparatus 1300 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.

[0310] In the context of this document, a "memory" or “computer-readable media” or "computer-readable medium” may be any non-transitoiy 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).

[0311] The apparatus 1300 may further comprise, or be connected to, an input unit 1330. The input unit 1330 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 1330 may comprise an interface to which external devices may connect to.

[0312] The apparatus 1300 may also comprise an output unit 1340. 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 1340 may further comprise one or more audio outputs. The one or more audio outputs may be for example loudspeakers.

[0313] The apparatus 1300 further comprises a connectivity unit 1350. The connectivity unit 1350 enables wireless connectivity to one or more external devices. The connectivity unit 1350 comprises at least one transmitter and at least one receiver that may be integrated to the apparatus 1300 or that the apparatus 1300 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 1350 may comprise an integrated circuit or a set of integrated circuits that provide the wireless communication capability for the apparatus 1300. Alternatively, the wireless connectivity may be a hardwired application-specific integrated circuit (ASIC). The connectivity unit 1350 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 1350 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.

[0314] It is to be noted that the apparatus 1300 may further comprise various components not illustrated in FIG. 13. The various components may be hardware components and / or software components.

[0315] FIG. 14 illustrates an example of an apparatus 1400 comprising means for performing one or more of the example embodiments (e.g., the functions of the access node 104 or 104B of FIG. 2, or any of the methods of FIGS. 10 to 12) described above. For example, the apparatus 1400 may be an apparatus such as, or comprising, or comprised in, an access node 104 (e.g., a gNB or a DU) of a first cell 121, or an access node 104B (e.g., a gNB or a DU) of a second cell 122.

[0316] The apparatus 1400 may comprise, for example, a circuitry or a chipset applicable for realizing one or more of the example embodiments described above. The apparatus 1400 may be an electronic device comprising one or more electronic circuitries. The apparatus 1400 may comprise a communication control circuitry 1410 such as at least one processor, and at least one memory 1420 storing instructions 1422 which, when executed by the at least one processor, cause the apparatus 1400 to carry out one or more of the example embodiments described above. Such instructions 1422 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.

[0317] The processor is coupled to the memory 1420. The processor is configured to read and write data to and from the memory 1420. The memory 1420 may comprise one or more memory units. The memory units may be volatile or non-volatile. It is to be noted that there maybe one or more units of non-volatile memory and one or more units of volatile memoiy or, alternatively, one or more units of non-volatile memory, or, alternatively, one or more units of volatile memory. Volatile memory may be for example random-access memory (RAM), dynamic random-access memory (DRAM) or synchronous dynamic random-access memory (SDRAM). Non-volatile memory may be for example read-only memory (ROM), programmable read-only memory (PROM), electronically erasable programmable read-only memory (EEPROM), flash memory, optical storage or magnetic storage. In general, memories may be referred to as non-transitory computer readable media. The term "non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM). The memory 1420 stores computer readable instructions that are executed by the processor. For example, nonvolatile memory stores the computer readable instructions, and the processor executes the instructions using volatile memoiy for temporary storage of data and / or instructions.

[0318] The computer readable instructions may have been pre-stored to the memory 1420 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 1400 to perform one or more of the functionalities described above.

[0319] The memoiy 1420 may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memoiy 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.

[0320] The apparatus 1400 may further comprise or be connected to a communication interface 1430, 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 1430 comprises at least one transmitter (Tx) and at least one receiver (Rx) that may be integrated to the apparatus 1400 or that the apparatus 1400 may be connected to. The communication interface 1430 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 1430 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.

[0321] The communication interface 1430 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 1400 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 other access nodes of the wireless communication network.

[0322] The apparatus 1400 may further comprise a scheduler 1440 that is configured to allocate radio resources. The scheduler 1440 may be configured along with the communication control circuitry 1410 or it may be separately configured.

[0323] It is to be noted that the apparatus 1400 may further comprise various components not illustrated in FIG. 14. The various components may be hardware components and / or software components.

[0324] As used in this application, the term “circuitry" may refer to one or more or all of the following: a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry); and b) combinations of hardware circuits and software, such as (as applicable): i) a combination of analog and / or digital hardware circuit(s) with software / firmware and ii) any portions of hardware processor(s) with software (including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone, to perform various functions); and c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (for example firmware) for operation, but the software may not be present when it is not needed for operation.

[0325] 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.

[0326] 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 maybe rearranged and / or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

[0327] 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

1. A user device comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the user device at least to:receive, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure;determine whether the one or more conditions are fulfilled; andbased on determining that the one or more conditions are fulfilled, transmit, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells,wherein the leave indication is transmitted before performing the conditional cell switch procedure.

2. The user device of claim 1, wherein the leave indication comprises at least one of:an identifier of at least the second cell for which the one or more conditions were fulfilled,information on the one or more conditions determined to be fulfilled at least for the second cell,information of one or more beams from the second cell for which the one or more conditions were fulfilled, ora status of timing advance acquisition with the second cell.

3. The user device of any preceding claim, wherein the leave indication is comprised in a medium access control control element message or a radio resource control message.

4. The user device of any of claims 1 to 2, further being caused to:perform one or more radio measurements associated with the one or more conditions on at least the second cell,wherein the leave indication is comprised in a measurement report for reporting the one or more radio measurements, and / orwherein the leave indication is transmitted based on obtaining a pre-defined number of measurements samples.

5. The user device of claim 4, further being caused to:start a timer that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the timer is started based on transmitting the leave indication;based on detecting that the timer has expired, determine whether one or more radio conditions on the first cell and the second cell are above a threshold; andbased on determining that the one or more radio conditions on the first cell and the second cell are above the threshold, transmit another measurement report to the access node of the first cell.

6. The user device of any of claims 1 to 4, further being caused to:start a timer that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the timer is started based on transmitting the leave indication;based on detecting that the timer has expired, determine whether one or more radio conditions on the first cell are above a threshold; andbased on determining that the one or more radio conditions on the first cell are above the threshold, refrain from performing the conditional cell switch procedure from the first cell to the second cell.

7. The user device of any of claims 1 to 4, further being caused to:start a timer that is set to expire after a pre-defined time duration indicated in the configuration information, wherein the timer is started based on transmitting the leave indication;based on detecting that the timer has expired, determine whether one or more radio conditions on the first cell are below a threshold; andbased on determining that the one or more radio conditions on the first cell are below the threshold, perform the conditional cell switch procedure.

8. The user device of any of claims 1 to 5, further being caused to:perform the conditional cell switch procedure based on transmitting the leave indication,wherein the leave indication is transmitted at a pre-defined point in time.

9. The user device of any of claims 1 to 5, further being caused to:determine whether a response to the leave indication has been received from the access node of the first cell within a pre-defined time period; andbased on determining that the response has not been received within the predefined time period, refrain from performing the conditional cell switch procedure.

10. The user device of any of claims 1 to 5, further being caused to:receive, from the access node of the first cell, a response to the leave indication, wherein the response indicates a permission for performing the conditional cell switch procedure; andperform the conditional cell switch procedure based on receiving the response from the access node of the first cell.

11. The user device of claim 10, further being caused to:initiate the conditional cell switch procedure based on transmitting the leave indication;stop the conditional cell switch procedure at a pre-defined point; andcontinue the conditional cell switch procedure from the pre-defined point based on receiving the response to the leave indication from the access node of the first cell.

12. The user device of any of claims 9 to 11, wherein the response comprises at least one of:a cell switch command for performing the conditional cell switch procedure,a transmission configuration indicator state activation command associated with the second cell,a physical downlink control channel order requesting the user device to start a random-access procedure with the second cell,a downlink control information message,a handover command in a radio resource control message, ora medium access control control element message.

13. An access node of a first cell, the access node comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to:transmit, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure;receive, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells;based on receiving the leave indication, generate a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; andtransmit the message to the access node of the second cell.

14. The access node of claim 13, wherein the message comprises context information associated with the user device.

15. The access node of any of claims 13 to 14, wherein the leave indication received from the user device comprises information of one or more beams from the second cell for which the one or more conditions were fulfilled,wherein the message transmitted to the access node of the second cell comprises the information of the one or more beams from the second cell for which the one or more conditions were fulfilled.

16. The access node of any of claims 13 to 15, further being caused to:transmit, to the user device, a response to the leave indication, wherein the response indicates a permission for performing the conditional cell switch procedure from the first cell to the second cell.

17. The access node of claim 16, further being caused to:receive, from the access node of the second cell, a response message indicating an acknowledgement for receiving the message,wherein the response to the leave indication is transmitted to the user device based on receiving the response message from the access node of the second cell.

18. An access node of a second cell, the access node comprising at least one processor, and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to:receive, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; andprepare the second cell for the conditional cell switch procedure based on the message.

19. The access node of claim 18, further being caused to:activate uplink resources for the user device on one or more beams from the second cell based on the message,wherein the message comprises information of the one or more beams from the second cell for which one or more conditions related to the conditional cell switch procedure were fulfilled.

20. The access node of any of claims 18 to 19, wherein the message comprises context information associated with the user device,wherein the second cell is prepared based on the context information.

21. The access node of claim 20, further being caused to:start a timer based on receiving the message, wherein the timer is set to expire after a pre-defined time period; andrelease a configuration associated with the context information based on detecting that the timer has expired.

22. A method comprising:receiving, by a user device, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure;determining, by the user device, whether the one or more conditions are fulfilled; andbased on determining that the one or more conditions are fulfilled, transmitting, by the user device, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells,wherein the leave indication is transmitted before performing the conditional cell switch procedure.

23. A method comprising:transmitting, by an access node of a first cell, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure;receiving, by the access node of the first cell, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells;based on receiving the leave indication, generating, by the access node of the first cell, a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; andtransmitting, by the access node of the first cell, the message to the access node of the second cell.

24. A method comprising:receiving, by an access node of a second cell, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; andpreparing, by the access node of the second cell, the second cell for the conditional cell switch procedure based on the message.

25. A non-transitory computer readable medium comprising program instructions which, when executed by a user device, cause the user device to perform at least the following:receiving, from an access node of a first cell, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure;determining whether the one or more conditions are fulfilled; andbased on determining that the one or more conditions are fulfilled, transmitting, to the access node of the first cell, a leave indication indicating that the user device intends to perform the conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells,wherein the leave indication is transmitted before performing the conditional cell switch procedure.

26. A non-transitoiy computer readable medium comprising program instructions which, when executed by an access node of a first cell, cause the access node to perform at least the following:transmitting, to a user device, configuration information related to a conditional cell switch procedure, the configuration information indicating one or more conditions and one or more candidate cells for the conditional cell switch procedure;receiving, from the user device, a leave indication indicating that the user device intends to perform a conditional cell switch procedure from the first cell to a second cell comprised in the one or more candidate cells;based on receiving the leave indication, generating a message for an access node of the second cell, the message indicating that the user device intends to perform the conditional cell switch procedure; andtransmitting the message to the access node of the second cell.

27. A non-transitory computer readable medium comprising program instructions which, when executed by an access node of a second cell, cause the access 5 node to perform at least the following:receiving, from an access node of a first cell, a message indicating that a user device intends to perform a conditional cell switch procedure from the first cell to the second cell; andpreparing the second cell for the conditional cell switch procedure based on 10 the message.

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