Enhancement of connected mode mobility

Abstract

Example embodiments of the present disclosure relate to enhancements for connected mode mobility. An apparatus receives, from a network device, an indication relating to a change in operating state of a serving cell, the indication triggering at least one conditional switching (CHO) event at the apparatus. The apparatus determines whether at least one CHO event configured for the at least one candidate cell satisfies a CHO condition associated with the CHO event. Based on determining that each of the CHO events configured for the at least one candidate cell does not satisfy the CHO condition, the apparatus selects a target cell based on a cell selection rule. In this manner, UE mobility and service continuity may be ensured regardless of changes in the network energy saving (NES) state of the serving cell. In addition, implementation of NES functionality may be improved.

Description

Technical Field

[0001] Various example embodiments of the present disclosure relate generally to the field of telecommunications, and in particular, to methods, devices, apparatus, and computer-readable storage media for connected mode mobility enhancement. Background Art

[0002] In 5G NR, energy-saving technologies have been developed on both the UE and network sides. In particular, energy savings achieved based on base station (BS) transmission and / or reception are referred to as network energy savings (NES). Various NES modes or states designed for different deployment scenarios, network conditions, and the like have been proposed. During the NES state of switching a serving cell, UE mobility from that cell may be triggered. In other words, it is possible to handover a UE residing on a serving cell to another cell.

[0003] Therefore, it is expected that the UE will move out of the cell immediately or faster in order to minimize service interruption for the UE and allow the network to implement energy saving functions as quickly as possible. Summary of the Invention

[0004] In general, example embodiments of the present disclosure provide solutions for connected mode mobility enhancement.

[0005] In a first aspect of the present disclosure, an apparatus is provided. The apparatus includes: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receive an indication related to a change in an operating state of a serving cell from a network device, indicating triggering of at least one conditional handover (CHO) event at the apparatus; determine whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; and select a target cell based on a cell selection rule based on a determination that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition.

[0006] In a second aspect of the present disclosure, an apparatus is provided. The apparatus includes: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: transmit a configuration of a cell selection rule to a terminal device in a serving cell provided by the apparatus, the cell selection rule being used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and transmit an indication related to a change in the operating state of the serving cell to the terminal device, indicating triggering of at least one CHO event at the terminal device.

[0007] In a third aspect of the present disclosure, a method is provided. The method includes: receiving, at a terminal device, an indication from a network device regarding a change in an operating state of a serving cell, indicating triggering of at least one conditional handover (CHO) event at the terminal device; determining whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; and selecting a target cell based on a cell selection rule based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition.

[0008] In a fourth aspect of the present disclosure, a method is provided. The method includes: transmitting, at a network device, a configuration of a cell selection rule to a terminal device in a serving cell provided by the network device, wherein the cell selection rule is used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and transmitting, to the terminal device, an indication related to a change in an operating state of the serving cell, indicating that at least one CHO event is triggered at the terminal device.

[0009] In a fifth aspect of the present disclosure, a first apparatus is provided. The first apparatus includes: a component for receiving an indication related to a change in an operating state of a serving cell from a second apparatus, indicating that at least one conditional handover (CHO) event is triggered at the first apparatus; a component for determining whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; and a component for selecting a target cell based on a cell selection rule based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition.

[0010] In a sixth aspect of the present disclosure, a second apparatus is provided. The second apparatus includes: a component for transmitting a configuration of a cell selection rule to a first apparatus in a serving cell provided by the second apparatus, wherein the cell selection rule is used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and a component for transmitting an indication related to a change in an operating state of the serving cell to the first apparatus, indicating that at least one CHO event is triggered at the first apparatus.

[0011] In a seventh aspect of the present disclosure, a computer-readable medium is provided. The computer-readable medium includes instructions stored thereon, the instructions being configured to cause an apparatus to: receive an indication related to a change in an operating state of a serving cell from a network device, indicating triggering of at least one conditional handover (CHO) event at the apparatus; determine whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; and select a target cell based on a cell selection rule based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition.

[0012] In an eighth aspect of the present disclosure, a computer-readable medium is provided. The computer-readable medium includes instructions stored thereon, the instructions being configured to cause an apparatus to: transmit a configuration of a cell selection rule to a terminal device in a serving cell provided by the apparatus, the cell selection rule being used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and transmit an indication related to a change in an operating state of the serving cell to the terminal device, indicating triggering of at least one CHO event at the terminal device.

[0013] In a ninth aspect of the present disclosure, a computer program is provided, comprising instructions which, when executed by an apparatus, cause the apparatus to at least perform the following: receive an indication from a network device relating to a change in the operating state of a serving cell, indicating that at least one conditional switching (CHO) event is triggered at the apparatus; determine whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; and select a target cell based on a cell selection rule based on determining that none of the CHO events configured for at least one candidate cell satisfies the CHO condition.

[0014] In a tenth aspect of the present disclosure, a computer program is provided, comprising instructions which, when executed by an apparatus, cause the apparatus to at least perform the following: transmit a configuration of a cell selection rule to a terminal device in a service cell provided by the apparatus, the cell selection rule being used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and transmit an indication related to a change in the operating state of the service cell to the terminal device, indicating that at least one CHO event is triggered at the terminal device.

[0015] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0017] Figure 1 An example communication environment is shown in which example embodiments of the present disclosure may be implemented;

[0018] Figure 2 shows a signaling diagram for connected mode mobility in an NES cell according to some example embodiments of the present disclosure;

[0019] Figure 3 A flowchart illustrating a method implemented at a terminal device according to some example embodiments of the present disclosure is shown;

[0020] Figure 4 A flowchart illustrating a method implemented at a network device according to some example embodiments of the present disclosure is shown;

[0021] Figure 5 shows a simplified block diagram of a device suitable for implementing an example embodiment of the present disclosure; and

[0022] Figure 6 A block diagram of an example computer-readable medium is shown, according to some example embodiments of the present disclosure.

[0023] Throughout the drawings, the same or similar reference numerals denote the same or similar elements. DETAILED DESCRIPTION

[0024] The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described only for illustrative purposes and to assist those skilled in the art in understanding and implementing the present disclosure, without implying any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways other than those described below.

[0025] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0026] References in this disclosure to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment will include that particular feature, structure, or characteristic. Moreover, these phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in conjunction with an example embodiment, it is intended that, whether or not explicitly described, one skilled in the art would recognize that such feature, structure, or characteristic may be applied in conjunction with other embodiments.

[0027] It should be understood that although the terms "first" and "second" etc. may be used to describe various elements in this document, these elements should not be limited to these terms. These terms are only used to distinguish the functions of the various elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0028] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the example embodiments. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the terms "comprises," "includes," "has," "has," "contains," and / or "comprising," when used herein, specify the presence of stated features, elements, and / or components, etc., but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0029] As used herein, “at least one of: ” and “at least one of ” and similar expressions, where a list of two or more elements is linked by “and” or “or”, mean at least any one of these elements, or any two or more of these elements, or at least all of the elements.

[0030] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware circuit implementation only (e.g., implementation in purely analog and / or digital circuits) and (b) a combination of hardware circuitry and software such as (if applicable): (i) a combination of analog and / or digital hardware circuits and software / firmware and (ii) any portion of a hardware processor with software (including digital signal processor(s), software, and memory(s) that work together to enable a device (such as a mobile phone or server) to perform various functions) and (c) Hardware circuit(s) and / or processor(s) that require software (e.g., firmware) for operation, such as microprocessor(s) or portion(s) of microprocessor(s), but where the software is not required for operation, the software may not be present.

[0031] This definition of circuitry applies to all uses of the term in this application. 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 portions of a hardware circuit or server and its (or their) accompanying software and / or firmware. For example, the term "circuitry" also covers, where applicable to a particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or networking device.

[0032] As used herein, the term "communication network" refers to a network that follows any suitable communication standard, such as a fifth generation (5G) system, long term evolution (LTE), advanced long term evolution (LTE-A), wideband code division multiple access (WCDMA), high speed packet access (HSPA), narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal equipment and the network equipment in the communication network can be performed according to any suitable generation communication protocol, including but not limited to first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) new radio (NR) communication protocol, and / or any other protocol currently known or under development. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communications, there will inevitably be future types of communication technologies and systems that can implement the present disclosure. The scope of the present disclosure should not be considered to be limited to the above-mentioned systems.

[0033] As used herein, the term "network device" refers to a node in a communication network through which a terminal device accesses the network and receives services. Depending on the terminology and technology used, a network device can refer to a base station (BS) or access point (AP), for example, a NodeB (NodeB or NB), an evolved NodeB (eNodeB or eNB), a next-generation NodeB (NR NB), a remote radio unit (RRU), a radio head (RH), a remote radio head (RRH), an integrated access and backhaul (IAB) node, a relay, a low-power node (such as a femto, pico, etc.). A network device may be defined as part of a gNB, such as in a CU / DU split, in which case the network device is defined as a gNB-CU or gNB-DU.

[0034] The term "terminal device" refers to any terminal device with wireless communication capabilities. As an example and not limitation, a terminal device may refer to a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cellular phones, smart phones, voice over IP (VoIP) phones, wireless local loop phones, tablet computers, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image acquisition terminal devices (such as digital cameras), game terminal devices, music storage and playback devices, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop mounted devices (LMEs), USB dongles, smart devices, wireless client equipment (CPEs), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronic devices, devices operating on commercial and / or industrial wireless networks, etc. The terminal device may also correspond to the mobile terminal (MT) part of an integrated access and backhaul (IAB) node (also known as a relay node). In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0035] As used herein, the term "control device" refers to any entity / function / device / apparatus used for control. In some example embodiments, the control device is a device used to implement domain coordination, network optimization, and network management functions.

[0036] While the functions described herein may be performed in fixed and / or wireless network nodes in various example embodiments, in other example embodiments, these functions may be implemented in a user equipment device (such as a mobile phone or tablet or desktop computer or mobile IoT device or fixed IoT device). For example, the user equipment device can be equipped with corresponding capabilities as described in conjunction with (multiple) fixed and / or wireless network nodes, as appropriate. The user equipment device may be a user device and / or a control device (such as a chipset or processor) that, when installed in the user device, is configured to control the user device. Examples of these functions include bootstrap server functions and / or home subscriber servers, which may be implemented in the user equipment device by providing software to the user equipment device that is configured to cause the user equipment device to perform from the perspective of these functions / nodes.

[0037] Conditional Handover (CHO) has been proposed to facilitate UE mobility when the NES state of the serving cell changes. CHO is defined as a handover (HO) performed by the UE when one or more handover execution conditions are met. Specifically, a CHO configuration may contain the configuration of at least one CHO candidate cell managed by at least one candidate gNB and (multiple) execution conditions generated by the source gNB. The UE may start evaluating at least one execution condition upon receiving the CHO configuration. Upon receiving a HO command (without CHO configuration) before any CHO execution conditions are met, the UE performs the HO procedure regardless of any previously received CHO configuration. Once the HO is performed, the UE may stop evaluating at least one execution condition.

[0038] In an example scenario, the UE is configured with at least one CHO event that will be triggered based on the NES state and / or some NES cell-specific CHO conditions. Specifically, a change in the NES state or NES mode of a cell can trigger CHO. However, when the NES state changes, the CHO conditions are not always met because the CHO candidates may not meet the quality requirements set in the CHO configuration. According to the existing CHO mechanism, if no candidate cell meets the CHO conditions, it will postpone the UE's departure from the cell until a radio link failure (RLF) is declared, which may take a very long time (e.g., several seconds, tens of seconds, etc.). In this case, service continuity will be affected, thereby reducing the implementation prospects of the NES function.

[0039] Therefore, for situations where CHO is triggered based on a specific NES state or NES state change, it is necessary to enhance the connected mode mobility. The enhanced mechanism aims to ensure that the UE can leave the serving cell. Sample Environment

[0040] Figure 1 An example communication environment 100 is shown in which example embodiments of the present disclosure may be implemented. Communication environment 100 may be a communication network supporting NES functionality. Communication network 100 includes a terminal device 110 and a network device 120. Hereinafter, terminal device 110 and network device 120 may also be referred to as UE 110 and gNB 120, respectively.

[0041] In the communication network 100, there are a plurality of cells 12 to 18 for providing radio coverage. Figure 1As shown, terminal device 110 is located in cell 12 and is served by network device 120. In other words, cell 12 is the serving cell for terminal device 110. Terminal device 110 may be in RRC_CONNECTED mode with mobility between cells 12 to 18. It should be understood that cells 14 to 18 may or may not be provided by network device 120. Accordingly, embodiments of the present disclosure are not limited in this respect.

[0042] Network device 120 may provide more than one cell, including serving cell 12. To conserve energy, network device 120 may control the operating state of the cell. For example, network device 120 may control cell 12 to switch between a normal state or a non-NES state and an NES state. It may also control cell 12 to switch between different NES states. Furthermore, network device 120 may control cell 12 to be shut down or prohibited from use by terminal device 110. If the operating state of serving cell 12 changes to a certain NES state, shut down state, or prohibited state, terminal device 110 may need to switch from serving cell 12 to another cell.

[0043] To facilitate the mobility of the terminal device 110, the network device 120 may configure at least one CHO event for the terminal device 110 that is triggered based on a change in the operating state of the serving cell 12. At least one CHO event may be configured for at least one candidate cell. For example, at least one CHO event may involve a group of candidate cells 14 to 18 that are prepared for potential handover. Furthermore, the CHO event may be associated with a CHO condition. If at least one of the candidate cells satisfies the CHO condition, the terminal device 110 may select a target cell from the at least one candidate cell. If none of the candidate cells satisfies the CHO condition, the terminal device 110 may select a target cell based on a cell selection rule, which will be discussed in detail below.

[0044] It should be understood that Figure 1 The number of devices and their connections shown is for illustration purposes only and does not imply any limitation. Communication network 100 may include any suitable number of devices configured to implement the example embodiments of the present disclosure. Although not shown, it should be understood that one or more additional devices and connections may be deployed in communication network 100.

[0045] Communications in the communication environment 100 may be implemented according to any suitable communication protocol, including, but not limited to, first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), fifth generation (5G), sixth generation (6G), etc. cellular communication protocols, wireless local area network communication protocols (such as those used in the Institute of Electrical and Electronics Engineers (IEEE) 802.11, etc.), and / or any other currently known or later developed protocols. In addition, communications may utilize any suitable wireless communication technology, including, but not limited to, code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), frequency division duplex (FDD), time division duplex (TDD), multiple input multiple output (MIMO), orthogonal frequency division multiplexing (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM), and / or any other currently known or later developed technology. Working principle and example communication signaling

[0046] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0047] Now refer to Figure 2 , which shows a signaling diagram for connected mode mobility in an NES cell according to some example embodiments of the present disclosure. Figure 2 As shown, process 200 involves terminal device 110 and network device 120. For discussion purposes, reference is made to Figure 1 Let's describe the signaling flow 200.

[0048] As previously described, terminal device 110 may be in RRC_CONNECTED mode and served in cell 12. Network device 120 supports NES functionality. Therefore, cell 12 provided by network device 120 may operate in at least one NES state. In some cases, cell 12 may switch between more than one NES state. Additionally, network device 120 may control cell 12 to be turned off or prohibited from being used by NES UEs.

[0049] In some example embodiments, the network device 120 may transmit (205) a configuration of at least one CHO event to the terminal device 110. The at least one CHO event is configured for at least one candidate cell, such as, Figure 1 The cells 14 to 18 are shown. In this case, the candidate cells 14 to 18 can be prepared for potential HO from the serving cell 12.

[0050] At least one CHO event may be triggered based on a change in the operating state of the serving cell 12. For example, the at least one CHO event may be triggered based on a target operating state of the serving cell 12. Such configuration of the at least one CHO event may be indicated, for example, via an RRC reconfiguration message. In the context of the embodiments, the target operating state may refer to one of the following: an off state, a disabled state, an NES state, etc.

[0051] In some example embodiments, the at least one CHO event may include an event triggerHObasedOnNES that triggers a handover based on NES.

[0052] In some example embodiments, the network device 120 may transmit (210) a configuration of a cell selection rule. The cell selection rule may be used in a case where none of the CHO events configured for at least one candidate cell satisfies the CHO condition. It should be noted that the concept of "cell selection rule" is different from the concept of "radio quality criterion". The concept of cell selection rule indicates the selection of a target cell via a reestablishment or CHO procedure based on a change in the operating state of the serving cell to a target operating state, while the concept of radio quality criterion is specified by at least one of the following factors: signal strength, signal quality, PLMN selection, service type, etc.

[0053] It should be understood that, for ease of description, in the example embodiments, cell selection rules are described as being configured separately from CHO events. However, in some other example embodiments, such cell selection rules may be configured as part of a CHO event, or be considered as one of the CHO events, but be used when the remaining configured CHO events do not meet the CHO conditions. Therefore, the present disclosure is not limited in this respect.

[0054] In case of a change of operating state, the network device 120 transmits 215 an indication regarding the change of operating state of the serving cell 12. The indication triggers at least one CHO event at the terminal device 110. Such an indication may be indicated, for example, via a NESState indication.

[0055] In some example embodiments, the indication related to the change in the operating state of the serving cell 12 may be a first indication indicating that the operating state is changed to the off state. For example, when the cell 12 is off, the network device 120 may transmit the first indication to the terminal device 110.

[0056] In some example embodiments, the indication related to the change in the operating state of the serving cell 12 may be a second indication indicating that the operating state has changed to a target NES state. For example, when the cell changes to a certain NES state, the network device 120 may transmit the second indication to the terminal device 110.

[0057] In some example embodiments, the indication related to the change in the operating state of serving cell 12 may be a third indication indicating that the operating state has changed to a barred state. For example, if cell 12 is barred for UE, network device 120 may transmit the third indication to terminal device 110.

[0058] After determining the change in the operating state based on the indication, the terminal device 110 determines (220) whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event. If the at least one CHO event satisfies the CHO condition, the terminal device 110 may perform a CHO from the serving cell 12 to the corresponding candidate cell configured with the CHO event. For example, if the CHO event configured for cell 14 among the candidate cells 14 to 18 satisfies the CHO condition, the terminal device 110 may perform a CHO from the serving cell 12 to the target cell 14.

[0059] Otherwise, if none of the CHO events configured for at least one candidate cell satisfies the CHO condition, the terminal device 110 selects (225) a target cell based on the cell selection rule.

[0060] In some example embodiments, if none of the CHO events configured for at least one candidate cell meet the CHO conditions, the terminal device 110 may declare a radio link failure (RLF) based on the cell selection rules. Accordingly, the terminal device 110 may trigger an RRC reestablishment procedure. The terminal device 110 may then select a target cell via the reestablishment procedure.

[0061] In this case, the UE may perform RRC re-establishment immediately or with a small delay, for example by declaring RLP, which will trigger UE cell selection and RRC re-establishment procedures. As an option, in this case, the RLF cause may be set to "HO failure".

[0062] Additionally or alternatively, the cell selection rule may further include prioritizing at least one candidate cell configured with a CHO event during the reestablishment process. Thus, when performing reestablishment, the terminal device 110 may prioritize candidate cells 14 to 18 configured with CHO because these cells have been prepared by the network.

[0063] In some example embodiments where none of the CHO events configured for at least one candidate cell meet the CHO condition, terminal device 110 may determine whether at least one CHO event configured for at least one candidate cell meets a radio quality criterion. In embodiments of the present disclosure, the radio quality criterion is used to assess the radio quality of a cell. In particular, radio quality may be characterized by at least one of the following factors: signal strength, signal quality, PLMN selection, service type, etc. It should be understood that the radio quality criterion may or may not be part of the cell selection rules.

[0064] If at least one CHO event configured for at least one candidate cell satisfies a radio quality criterion, the terminal device 110 may perform a CHO to one of the at least one candidate cell.

[0065] In this way, if none of the configured conditions are met, the UE falls back to treating the cell selection threshold as the CHO condition threshold. If at least one candidate cell (e.g., cell 18) configured with a CHO event meets the radio quality criteria, the terminal device 110 can select that cell (e.g., cell 18) as the target cell and perform CHO to the target cell. Additionally or alternatively, the UE can also indicate or report a successful CHO to the target cell 18 without the CHO conditions being met. For example, such an indication or report can be transmitted in an RRC ReconfigurationComplete message.

[0066] In some example embodiments, re-establishment or CHO with a cell selection threshold may be limited to situations where the NES state is changed to switch off the cell 12 or the cell 12 is indicated as being barred for the terminal device 110. For other NES state changes, the terminal device 110 may still remain in the serving cell 12 if the CHO conditions are not met.

[0067] In some example embodiments, the network may configure a list of cells or frequencies that should be prioritized for cell selection when the CHO condition is not met. To this end, network device 120 may transmit at least one of a configuration of a candidate cell list or a configuration of a candidate frequency list that will be prioritized for cell selection when the CHO condition is not met. The target cell is selected from the candidate cell list or is associated with a candidate frequency in the candidate frequency list. Furthermore, the candidate cell list and / or the candidate frequency list may be event-specific.

[0068] To implement a CHO event triggered based on an indication related to an operational state change (e.g., an NES state change or cell barring), a new event triggered based on an NES state change or cell barring indication may be added, or alternatively, at least one additional condition may be attached to an existing event. An example extension for an event is shown below. It should be understood that the example extension is also applicable to any event. Table 1. Example events and / or conditions

[0069] The example trigger shown above may be configured for an event triggerHObasedOnNES, which will be triggered if the UE receives an NES indication and some of the candidate cells meet all criteria (eg, radio criteria).

[0070] It may happen that even if the serving cell 12 changes to the "NES state", there may be no event that triggers CHO. However, it is not reasonable to remain on the current cell. In this case, the terminal device 110 can perform a forced RRC reestablishment. The configuration can also be event-specific, that is, RRC reestablishment will only be triggered by the terminal device 110 when a specific CHO event is configured with the parameters in the above example shown in Table 1 (see triggerReestablishment).

[0071] According to some example embodiments of the present disclosure, a solution for connected mode mobility is provided. This solution enables a connected mode UE to undergo handover after its serving cell has been deactivated. In other words, the mobility of a connected mode UE is independent of changes in the operating state of the serving cell. Consequently, UE-autonomous mobility enables faster cell deactivation and avoids the signaling required for individual handovers for each UE.

[0072] It should be understood that some steps in process 200 are optional or can be omitted, and the order of the steps is given for illustrative purposes. Therefore, the embodiments of the present disclosure are not limited in this respect.

[0073] An example description of an embodiment of the present disclosure and possible standardization impacts and information models are as follows. However, it should be understood that the details, values, and configurations in the following description are only example implementations and are not intended to limit the embodiments of the present disclosure. Example Method

[0074] Figure 3FIG2 shows a flow chart of a method 300 implemented at a terminal device according to some example embodiments of the present disclosure. For example, the terminal device may include a UE. For the purpose of discussion, Figure 1 Method 300 is described from the perspective of the terminal device 110 in FIG.

[0075] At block 310, the terminal device 110 receives an indication from the network device 120 regarding a change in the operating state of the serving cell 12. The indication may trigger at the terminal device 110 at least one CHO event.

[0076] In some example embodiments, at least one CHO event may be configured by the network. In these embodiments, terminal device 110 may receive a configuration of at least one CHO event configured for at least one candidate cell from network device 120. The at least one CHO event configured for at least one candidate cell may be triggered based on a target operating state of serving cell 12.

[0077] In some example embodiments, terminal device 110 may receive a configuration of a cell selection rule from network device 120. If none of the CHO events configured for at least one candidate cell satisfies the CHO condition, the cell selection rule is used.

[0078] In some example embodiments, the indication related to the change in the operating state of the serving cell 12 may include at least one of the following: a first indication indicating that the operating state is changed to an off state, a second indication indicating that the operating state is changed to a target network energy saving state, or a third indication indicating that the operating state is changed to a disabled state.

[0079] At block 320 , the terminal device 110 determines whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event.

[0080] At block 330 , based on determining that none of the CHO events configured for at least one candidate cell satisfies the CHO condition, the terminal device 110 selects a target cell based on a cell selection rule.

[0081] In some example embodiments, the cell selection rules may include rules for selecting a target cell via one of a reestablishment or CHO procedure based on the operating state changing to a target operating state for the serving cell 12. In this case, the target operating state may include one of the following: an off state, a barred state, a target NES state.

[0082] In some example embodiments, the rules for selecting the target cell include: triggering RRC re-establishment based on determining that none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and selecting the target cell via the re-establishment procedure.

[0083] In some example embodiments, the rules for selecting the target cell further include: declaring a radio link failure and triggering a re-establishment procedure based on determining that none of the CHO events configured for at least one candidate cell satisfies a CHO condition.

[0084] In some example embodiments, the cell selection rules further comprise prioritizing at least one candidate cell during a reestablishment process.

[0085] In some example embodiments, the rules for selecting a target cell include: determining whether at least one CHO event configured for at least one candidate cell meets a radio quality criterion based on determining that none of the CHO events configured for at least one candidate cell meets a CHO condition; and performing CHO to one of the at least one candidate cell based on determining that the at least one candidate cell meets the radio quality criterion.

[0086] In some example embodiments, method 300 may further include transmitting a report of a successful CHO to the target cell to network device 120 without satisfying the CHO conditions.

[0087] In some example embodiments, method 300 may further include receiving, from network device 120, at least one of a configuration of a candidate cell list or a configuration of a candidate frequency list, at least one of the candidate cell list or the candidate frequency list to be prioritized for cell selection due to failure to meet the CHO condition, wherein the target cell is selected from the candidate cell list or is associated with a candidate frequency in the candidate frequency list.

[0088] In some example embodiments, the at least one CHO event may include an event triggerHObasedOnNES for triggering handover based on network energy saving.

[0089] In some example embodiments, the terminal device 110 may be in RRC_CONNECTED mode.

[0090] Figure 4 FIG2 shows a flow chart of an example method 400 implemented at a network device according to some example embodiments of the present disclosure. For example, the network device may include a gNB. For the purpose of discussion, Figure 1 Method 400 is described from the perspective of network device 120 in FIG.

[0091] At 410, the network device 120 transmits the configuration of the cell selection rule to the terminal device 110 in the serving cell 12 provided by the network device 120. The cell selection rule is used when none of the CHO events configured for at least one candidate cell satisfies the CHO condition.

[0092] At 420 , the network device 120 transmits an indication regarding a change in the operating state of the serving cell to the terminal device 110 . The indication triggers at least one CHO event at the terminal device 110 .

[0093] In some example embodiments, method 400 may further include transmitting a configuration of at least one CHO event configured for at least one candidate cell, the at least one CHO event configured for the at least one candidate cell being triggered based on a target operating state of the serving cell.

[0094] In some example embodiments, the indication related to the change in the operating state of the serving cell may include at least one of the following: a first indication indicating that the operating state is changed to an off state, a second indication indicating that the operating state is changed to a target network energy saving state, or a third indication indicating that the operating state is changed to a prohibited state.

[0095] In some example embodiments, the cell selection rule may indicate at least one of: selecting the target cell via a reestablishment procedure based on a change in the operating state of the serving cell to the target operating state; selecting the target cell via a CHO procedure based on a change in the operating state of the serving cell to the target operating state and a radio quality criterion; and during the selection of the target cell, giving priority to at least one candidate cell configured with a CHO event.

[0096] In some example embodiments, the target operating state may include one of: an off state, a disabled state, a target NES state.

[0097] In some example embodiments, the method 400 may further comprise receiving a report of a successful CHO to the target cell from the terminal device 110 without the CHO condition being satisfied.

[0098] In some example embodiments, the method 400 may further include transmitting to the terminal device 110 at least one of a configuration of a candidate cell list and / or a configuration of a candidate frequency list, wherein at least one of the candidate cell list or the candidate frequency list will be preferentially used for cell selection due to failure to meet the CHO condition, wherein the target cell is selected from the candidate cell list or is associated with a candidate frequency in the candidate frequency list.

[0099] In some example embodiments, the at least one CHO event includes an event triggerHObasedOnNES for triggering handover based on network energy saving.

[0100] In some example embodiments, a first device (eg, Figure 1The terminal device 110 in the embodiment may include components for performing the corresponding operations of the method 300. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit or a software module. The first device may be implemented as or included in Figure 1 In the terminal device 110.

[0101] In some example embodiments, the first device includes: a component for receiving an indication related to a change in the operating state of a serving cell from a second device, indicating that at least one conditional handover (CHO) event is triggered at the first device; a component for determining whether at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; and a component for selecting a target cell based on a cell selection rule based on determining that none of the CHO events configured for at least one candidate cell satisfies the CHO condition.

[0102] In some example embodiments, the first apparatus further comprises means for receiving, from the second apparatus, configuration of at least one CHO event configured for at least one candidate cell, wherein the at least one CHO event configured for the at least one candidate cell is triggered based on a target operating state of the serving cell.

[0103] In some example embodiments, the first apparatus further comprises means for receiving configuration of a cell selection rule from the second apparatus, the cell selection rule being used if none of the CHO events configured for the at least one candidate cell satisfies the CHO condition.

[0104] In some example embodiments, the indication related to the change in the operating state of the serving cell includes at least one of: a first indication indicating that the operating state is changed to an off state, a second indication indicating that the operating state is changed to a target network energy saving state, or a third indication indicating that the operating state is changed to a prohibited state.

[0105] In some example embodiments, the cell selection rules include rules for selecting a target cell via one of a reestablishment or CHO procedure based on a change in operating state to a target operating state for the serving cell, wherein the target operating state includes one of the following: an off state, a barred state, a target network energy saving state.

[0106] In some example embodiments, the rules for selecting the target cell further include: triggering RRC re-establishment based on determining that none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and selecting the target cell via the re-establishment process.

[0107] In some example embodiments, the rules for selecting the target cell further include: declaring a radio link failure and triggering a re-establishment procedure based on determining that none of the CHO events configured for at least one candidate cell satisfies a CHO condition.

[0108] In some example embodiments, the cell selection rules further comprise prioritizing at least one candidate cell during a reestablishment process.

[0109] In some example embodiments, the rules for selecting a target cell include: determining whether at least one CHO event configured for at least one candidate cell satisfies a radio quality criterion based on determining that none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and performing CHO to one of the at least one candidate cell based on determining that the at least one candidate cell satisfies the radio quality criterion.

[0110] In some example embodiments, the first apparatus further comprises means for transmitting a report of a successful CHO of the target cell to the second apparatus without satisfying the CHO condition.

[0111] In some example embodiments, the first apparatus further comprises: means for receiving at least one of a configuration of a candidate cell list or a configuration of a candidate frequency list from the second apparatus, at least one of the candidate cell list or the candidate frequency list to be prioritized for cell selection due to failure to satisfy the CHO condition, wherein the target cell is selected from the candidate cell list or is associated with a candidate frequency in the candidate frequency list.

[0112] In some example embodiments, the at least one CHO event includes an event triggerHObasedOnNES for triggering handover based on network energy saving.

[0113] In some example embodiments, the first apparatus comprises a terminal device in RRC_CONNECTED mode.

[0114] In some example embodiments, a second device (eg, Figure 1 The network device 120 in the embodiment may include components for performing the corresponding operations of the method 400. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit or a software module. The second device may be implemented as or included in Figure 1 In the network device 120.

[0115] In some example embodiments, the second device includes: a component for transmitting a configuration of a cell selection rule to a first device in a serving cell provided by the second device, wherein the cell selection rule is used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and a component for transmitting an indication related to a change in an operating state of the serving cell to the first device, indicating that at least one CHO event is triggered at the first device.

[0116] In some example embodiments, the second apparatus further comprises means for transmitting a configuration of at least one CHO event configured for at least one candidate cell to the first apparatus, the at least one CHO event configured for the at least one candidate cell being triggered based on a target operating state of the serving cell.

[0117] In some example embodiments, the indication related to the change in the operating state of the serving cell includes at least one of: a first indication indicating that the operating state is changed to an off state, a second indication indicating that the operating state is changed to a target network energy saving state, or a third indication indicating that the operating state is changed to a prohibited state.

[0118] In some example embodiments, the cell selection rule indicates at least one of: selecting the target cell via a reestablishment procedure based on a change in an operating state of the serving cell to a target operating state, selecting the target cell via a CHO procedure based on a change in an operating state of the serving cell to a target operating state and a radio quality criterion, and during the selection of the target cell, giving priority to at least one candidate cell configured with a CHO event.

[0119] In some example embodiments, the target operating state comprises one of: an off state, a disabled state, a target network energy saving state.

[0120] In some example embodiments, the second apparatus further comprises means for receiving a report of a successful CHO of the target cell from the first apparatus without satisfying the CHO condition.

[0121] In some example embodiments, the second apparatus further comprises: means for transmitting at least one of a configuration of a candidate cell list and / or a configuration of a candidate frequency list to the first apparatus, at least one of the candidate cell list or the candidate frequency list to be prioritized for cell selection due to failure to meet the CHO condition, wherein the target cell is selected from the candidate cell list or is associated with a candidate frequency in the candidate frequency list.

[0122] In some example embodiments, the at least one CHO event includes an event triggerHObasedOnNES for triggering handover based on network energy saving.

[0123] Figure 5 is a simplified block diagram of a device 500 suitable for implementing an example embodiment of the present disclosure. The device 500 may be provided to implement an electronic device, such as Figure 1 The terminal device 110 and the network devices 112 to 130 are shown. As shown in the figure, the device 500 includes one or more processors 510, one or more memories 520 coupled to the processors 510, and one or more communication modules 540 coupled to the processors 510.

[0124] The communication module 540 is configured for bidirectional communication. The communication module 540 has one or more communication interfaces to facilitate communication with one or more other modules or devices. A communication interface may represent any interface necessary to communicate with other network elements. In some example embodiments, the communication module 540 may include at least one antenna.

[0125] As non-limiting examples, processor 510 can be of any type suitable for a local technology network and can include, as non-limiting examples, one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 500 can have multiple processors, such as application-specific integrated circuit chips, that are time-slave to a clock synchronized with a main processor.

[0126] The memory 520 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 524, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact disks (CDs), digital video disks (DVDs), optical disks, laser disks, and other magnetic and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 522 and other volatile memories that will not be maintained during a power outage.

[0127] Computer program 530 includes computer-executable instructions that are executed by the associated processor 510. The instructions of program 530 may include instructions for performing the operations / actions of some example embodiments of the present disclosure. Program 530 may be stored in a memory, such as ROM 524. Processor 510 may perform any suitable actions and processes by loading program 530 into RAM 522.

[0128] The exemplary embodiments of the present disclosure may be implemented with the aid of program 530, so that device 500 may perform the operations described in reference to Figures 1 to 4 Any process of the present disclosure discussed. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0129] In some example embodiments, program 530 may be tangibly included in a computer-readable medium that may be included in device 500 (such as in memory 520) or other storage device accessible to device 500. Device 500 may load program 530 from the computer-readable medium to RAM 522 for execution. In some example embodiments, the computer-readable medium may include any type of non-transitory storage medium, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc. The term "non-transitory" as used herein is a limitation on the medium itself (i.e., tangible, not a signal), not on data storage persistence (e.g., RAM vs. ROM).

[0130] Figure 6 An example of a computer readable medium 600 is shown, which may be in the form of a CD, DVD, or other optical storage disc.Computer readable medium 600 stores program 530 thereon.

[0131] In general, various embodiments of the present disclosure may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that the blocks, devices, systems, techniques, or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or a controller or other computing device, or some combination thereof.

[0132] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer-readable medium (such as a non-transitory computer-readable medium). The computer program product includes computer-executable instructions, such as those included in a program module, which are executed by a device on a target physical or virtual processor to perform any of the methods described above. Typically, a program module includes routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. The functionality of the program modules can be combined or split between program modules as needed in various embodiments. The machine executable instructions for the program modules can be located in a local or remote storage medium.

[0133] The program code for implementing the method of the present disclosure can be written in any combination of one or more programming languages. The program code can be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code can be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0134] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform the above-mentioned various processes and operations. Examples of carriers include signals, computer-readable media, etc.

[0135] The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media include an electrical connection having one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0136] In addition, although operations are described in a particular order, it should not be understood that it is required to perform these operations in the particular order shown or in sequence, or to perform all of the operations shown in order to achieve the desired result. In some cases, multi-tasking and parallel processes can be advantageous. Similarly, although several specific implementation details are included in the above discussion, they should not be regarded as limitations on the scope of this disclosure, but should be used as descriptions of features that can be specific to certain embodiments. Unless expressly stated otherwise, certain features described in the context of a separate embodiment can also be implemented in combination in a single embodiment. On the contrary, unless expressly stated otherwise, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0137] Although the disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A device comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receiving an indication from a network device relating to a change in an operational state of a serving cell, the indication triggering at least one conditional handover (CHO) event at the apparatus; determining whether the at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; as well as Based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition, a target cell is selected based on a cell selection rule.

2. The apparatus of claim 1 , wherein the apparatus is further configured to: A configuration of the at least one CHO event configured for the at least one candidate cell is received from the network device, wherein the at least one CHO event configured for the at least one candidate cell is triggered based on a target operating state of the serving cell.

3. The apparatus of claim 1 , wherein the apparatus is further configured to: The configuration of the cell selection rule is received from the network device, and the cell selection rule is used if none of the CHO events configured for the at least one candidate cell satisfies the CHO condition.

4. The apparatus of claim 1 , wherein the indication related to the change in the operating state of the serving cell comprises at least one of: a first indication indicating that the operating state is changed to a closed state, a second indication indicating that the operating state is changed to a target network energy-saving state, or A third indication indicates that the operating state is changed to a disabled state.

5. The apparatus of claim 1 , wherein the cell selection rules comprise rules for selecting the target cell via one of a reestablishment or a CHO procedure based on the operating state changing to a target operating state for the serving cell, The target operating state includes one of the following: a closed state, a disabled state, and a target network energy-saving state.

6. The apparatus of claim 5, wherein the rule for selecting the target cell comprises: triggering RRC re-establishment based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition; as well as The target cell is selected via the reestablishment process.

7. The apparatus according to claim 6, wherein the rule for selecting the target cell further comprises: Based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition, a radio link failure is declared, and the re-establishment process is triggered.

8. The apparatus according to claim 6, wherein the cell selection rule further comprises: The at least one candidate cell is prioritized during the reestablishment process.

9. The apparatus according to any one of claims 1 to 5, wherein the rule for selecting the target cell comprises: determining whether the at least one CHO event configured for the at least one candidate cell satisfies a radio quality criterion based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition; Based on determining that the at least one candidate cell satisfies the radio quality criterion, a CHO is performed to one of the at least one candidate cell.

10. The apparatus of claim 9, wherein the apparatus is further configured to: In a case where the CHO condition does not need to be met, a report of a successful CHO of the target cell is transmitted to the network device.

11. The apparatus according to any one of claims 1 to 5, wherein the apparatus is further configured to perform: receiving, from the network device, at least one of a configuration of a candidate cell list or a configuration of a candidate frequency list, wherein at least one of the candidate cell list or the candidate frequency list is to be prioritized for cell selection due to failure to meet a CHO condition, wherein the target cell is selected from the candidate cell list or is associated with a candidate frequency in the candidate frequency list. 12 . The apparatus according to claim 1 , wherein the at least one CHO event comprises an event triggerHObasedOnNES for triggering handover based on network energy saving.

13. An apparatus according to any one of claims 1 to 12, wherein the apparatus comprises a terminal device in RRC_CONNECTED mode.

14. An apparatus comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: Transmitting a configuration of a cell selection rule to a terminal device in a serving cell provided by the apparatus, the cell selection rule being used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; as well as An indication relating to a change in the operating state of the serving cell is transmitted to the terminal device, the indication triggering at least one CHO event at the terminal device.

15. The apparatus of claim 14, wherein the apparatus is further configured to: A configuration of the at least one CHO event configured for the at least one candidate cell is transmitted to the terminal device, where the at least one CHO event configured for the at least one candidate cell is triggered based on a target operating state of the serving cell.

16. The apparatus according to claim 14 or claim 15, wherein the indication related to the change in the operating state of the serving cell comprises at least one of the following: a first indication indicating that the operating state is changed to a closed state, a second indication indicating that the operating state is changed to a target network energy-saving state, or A third indication indicates that the operating state is changed to a disabled state.

17. The apparatus of claim 14, wherein the cell selection rule indicates at least one of the following: selecting a target cell via a reestablishment process based on the operating state of the serving cell changing to a target operating state, selecting the target cell via a CHO procedure based on the change of the operating state of the serving cell to the target operating state and a radio quality criterion, During the selection of the target cell, at least one candidate cell configured with the CHO event is given priority.

18. The apparatus of claim 17, wherein the target operating state comprises one of the following: an off state, a disabled state, and a target network energy saving state.

19. The apparatus of claim 17, wherein the apparatus is further configured to: A report of a successful CHO to the target cell is received from the terminal device without satisfying the CHO condition.

20. The apparatus of claim 17, wherein the apparatus is further configured to: Transmitting at least one of the configuration of the candidate cell list and / or the configuration of the candidate frequency list to the terminal device, wherein the candidate cell list or at least one of the candidate frequency list will be preferentially used for cell selection due to failure to meet the CHO condition, wherein the target cell is selected from the candidate cell list or is associated with a candidate frequency in the candidate frequency list. 21 . The apparatus according to claim 14 , wherein the at least one CHO event comprises an event triggerHObasedOnNES for triggering handover based on network energy saving.

22. A method comprising: receiving, at a terminal device, from a network device, an indication relating to a change in an operating state of a serving cell, the indication triggering at least one conditional handover (CHO) event at the terminal device; determining whether the at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; as well as Based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition, a target cell is selected based on a cell selection rule.

23. A method comprising: Transmitting, at a network device, a configuration of a cell selection rule to a terminal device in a serving cell provided by the network device, wherein the cell selection rule is used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; as well as An indication relating to a change in the operating state of the serving cell is transmitted to the terminal device, the indication triggering at least one CHO event at the terminal device.

24. A first device comprising: means for receiving an indication from a second apparatus relating to a change in an operational state of a serving cell, said indication triggering at least one conditional handover (CHO) event at said first apparatus; means for determining whether the at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; as well as A component for selecting a target cell based on a cell selection rule based on determining that none of the CHO events configured for the at least one candidate cell meets the CHO condition.

25. A second device comprising: means for transmitting a configuration of a cell selection rule to a first apparatus in a serving cell provided by the second apparatus, wherein the cell selection rule is used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; as well as Means for transmitting an indication related to a change in an operational state of the serving cell to the first apparatus, the indication triggering at least one CHO event at the first apparatus.

26. A computer-readable medium comprising program instructions for causing an apparatus to execute: receiving an indication from a network device relating to a change in an operational state of a serving cell, the indication triggering at least one conditional handover (CHO) event at the apparatus; determining whether the at least one CHO event configured for at least one candidate cell satisfies a CHO condition associated with the CHO event; as well as Based on determining that none of the CHO events configured for the at least one candidate cell satisfies the CHO condition, a target cell is selected based on a cell selection rule.

27. A computer-readable medium comprising program instructions for causing an apparatus to execute: Transmitting a configuration of a cell selection rule to a terminal device in a serving cell provided by the apparatus, the cell selection rule being used when none of the CHO events configured for at least one candidate cell satisfies a CHO condition; and An indication relating to a change in the operating state of the serving cell is transmitted to the terminal device, the indication triggering at least one CHO event at the terminal device.

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