Low layer trigger mobility

Abstract

The invention relates to low layer triggered mobility (LTM) mobility. A method, an apparatus, and a computer program are described. The method comprises receiving, from a network node, a configuration comprising a list of candidate target cells for LTM handover. For at least one candidate target cell in the list of candidate target cells, an evaluation of a reception timing difference between a signal received from the serving cell and a signal received from the at least one candidate target cell is performed, and a determination is further performed based on the RTD and a predetermined time window, the determination relates to an ability of the apparatus to perform layer 1 measurements for at least one candidate target cell. The method then causes transmission of information about the determination to the network node.

Description

Technical Field

[0001] Various example embodiments relate to wireless communication systems, and more specifically to facilitating mobility within such wireless communication systems. Background Technology

[0002] When a user equipment (UE) moves within a wireless communication system, it can move within cells that include a radio coverage area supported by one or more network access nodes. The ability of a UE to maintain effective communication with the wireless communication system while moving through an area of ​​radio coverage is commonly referred to as mobility. Layer 1 or Layer 2 triggered mobility (sometimes called lower-layer triggered mobility) is increasingly seen as a way to reduce latency, overhead, and downtime associated with UE movement between different cells. Summary of the Invention

[0003] The independent claims define the scope of protection sought by the various exemplary embodiments of the invention. Exemplary embodiments and features (if any) described in this specification that are not within the scope of the independent claims are to be interpreted as examples that aid in understanding the various embodiments of the invention.

[0004] According to various, but not necessarily all, exemplary embodiments of the present invention, an apparatus is provided comprising: 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 configuration from a network node, the configuration including a list of candidate target cells for triggering mobility LTM handover at a lower layer; for at least one candidate target cell in the list of candidate target cells, perform an evaluation of a reception timing difference (RTD) between a signal received from the serving cell and a signal received from the at least one candidate target cell; perform a determination based on the RTD and a predetermined time window, wherein the determination is related to the apparatus's ability to perform Layer 1 (L1) measurements for the at least one candidate target cell; and cause information regarding the determination to be transmitted to the network node.

[0005] In Low Layer Triggered Mobility (LTM), which may be referred to as Layer 1 / L2 (L1 / L2) triggered mobility, the target cell selected for handover is based on low-layer measurements performed at the device (which may be a UE). Some devices only support low-layer measurements where the RTD and a predetermined time window have a specific relationship, such as in some embodiments where the RTD is less than or equal to the predetermined time window. This depends on the device, and the network may not be aware of the device's capabilities in this regard and therefore may not know which low-layer measurements are reliable and which are unreliable. To address this potential problem, the device evaluates the RTD of one or more candidate cells and determines its ability to reliably perform these low-layer measurements based on the RTD and the predetermined time window, and provides this information to the network.

[0006] For the purposes of this application, LTM and L1 / L2 trigger mobility handover are interchangeably used to represent handover triggered by lower-level measurements.

[0007] In some example embodiments, the predetermined time window includes the length of the cyclic prefix (CP).

[0008] In some example embodiments, the information is caused to be sent in at least one of the following: L1 measurement report transmission; L3 measurement report transmission; or a transmission separate from any L3 or L1 measurement report transmission.

[0009] In some example embodiments, the transmission of information about the determination includes one of the following: causing the information to be transmitted only in the first L1 and / or the first L3 measurement report; causing the information to be transmitted in a predetermined number of L1 and / or L3 measurement reports; or causing the information to be transmitted in all L1 and / or L3 measurement reports until the LTM switch is completed.

[0010] In some example embodiments, the apparatus is configured to perform the determination based on the RTD and a predetermined time window by: determining candidate target cells whose RTD is less than or equal to the predetermined time window; and the information regarding the determination includes an indication of candidate cells whose RTD is less than or equal to the predetermined time window.

[0011] In some example embodiments, the apparatus is configured to perform the determination based on the RTD and a predetermined time window by: determining candidate target cells whose RTD is greater than the predetermined time window; and the information regarding the determination includes an indication of candidate cells whose RTD is greater than the predetermined time window.

[0012] In some example embodiments, the device is configured to transmit an indication of whether or not the device supports L1 measurement based on whether the RTD is greater than, equal to, or less than a predetermined time window.

[0013] In some example embodiments, the device is configured to cause the transmission of an indication that the device supports L1 measurement when the RTD is less than or equal to a predetermined time window.

[0014] In some example embodiments, the device is configured to cause the transmission of an indication that the device does not support L1 measurement when the RTD is greater than a predetermined time window.

[0015] In some example embodiments, the apparatus is also configured to: receive from a network node an instruction regarding the following: for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to a predetermined time window; and based on the received instruction, skip execution for at least one candidate target cell for which the RTD is assumed to be less than or equal to the predetermined time window.

[0016] In some example embodiments, at least one candidate target cell with an RTD that is assumed to be less than or equal to a predetermined time window is co-located with the serving cell.

[0017] In some example embodiments, the device is also configured to perform L1 measurements on a set of candidate target cells whose RTD is less than or equal to a predetermined time window.

[0018] In some example embodiments, the device is also configured to receive a configuration for performing L1 measurements only for the candidate cell set.

[0019] In some example embodiments, the device is also configured to send an L1 measurement report, including the L1 measurement performed, to a network node.

[0020] In some example embodiments, the apparatus is also configured to: update the evaluation of the RTD, update the determination, and cause information about the updated determination to be transmitted to the network node.

[0021] According to various, but not necessarily all, exemplary embodiments of the present invention, a method is provided to be performed at a device, the method comprising: receiving configuration from a network node, the configuration including a list of candidate target cells for triggering mobility LTM handover at a lower layer; for at least one candidate target cell in the list of candidate target cells, performing an evaluation of a reception timing difference (RTD) between a signal received from a serving cell and a signal received from the at least one candidate target cell; performing a determination based on the RTD and a predetermined time window, wherein the determination is related to the device’s ability to perform layer 1 (L1) measurements for the at least one candidate target cell; and causing information about the determination to be transmitted to the network node.

[0022] In some example embodiments, the predetermined time window includes the length of the cyclic prefix (CP).

[0023] In some example embodiments, this information is sent in the L1 measurement report transmission.

[0024] Alternatively and / or additionally, this information may be sent in the L3 measurement report transmission.

[0025] Sending this information in periodic measurement reports sent to the network can be an effective and signaling-efficient way to provide this information.

[0026] Alternatively and / or additionally, this information may be sent in a transmission separate from any Layer 3 or Layer 1 measurement report transmission.

[0027] This can be a more flexible arrangement compared to combining the indication with L1 or L3 measurement reports. However, it increases the number of transmissions performed by the UE.

[0028] In some example embodiments, the transmission of information about the determination includes one of the following: causing the information to be transmitted only in the first L1 and / or the first L3 measurement report; causing the information to be transmitted in a predetermined number of L1 and / or L3 measurement reports; or causing the information to be transmitted in all L1 and / or L3 measurement reports until the LTM switch is completed.

[0029] In some example embodiments, performing a determination based on RTD and a predetermined time window includes: determining candidate target cells whose RTD is less than or equal to the predetermined time window; and wherein the information regarding the determination includes an indication of candidate cells whose RTD is less than or equal to the predetermined time window.

[0030] In some example embodiments, performing a determination based on RTD and a predetermined time window includes: determining candidate target cells whose RTD is greater than the predetermined time window; and wherein information about the determination includes an indication of candidate cells whose RTD is greater than the predetermined time window.

[0031] Whether the device can reliably perform L1 measurements can be determined by whether the RTD is less than or equal to the predetermined time window. Therefore, it is possible to determine whether this is the case and indicate this to the network.

[0032] In some example embodiments, the indication is a list of detected candidate target cells, or a bitmap of candidate cells in the indication list, which can distinguish cells in the list that have an RTD greater than a predetermined time window and cells that have an RTD less than or equal to the predetermined time window.

[0033] In some example embodiments, the method includes transmitting an indication of whether the device supports or does not support L1 measurement based on whether the RTD is greater than, equal to, or less than a predetermined time window.

[0034] In some example embodiments, the method includes: causing the device to transmit an indication that it supports L1 measurement when the RTD is equal to or less than a predetermined time window.

[0035] In some example embodiments, the method includes causing the device to not support the transmission of an indication of L1 measurement when the RTD is greater than a predetermined time window.

[0036] In some example embodiments, the method further includes: receiving from a network node an indication that for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to a predetermined time window; and, based on the received indication, skipping the evaluation of the RTD for at least one candidate target cell for which the RTD is assumed to be less than or equal to the predetermined time window.

[0037] In some example embodiments, at least one candidate target cell with an RTD that is assumed to be less than or equal to a predetermined time window is co-located with the serving cell.

[0038] In some example embodiments, the method includes performing L1 measurements on a set of candidate target cells whose RTD is less than or equal to a predetermined time window.

[0039] In some example embodiments, the method includes receiving a configuration for performing L1 measurements only for the candidate cell set.

[0040] In some example embodiments, the method includes: inducing the transmission of an L1 measurement report, including the performed L1 measurement, to a network node.

[0041] In some example embodiments, the method includes: updating the evaluation of the RTD, updating the determination, and causing information about the updated determination to be transmitted to the network node.

[0042] According to various, but not necessarily all, exemplary embodiments of the present invention, a non-transitory computer-readable medium is provided, the medium comprising program instructions stored thereon, which, when executed by a processor on a device, cause the device to perform at least the following: receiving a configuration from a network node, the configuration including a list of candidate target cells for triggering mobility LTM handover at a lower layer; for at least one candidate target cell in the list of candidate target cells, performing an evaluation of the reception timing difference (RTD) between a signal received from the serving cell and a signal received from the at least one candidate target cell; performing a determination based on the RTD and a predetermined time window, wherein the determination is related to the device's ability to perform layer 1 (L1) measurements for the at least one candidate target cell; and transmitting information about the determination to the network node.

[0043] According to various, but not necessarily all, exemplary embodiments of the invention, a computer program is provided that, when executed by a processor on a device, causes the device to perform at least the following: receiving a configuration from a network node, the configuration including a list of candidate target cells for triggering mobility LTM handover at a lower layer; for at least one candidate target cell in the list of candidate target cells, performing an evaluation of the reception timing difference (RTD) between a signal received from the serving cell and a signal received from the at least one candidate target cell; performing a determination based on the RTD and a predetermined time window, wherein the determination is related to the device's ability to perform layer 1 (L1) measurements for the at least one candidate target cell; and causing information about the determination to be transmitted to the network node.

[0044] The computer program can cause the device to perform optional features related to the above-described method.

[0045] According to various, but not necessarily all, exemplary embodiments of the present invention, an apparatus is provided comprising: means for receiving configuration from a network node, the configuration including a list of candidate target cells for triggering a low-layer mobility LTM handover; means for performing an evaluation of a reception timing difference (RTD) between a signal received from a serving cell and a signal received from the at least one candidate target cell in the candidate target cell list; means for performing a determination based on the RTD and a predetermined time window, wherein the determination is related to the ability of the apparatus to perform layer 1 (L1) measurements for the at least one candidate target cell; and means for inducing the transmission of information regarding the determination to the network node.

[0046] This component can perform optional features associated with the aforementioned device.

[0047] According to various, but not necessarily all, exemplary embodiments of the present invention, an apparatus is provided comprising: circuitry configured to receive configuration from a network node, the configuration including a list of candidate target cells for triggering a low-layer mobility LTM handover; circuitry configured to perform an evaluation of a reception timing difference (RTD) between a signal received from a serving cell and a signal received from the at least one candidate target cell in the candidate target cell list; circuitry configured to perform a determination based on the RTD and a predetermined time window, wherein the determination is related to the apparatus's ability to perform layer 1 (L1) measurements for the at least one candidate target cell; and circuitry configured to cause the transmission of information regarding the determination to the network node.

[0048] The circuit system can be configured to perform optional features associated with the aforementioned device.

[0049] According to various, but not necessarily all, exemplary embodiments of the present invention, an apparatus is provided, the apparatus comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the apparatus to at least perform: inducing the transmission of a configuration to a user equipment (UE), the configuration including a list of candidate target cells for lower-layer triggered mobility (LTM) handover; receiving from the UE information regarding a determination made by the UE for at least one candidate target cell in the list of candidate target cells, wherein the determination is based on a reception timing difference (RTD) between a signal received by the UE from a serving cell and a signal received by the UE from the at least one candidate target cell and a predetermined time window, wherein the determination is related to the UE's ability to perform layer 1 (L1) measurements for the at least one candidate cell; selecting a subset of candidate target cells in the list of candidate target cells based on the received information; and inducing the transmission of an indication of the subset of candidate target cells to the UE.

[0050] In some example embodiments, the predetermined time window includes the length of the cyclic prefix (CP).

[0051] In some example embodiments, the apparatus is also configured to perform: receiving from the UE an L1 measurement report including L1 measurements for the subset; and selecting a target cell for LTM handover based on the L1 measurement report.

[0052] In some example embodiments, the apparatus is also configured to: perform a transmission of an indication of a selected target cell to the UE, the indication being included in a cell handover command.

[0053] In some example embodiments, the subset includes candidate target cells whose RTD is less than or equal to a predetermined time window.

[0054] In some example embodiments, the apparatus is also configured to cause the transmission of an instruction to the UE regarding the following: for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to a predetermined time window.

[0055] In some example embodiments, an indication of at least one candidate target cell having an RTD that is assumed to be less than or equal to a predetermined time window is included in the transmission that also includes this configuration.

[0056] In other embodiments, an indication of at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window is included in a transmission that does not include the candidate target cell configuration.

[0057] In some example embodiments, at least one candidate target cell with an RTD that is assumed to be less than or equal to a predetermined time window is co-located with the serving cell.

[0058] In some example embodiments, the apparatus is also configured to: execute the transmission of instructions to the UE, the instructions being used to skip the evaluation of RTD for at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window.

[0059] In some example embodiments, the apparatus is also configured to: when a subset of candidate cells is selected, reconfigure the candidate target cell list for LTM handover to exclude candidate target cells with an RTD greater than a predetermined time window; and when an indication of a subset of candidate target cells is transmitted to the UE, cause an indication of a reconfigured candidate target cell list to be transmitted to the UE.

[0060] In some example embodiments, the apparatus is also configured to: receive from the UE an indication of a candidate target cell detected by the UE, preferably wherein the indication of the detected candidate target cell is included in the layer 3 measurement report.

[0061] In some example embodiments, the device includes a network node.

[0062] In some example embodiments, the network node includes gNodeB.

[0063] According to various, but not necessarily all, example embodiments of the present invention, a method performed at an apparatus is provided, the method comprising: inducing the transmission of a configuration to a user equipment (UE), the configuration including a list of candidate target cells for lower layer triggered mobility (LTM) handover; receiving from the UE information regarding a determination made by the UE for at least one candidate target cell in the list of candidate target cells, wherein the determination is based on a reception timing difference (RTD) between a signal received by the UE from a serving cell and a signal received by the UE from the at least one candidate target cell and a predetermined time window, wherein the determination is related to the UE's ability to perform layer 1 (L1) measurements for the at least one candidate cell; selecting a subset of candidate target cells in the list of candidate target cells based on the received information; and inducing the transmission of an indication of the subset of candidate target cells to the UE.

[0064] In some example embodiments, the predetermined time window includes the length of the cyclic prefix (CP).

[0065] In some example embodiments, the subset includes candidate target cells whose RTD is less than or equal to a predetermined time window.

[0066] In some example implementations, a subset of candidate target cells may be a subset used by the UE to perform L1 measurements for them.

[0067] In some example embodiments, the subset includes candidate target cells with an RTD greater than a predetermined time window.

[0068] In some example implementations, this subset indicates candidate target cells for which the UE should not perform L1 measurements.

[0069] In some example embodiments, the method further includes: receiving from the UE an L1 measurement report including L1 measurements for the subset; and selecting a target cell for LTM handover based on the L1 measurement report.

[0070] In some example embodiments, the method further includes: inducing the transmission of an indication of the selected target cell to the UE, the indication being included in the cell handover command.

[0071] In some example implementations, the cell handover command is included within the MAC CE transmission.

[0072] In some example embodiments, selecting a target cell includes selecting candidate target cells whose RTD is less than or equal to a predetermined time window.

[0073] In some example implementations, selecting a target cell includes selecting or not selecting candidate target cells whose RTD is greater than a predetermined time window.

[0074] In some example embodiments, the method further includes: inducing the transmission of an indication to the UE that for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to a predetermined time window.

[0075] In some example embodiments, an indication of at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window is included in a transmission that also includes this configuration. In other embodiments, an indication of at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window is included in a transmission that does not include the candidate target cell configuration.

[0076] In some example embodiments, at least one candidate target cell with an RTD that is assumed to be less than or equal to a predetermined time window is co-located with the serving cell.

[0077] In some example embodiments, the method further includes: inducing the transmission of an instruction to the UE to skip the evaluation of the RTD for at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window.

[0078] In some example embodiments, the step of selecting a subset of candidate cells includes: reconfiguring the candidate target cell list for LTM handover to exclude candidate target cells with an RTD greater than a predetermined time window; and the step of causing the transmission of an indication of a subset of candidate target cells to the UE includes causing the transmission of an indication of a reconfigured candidate target cell list to the UE.

[0079] In some example implementations, the candidate target cell list includes eight candidate target cells.

[0080] In some example embodiments, the method further includes receiving from the UE an indication of a candidate target cell detected by the UE, preferably wherein the indication of the detected candidate target cell is included in the layer 3 measurement report.

[0081] According to various, but not necessarily all, exemplary embodiments of the present invention, a non-transitory computer-readable medium is provided, the medium comprising program instructions stored thereon, which, when executed by a processor on an apparatus, cause the apparatus to perform at least the following: receiving a configuration from a network node, the configuration including a list of candidate target cells for triggering a low-layer mobility LTM handover; for at least one candidate target cell in the list of candidate target cells, performing an evaluation of a reception timing difference (RTD) between a signal received from the serving cell and a signal received from the at least one candidate target cell; performing a determination based on the RTD and a predetermined time window, wherein the determination is related to the apparatus's ability to perform layer 1L1 measurements for the at least one candidate target cell; and causing information regarding the determination to be transmitted to the network node.

[0082] According to various, but not necessarily all, exemplary embodiments of the present invention, a computer program is provided that, when executed by a processor on a device, causes the device to perform at least the following: inducing the transmission of a configuration to a user equipment (UE), the configuration including a list of candidate target cells for lower-layer triggered mobility (LTM) handover; receiving from the UE information regarding a determination made by the UE for at least one candidate target cell in the list of candidate target cells, wherein the determination is based on a reception timing difference (RTD) and a predetermined time window between signals received by the UE from the serving cell and signals received by the UE from the at least one candidate target cell, wherein the determination is related to the UE's ability to perform layer 1 (L1) measurements for the at least one candidate cell; selecting a subset of candidate target cells in the list of candidate target cells based on the received information; and inducing the transmission of an indication of the subset of candidate target cells to the UE.

[0083] The computer program can cause the device to perform optional features related to the above-described method.

[0084] According to various, but not necessarily all, example embodiments of the present invention, an apparatus is provided comprising: means for transmitting to a user equipment (UE) a configuration including a list of candidate target cells for lower layer triggered mobility (LTM) handover; means for receiving from the UE information regarding a determination made by the UE for at least one candidate target cell in the list of candidate target cells, wherein the determination is based on a reception timing difference (RTD) between a signal received by the UE from a serving cell and a signal received by the UE from the at least one candidate target cell and a predetermined time window, wherein the determination is related to the UE's ability to perform layer 1 (L1) measurements for the at least one candidate cell; means for selecting a subset of candidate target cells in the list of candidate target cells based on the received information; wherein the means for transmitting is configured to transmit an indication of the subset of candidate target cells to the UE.

[0085] This component can perform optional features associated with the aforementioned device.

[0086] According to various, but not necessarily all, exemplary embodiments of the present invention, an apparatus is provided comprising: circuitry configured to cause a transmission of configuration to a user equipment (UE), the configuration including a list of candidate target cells for lower-layer triggered mobility (LTM) handover; circuitry configured to receive from the UE information regarding a determination made by the UE for at least one candidate target cell in the list of candidate target cells, wherein the determination is based on a reception timing difference (RTD) between a signal received by the UE from a serving cell and a signal received by the UE from the at least one candidate target cell and a predetermined time window, wherein the determination is related to the UE's ability to perform layer 1 (L1) measurements for the at least one candidate cell; circuitry configured to select a subset of candidate target cells in the list of candidate target cells based on the received information; wherein the circuitry configured to cause the transmission is configured to cause a transmission of an indication of the subset of candidate target cells to the UE.

[0087] The circuit system can be configured to perform optional features associated with the aforementioned device.

[0088] Other specific and preferred aspects are set forth in the appended independent and dependent claims. Features of the dependent claims may be suitably combined with features of the independent claims, and may be combined with combinations other than those expressly listed in the claims.

[0089] When a device feature is described as operable to provide a function, it should be understood that this includes device features that provide the function or are adapted or configured to provide the function. Attached Figure Description

[0090] Some exemplary embodiments will now be described with reference to the accompanying drawings, in which:

[0091] Figure 1 An example embodiment of the network is illustrated schematically;

[0092] Figure 2 An example embodiment of the measurement selection process is illustrated;

[0093] Figure 3 An example embodiment of the signaling diagram for LTM handover is illustrated;

[0094] Figure 4 An example embodiment of the LTM switching timeline is illustrated;

[0095] Figure 5 An example embodiment of the LTM switching timeline is illustrated;

[0096] Figure 6 An example embodiment of the signaling diagram for LTM candidate configurations is illustrated;

[0097] Figure 7 An example embodiment of the signaling diagram for NW RTD indication is illustrated; and

[0098] Figure 8 An example embodiment of the UE and network node is illustrated schematically. Detailed Implementation

[0099] Before discussing the example embodiments in more detail, an overview will first be provided.

[0100] In low-layer (Layer 1 (L1) and / or Layer 2 (L2)) triggered mobility (LTM), the network configures a set of candidate target cells for the UE for LTM handover. The network sends indications of these candidate target cells to the UE. In response, the UE can indicate to the network via an L3 measurement report which candidate target cells the UE has detected.

[0101] Before handover to one or more candidate target cells, the UE can perform L1 measurements on the detected candidate target cells to select the best target cell for handover. Indications of the L1 measurements can be sent to the network in an L1 measurement report, which the network can use to determine which target candidate cell should be used for handover. L1 measurements may include, for example, L1 RSRP measurements.

[0102] Some UEs support L1 measurement, where the received timing difference (RTD) is greater than a predetermined time window, such as the cyclic prefix (CP), but other UEs do not support L1 measurement. RTD is the received timing difference between the DL signal received from the serving cell and the DL signal from the potential LTM target cell. RTD is highly dynamic and can change rapidly (from milliseconds to seconds) depending on UE radio conditions and UE mobility. CP is information repeated at the beginning and end of a symbol, which acts as a guard period to avoid interference between signals arriving via different paths.

[0103] Given that the ability to perform L1 measurements on cells with an RTD greater than CP is optional, some UEs will be able to perform reliable L1 measurements when the RTD is greater than CP, while others will not. For UEs that do not support L1 measurements on cells with an RTD greater than CP, L1 measurements may be impossible, unreliable, or untrustworthy. As a result, a problem arises where the network is unaware that a particular UE has determined that its RTD is greater than CP for one or more candidate cells and that it may be unable to perform L1 measurements on some of these candidate cells. This could lead the network to instruct the UE to perform L1 measurements on candidate cells for which it cannot perform L1 measurements, resulting in unnecessary UE power consumption and potentially unreliable L1 measurements. Furthermore, the network can then select a target cell that is a suboptimal choice for LTM handover.

[0104] In view of the above, in some embodiments, the UE evaluates the RTD of each candidate target cell and determines whether the RTD is greater than, equal to, or less than the CP, and in some cases, determines whether the UE can perform L1 measurements for each cell. The UE sends an indication of this determination to the network, so that the network knows which cells the UE cannot perform L1 measurements for. The network can then avoid instructing the UE to perform L1 measurements on these cells. In this way, embodiments can reduce or avoid unnecessary L1 measurements, thereby improving UE battery life. Furthermore, based on the UE's capabilities and the information received, the network can select cells for LTM handover. For example, the network can select target cells for which reliable L1 measurement information has already been received. In this way, embodiments can reduce the risk of handover to suboptimal target cells.

[0105] In summary, determining whether the RTD is greater than, equal to, or less than the predetermined time window allows devices such as the UE to determine which target cells can perform available L1 measurements. In the context of LTM handover, providing this determination to the network node allows the network node to ultimately select a target cell for LTM handover based on reliable L1 measurements. Power consumption at the UE can also be reduced because the UE's determined knowledge can be used to avoid unnecessary L1 measurements (i.e., L1 measurements for target cells where the RTD > the time window). L1 / L2 triggered or lower-level triggered mobility

[0106] As part of a further NR mobility enhancement work item, 3GPP is specifying mechanisms and procedures for L1 / L2 triggered mobility (LTM) to reduce mobility latency. The main difference between existing mobility and LTM-based mobility is that existing (Layer 3 (L3)) mobility uses L3 measurements and L3 measurement reports (which are based on RRC layer messages). LTM aims to use methods other than RRC signaling for measurement reporting to reduce latency. Furthermore, to reduce handover (HO) latency, the goal is to change the actual cell handover (handover) from L3 commands using RRC signaling to methods other than RRC signaling (i.e., LTM handover commands using, for example, MAC messages).

[0107] LTM is the process by which a User Equipment (UE) changes its serving cell based on L1 / L2 trigger commands. The UE is configured with one or more candidate cells with RRC configuration. In LTM, the network receives L1 measurement reports from the UE, and the network determines and requests a change to the serving cell of (multiple) UEs via cell handover commands (e.g., MAC Control Element (MAC CE)). The MAC CE is used to indicate which LTM candidate cell (e.g., cell ID) will be used as the target for cell handover. Therefore, LTMHO is indicated.

[0108] It can be assumed that L3 measurements will be performed in parallel with any LTM-related measurements. It is assumed that the UE performs intra-frequency measurements and, possibly, inter-frequency measurements as needed.

[0109] Cell handover is triggered by the gNB selecting one of the LTM candidate cell configurations as the target configuration. LTM candidate cell configurations can only be added, modified, and published by the network via RRC signaling.

[0110] LTM supports intra-gNB-DU, intra-gNB-CU, and inter-gNB-DU mobility. LTM also supports inter-frequency mobility, including mobility to inter-frequency cells that are not the current serving cell.

[0111] LTM is currently applicable to UEs in NR connected mode. However, the process may also be applicable to other future states and systems (such as 6G). LTM process

[0112] The current design of the LTM process based on the latest RAN1 and RAN2 protocols can be summarized in the following steps:

[0113] 1. A UE with LTM capability is connected to a cell (serving cell) and is performing L3 measurements on one or more neighboring cells.

[0114] 2. The network provides the UE with an LTM candidate cell configuration, including one or more LTM candidate cells, via RRC messages. - LTM candidate cell configurations can be reference configurations or incremental configurations built upon reference configurations. Each LTM candidate cell configuration can be provided as an incremental configuration built upon a reference configuration, which is used to form the complete candidate cell configuration. Reference configurations can be managed independently, and the UE stores the reference configuration as a separate configuration. When the full candidate cell configuration is applied, it replaces the current UE configuration at the time of cell handover. Although the reconfiguration process performs replacements, it does not necessarily reset the MAC, RLC, or PDCP layers. - In LTM, if the user plane is configured in RRC signaling, the user plane continues without being reset (e.g., LTM within a DU), with the goal of avoiding additional delays in data loss and data recovery.

[0115] 3. The UE performs L1 measurements on one or more candidate cells and reports the results to the network.

[0116] 4. Based on the L1 measurement results reported by the UE, the network can configure the UE to activate one or more Transport Configuration Indication (TCI) states for the MAC CE of one or more candidate cells. A unified TCI state framework is used in LTM. At least two options are available related to target cell TCI control: - The network can activate multiple TCI states for multiple candidate cells before the cell handover command in a separate MAC CE activation command, and the TCI state indication follows in the cell handover command. - Alternatively, both TCI status activation and indication can be performed under a cell handover command (step 5).

[0117] 5. From one or more active LTM candidate cells, the network can select one of the LTM candidate cells as the target cell and use the UE's MAC-CE LTM cell handover command to request the UE to hand over the cell so that the UE can perform an LTM handover to the target cell. - A cell handover command (at least) includes the following: - Index of LTM candidate target configurations applied to LTM cell handover - Indication of the DL and UL (or combined) TCI status ID for the LTM target cell (and possibly activation if not performed before the cell handover in step 4) - DL and UL BWP ID

[0118] 6. The UE is separated from the source cell, and the LTM handover to the target cell is completed.

[0119] Optional / Additional Steps:

[0120] As an additional or optional step, the network may request the UE to prepare for UL synchronization with the potential LTM target cell before the cell handover command. This step can be performed between steps 4 and 5 above.

[0121] In order to prepare one or more LTM candidate cells, the network may initiate a PDCCH command for random access on one or more candidate cells before requesting the actual LTM cell to be handed over to (multiple) target cells.

[0122] On a potential LTM target cell, using the Random Access Channel (RACH), the UE can send a preamble so that the network can obtain the UL timing and timing advance (TA) value of the target cell before the cell handover command.

[0123] However, UL synchronization can also be performed after LTM cell handover, for example, if the early TA acquisition was not performed via PDCCH command before the cell handover command.

[0124] Support for configuring subsequent LTMs between LTM candidate cells. In a subsequent LTM, the UE does not release the configuration of other LTM candidate cells after the LTM is triggered. Therefore, subsequent LTMs can be executed without RRC reconfiguration. Unified TCI State Framework

[0125] 3GPP defined a unified TCI state framework in Rel-17. In Rel-15 / 16, TCI states were configured only for the downlink, while uplink spatial relationships encompassed uplink beam indication. With the unified TCI state concept, TCI states are configured for both downlink and uplink. This configuration is either joint, where the same TCI state covers both UL and DL; or separate, where separate TCIs are configured for DL ​​and UL.

[0126] The unified TCI state framework uses the concept of a common TCI state, where one common TCI / indicator TCI state at a time provides spatial assumptions for the set of signals and channels (PDCCH, PDSCH, PUCCH, PUSCH, CSI-RS, SRS).

[0127] The configuration and control of the unified TCI status are carried out through the following steps: 1. RRC-based configuration with up to 128 TCI states. 2. Based on MAC CE, up to 16 UL or DL ​​TCI states or 8 joint TCI states can be activated and mapped to 8 code points. In LTM, this activation can be performed in a separate MAC CE before the cell handover command or during the cell handover command itself. 3. TCI state pairs based on DCI indicating a single joint TCI state or DL ​​and UL TCI states. In LTM, this indication is made in the cell handover command (which is the MAC CE). L1 and L3 measurements

[0128] In NR, RSRP measurements are performed and reported at Layer 1 (Physical Layer) and Layer 3 (RRC Layer). Measurements can be based on SSB, or if... CSI-MeasConfig It can be configured in the middle or based on CSI-RS.

[0129] L3 measurements are cell-level or beam-level measurements. Beam-level measurements are generated from L1 measurements by applying L3 filtering. Cell-level measurements are derived from L1 measurements using certain rules. L3 RSRP measurements are performed in... MeasResults The RRC measurement report is reported in the information element.

[0130] L1 measurement is a beam-level measurement. L1 RSRP measurement is performed by the UE based on... CSI-ReportConfig Channel State Information (CSI) Reporting. CSI reporting is defined in Section 5.2.1 of TS 38.214. The time and frequency resources that the UE can use to report CSI are controlled by the gNB. CSI may include: Channel Quality Indicator (CQI), Precoding Matrix Indicator (PMI), CSI-RS Resource Indicator (CRI), SS / PBCH Block Resource Indicator (SSBRI), Layer Indicator (LI), Rank Indicator (RI), L1-RSRP, L1-SINR, or CapabilityIndex. Each report setting CSI-ReportConfig [TS 38.331] is associated with a single downlink BWP for channel measurements given in the associated CSI-ResourceConfig and contains parameters(s) for a CSI reporting band. Each CSI resource setting, CSI-ResourceConfig, contains a configuration for a list of S ≥ 1 CSI resource sets, where the list includes references to one or both of the NZP CSI-RS resource sets and the SS / PBCH block sets, or the list includes references to the CSI-IM resource sets. Each CSI resource setting resides in a DL BWP identified by the high-level parameter BWP-id, and all CSI resource settings linked to the CSI reporting setting have the same DLBWP. Reporting configurations for CSI can be aperiodic (using PUSCH), periodic (using PUCCH), or semi-persistent (using PUCCH, and DCI-activated PUSCH).

[0131] For L1-RSRP reporting, if the higher-layer parameter nrofReportedRS in CSI-ReportConfig is configured to 1, the reported L1-RSRP value is defined by a 7-bit value in the range [-140, -44] dBm, with a step size of 1 dB. If the higher-layer parameter nrofReportedRS is configured to a value greater than 1, or if the higher-layer parameter groupBasedBeamReporting is configured to 'enabled', or if the higher-layer parameter groupBasedBeamReporting-r17 is configured, the UE should use differential L1-RSRP reporting, where the maximum measured value of L1-RSRP is quantized as a 7-bit value in the range [-140, -44] dBm, with a step size of 1 dB, and the differential L1-RSRP is quantized as a 4-bit value. The differential L1-RSRP value is calculated in 2 dB steps, referencing the maximum measured L1-RSRP value that is part of the same L1-RSRP reporting instance. The mapping between the reported L1-RSRP values ​​and the measured quantity is described in TS 38.133. LTM measurement

[0132] LTM handover plans are based on L1 measurements. However, the details of these measurements remain open in RAN4 (how to measure, what to measure, when to measure, etc.). In some examples, L3 measurements are included in the L1 measurement report to help make decisions about the LTM target cell.

[0133] Importantly, a UE may not be able to perform L1 measurements on all candidate cells included in the LTM candidate cell configuration. Some UEs will be able to support L1 measurements on candidate target cells whose RTD is greater than, equal to, or less than a predetermined time window (such as a cyclic prefix (CP)), and some UEs will only support measurements on candidate target cells whose RTD is less than or equal to the predetermined time window, as discussed further below. Therefore, the number of cells on which a UE can perform LTM L1 measurements may be less than the maximum number of candidate cells in the LTM candidate cell configuration (which can contain up to 8 cells).

[0134] Given that supporting LTM L1 measurements (e.g., L1-RSRP measurements) for candidate target cells with RTD greater than a predetermined time window (which in many cases can be the cyclic prefix CP) is an optional UE capability, some UEs cannot reliably measure L1-RSRP for candidate cells when the RTD observed on the UE side is greater than the CP.

[0135] This relaxation of RTD conditions can be problematic because the network is unaware of the RTD observed by the UE between its serving cell and neighboring cells. Therefore, the network doesn't know which candidate cells the UE can perform L1 measurements on, can perform reliable L1 measurements, or where the measurement results can be trusted (i.e., candidate cells where RTD ≤ CP). Since the network doesn't know which candidate cells the UE can perform L1 measurements on, it can indicate to the UE the target cells for LTM handover where the UE cannot perform reliable L1 measurements.

[0136] Therefore, a UE with LTM capability may not be able to perform LTM L1 measurements on all configured candidate cells, which may result in unreliable L1 measurements. Unnecessary L1 measurements may deplete the UE's resources and lead to a switch to a suboptimal candidate cell.

[0137] Some embodiments introduce signaling to the network that indicates cells with an RTD higher than, lower than, or equal to a predetermined time window (such as CP). In some embodiments, the problem is addressed by performing downlink selection in a configured cell based on UE capabilities to select candidate cells for which LTM L1 measurements will be performed.

[0138] Figure 1 An embodiment of a network is shown, which includes a user equipment (UE) 10, a current serving cell 20, and a plurality of neighboring cells 22a, 22b, which can serve as candidate target cells for LTM handover. The number of network nodes may differ from that shown.

[0139] exist Figure 1 In the example, the UE can only perform L1 measurements on candidate target cells whose RTD is less than or equal to a predetermined time window (such as CP). The UE does not support performing L1 measurements on candidate target cells whose RTD is greater than the predetermined time window.

[0140] Figure 1 As shown, the UE evaluates the RTD (RTD_1, RTD_2) for each candidate cell 22a, 22b. RTD1 is measured between the signal received by the UE from the serving cell 20 and the signal received by the UE from the neighboring cell 22a. RTD2 is measured between the signal received by the UE from the serving cell 20 and the signal received by the UE from the neighboring cell 22b. In some example embodiments, when the UE is configured with a primary serving cell and one or more secondary cells in a dual-connectivity arrangement, the UE can evaluate the RTD associated with one or more secondary cells. In this case, the RTD is measured between the signal received by the UE from the primary serving cell and the signal received by the UE from one or more secondary cells.

[0141] The UE is configured to transmit an indication to the network that triggers an RTD assessment. This message is called the UE LTM Measurement Indication. The UE LTM Measurement Indication indicates to the network which cells the UE can perform reliable L1 measurements on (i.e., which cells currently meet the criterion RTD ≤ CP). When the UE determines RTD > CP, it may be unable to perform the required measurements, or any L1 measurement results may be invalid, because the UE does not support L1 measurements in this case. If the UE has already performed L1 measurements, this indication can be included in the L1 measurement report to tell the network under which conditions the measurements have been performed. The network can consider this information when making decisions, such as when generating LTM RRC candidate cell configurations or in LTM cell handover decisions.

[0142] Figure 1 Further, an indication of optional transmission from the network to the UE is shown, specifying that the RTD of one or more candidate target cells can be assumed to be less than or equal to the CP. This message is called the network RTD indication and will be discussed in more detail below.

[0143] Figure 2 A timeline of events according to an embodiment is shown. In phase 1001, the network provides the UE with a configuration including a list of eight candidate target cells 22 for LTM handover. In some networks, the maximum number of candidate target cells in the LTM candidate cell configuration is eight. In some examples, the candidate target cell list may include some other number of candidates, such as fewer than eight.

[0144] In phase 1002, the UE detects one or more candidate target cells from candidate target cells 22. In this example, the UE has detected cells 1 through 4. This information can be sent to the network in the L3 measurement report. Note that L3 measurements are performed periodically by the UE.

[0145] In phase 1003, the UE has evaluated the RTD for each of the detected cells and performed a determination regarding whether the RTD is greater than, equal to, or less than a predetermined time window (such as CP). In this example, the UE does not support L1 measurements for cells with RTDs greater than CP. Among the detected cells, only cells 1 and 2 are determined to have RTDs less than or equal to CP. The UE uses UE LTM measurement indication transmission to send an indication of this determination, such as... Figure 1As shown in the diagram. In response to receiving this information, the network can instruct the UE to perform L1 measurements on a subset of detected candidate target cells. This subset may include one or more cells. In this case, the subset includes cell 1 and cell 2. The L1 measurements may be reported to the network node in an L1 measurement report for consideration in its decision-making. In some embodiments, the network updates the candidate target cell list. In some embodiments, the network selects one or more target cells for LTM handover.

[0146] Figure 3 A signaling diagram according to an embodiment is shown, demonstrating how UE LTM measurement indication is implemented.

[0147] Initially, the UE is in RRC connected state.

[0148] In step 1, the UE sends one or more L3 measurement reports, which contain indications of the L3 measurements performed by the UE. L3 measurements and measurement report events can be periodic. L3 measurements are not a prerequisite for RRC configuration, but they are necessary for the UE to send L1 measurement reports.

[0149] In step D1, the network node serving cell (gNB source) prepares a configuration including a list of candidate target cells for LTM handover.

[0150] In step 2, the network node sends the prepared LTM candidate cell configuration to the UE, which contains up to N (e.g., 8) candidate cells, where N indicates the number of configurable LTM cells. In step 3, the UE sends an RRC reconfiguration completion confirmation.

[0151] In step D2, the UE evaluates the RTD of at least one candidate target cell in the candidate target cell list. The candidate target cell list has been received from the network node. In some embodiments, the UE evaluates the RTD for all candidate target cells already detected by the UE. Figure 2 Phase 1002).

[0152] In step D2, the UE may also perform a determination based on its capabilities, RTD, and a predetermined time window (such as the length of the cyclic prefix) to identify which configuration candidate cells it can perform L1 measurements on. The cell is assumed to have been detected and remain detected during the evaluation and / or reporting process. Alternatively, this determination can be made by the network node. In this case, the UE sends the evaluated RTD and UE capabilities to the network node according to steps 4, 6, and / or 8.

[0153] In some embodiments, the UE cannot perform L1 measurements on cells with an RTD greater than CP. In this case, the UE should evaluate the RTD by comparing it with the serving cell of each detected cell in the candidate cell configuration, and select cells with an RTD less than or equal to CP to report to the network.

[0154] The evaluation process can be triggered independently or together with signaling (e.g., DCI or MAC CE), or it can be part of a process such as downlink selection, where evaluations are performed on multiple cells based on L1 / L3 measurement reports.

[0155] In steps 4, 6, and 8, the UE indicates to the network the cells for which it can perform L1 measurements based on the RTD assessment and the UE's capabilities. Specifically, based on the comparison between the RTD assessed in step D2 and the CP, the UE sends an LTM candidate cell indication as an indication of one or more LTM candidate cells for which the UE can perform L1 measurements.

[0156] In some embodiments, the UE's capability is limited to performing L1 measurements on cells with an RTD less than or equal to the CP. Therefore, the LTM candidate cell indication can indicate cells that meet this criterion. In some embodiments, the UE indicates cells that do not meet this criterion. In such cases, the network should avoid instructing the UE to perform L1 measurements on these cells, or avoid selecting these cells for LTM handover.

[0157] Steps 4, 6, and 8 will now be discussed in more detail.

[0158] In step 4, the LTM candidate cell indication is sent as part of the LTM L1 measurement report. This can be an existing L1 measurement report or an LTM-specific measurement report. In step 6, a similar process occurs, except that the LTM candidate cell indication is sent as part of the L3 measurement report.

[0159] LTM candidate cell L1 or L3 measurement reports include: Part One:

[0160] UE LTM measurement indication. This can include the index / measurement ID / cell ID of each candidate cell for which the UE can perform L1 measurements (e.g., cells where RTD ≤ CP). Alternatively, this list can be an exclusion list, where the UE reports cells where RTD >= CP or RTD > CP (i.e., cells for which the UE cannot perform L1 measurements). Another alternative is that the indication can be a flag or bit (e.g., RTD = true / false or 1 / 0 to indicate whether CP ≤ (or >=, >, <) RTD). Part Two:

[0161] If the UE has performed L1 measurements on a subset or all indicated candidate cells, then the L1-RSRP value for the corresponding cell.

[0162] In some embodiments, the UE includes the UE LTM measurement indication in the first part of the measurement report: a. Only in the first L1 / L3 measurement report after LTM candidate cell configuration, i.e., after the UE receives the configuration of at least one candidate target cell including LTM, and / or b. In all L1 / L3 measurement reports, up to the cell handover command, and / or c. If the RTD≤CP condition changes, and / or d. After a certain number of assessments / reports have passed (e.g., by counting the assessments with a counter), and / or e. Based on network requests.

[0163] In the first part of the LTM L1 measurement report, the UE includes a UE LTM measurement indication, which lists all candidate cells for which the UE can perform L1 measurements. The number of indicated cells can be up to the number of cells in the LTM candidate cell configuration. During reporting, the UE can update this part of the report based on UE conditions, as discussed in more detail below.

[0164] In the second part of the report, the UE includes the L1-RSRP value (absolute value or difference, based on SSB or CSI-RS) for each cell that the UE has measured. If the UE is able to measure all cells, this may be all the cells indicated in the first part of the report, or it may be a subset of indicated cells based on downlink selections by some other UE or network.

[0165] In the example embodiment, when the network configures candidate cells #1-8 to the UE, the UE is able to measure and actually also measure and report cells #1-4. The report will include the following parts: Part One ( UE LTM Measurement Indicator ): Candidate Community #1 Candidate Community #2 Candidate Community #3 Candidate Community #4 Part Two (L1-RSRP values ​​of a subset of LTM candidate cells already measured by the UE): L1-RSRP of candidate cell #1 L1-RSRP of candidate cell #2 L1-RSRP of candidate cell #3 L1-RSRP of candidate cell #4

[0166] Figure 4 The illustration shows a sample LTM L1 measurement report that can be used in step 4. More details will follow. Figure 4 .

[0167] In step 8, the LTM candidate cell indication is sent as part of a separate existing or new LTM-based message (e.g., MACCE, DCI, RRC).

[0168] In some embodiments, the UE sends a UE LTM measurement indication to the network in a message separate from any L1 or L3 measurement reports. This indication may include the index / measurement ID / cell ID of each candidate cell for which the UE can perform L1 measurements (e.g., cells with RTD ≤ CP). Alternatively, this list may be an exclusion list, where the UE reports cells with RTD >= CP or RTD > CP (i.e., cells for which the UE cannot perform L1 measurements).

[0169] In some embodiments, the UE may send an indication: a. Once after receiving the candidate cell command, and / or b. If the RTD≤CP condition changes, and / or c. After a certain number of assessments have passed (e.g., by counting the assessments with a counter), and / or d. Based on network requests.

[0170] In some embodiments, the UE should report L1 / L3 measurement results separately based on existing reports.

[0171] When a UE LTM measurement indication is sent in a separate message from the measurement report, the UE should include all candidate cells for which it can perform L1 measurements in the indication portion of that message. The number of indicated cells can be up to the number of cells in the LTM candidate cell configuration. This indication can be included in some existing message (e.g., UE assistance information, MAC CE) or a new LTM-specific message.

[0172] In an example embodiment, when the network configures candidate cells #1-8 to the UE and the UE is able to measure cells #1-4, the indications included in the existing or new messages will be: Candidate Community #1 Candidate Community #2 Candidate Community #3 Candidate Community #4

[0173] Figure 5 An example of such a report that can be used in step 8 is shown below, which will be discussed in more detail below.

[0174] It should be understood that steps 4, 6, and 8 are not mutually exclusive. LTM candidate cell indication can be transmitted using any one of these signals or any combination thereof.

[0175] In some embodiments, based on evaluation and indication, the network and / or UE (dynamically) select LTM candidate cells for which the UE should perform L1 measurements, for example, based on UE capabilities. Although Figure 3 Although not shown, the network can send an indication to the UE of the cells for which the UE should perform L1 measurements. In some embodiments, the network instructs the UE to perform L1 measurements for all cells with an RTD less than or equal to the CP. The L1 measurements can be sent to the network in the L1 measurement report.

[0176] Steps 10, 11, 12, and D3 represent the network behavior upon receiving the indication. In response to the receipt of this indication, the network node considers this information during the cell handover / handover / measurement process. The network selects a target cell based on UE L1 measurements (as well as RTD evaluation results and the determination of the UE's ability to perform L1 measurements on the cell), and in step 13, indicates the cell handover (LTM handover) to the target cell in the LTM cell handover command transmission.

[0177] The following example considers network behavior when RTD > CP, as it introduces the aforementioned problems. However, other cases (such as the opposite case of RTD ≤ CP) can also be used as relevant factors, and decisions can be made accordingly.

[0178] The network can use UE LTM measurement indications in various ways. •LTM candidate configuration

[0179] If an indication (e.g., RTD>CP) is sent in the L3 measurement report, the network may decide not to configure an LTM candidate for the cell under the RTD>CP condition. • LTM cell handover decision

[0180] The network can decide not to perform LTM cell handover for cells where RTD>CP (this can be determined together with or independently of whether the UE supports RTD>CP). For example, in the case where the UE indicates RTD>CP: - If the UE supports RTD>CP, the network can perform cell handover. - If the UE does not support RTD>CP, the network will not perform cell handover for the adjacent cell. - If the UE supports RTD>CP and indicates RTD>CP, the network can still decide not to use the cell for cell handover. • When RTD > CP, LTM downlink selection process

[0181] UE-based downlink selection: - The network can reconfigure the UE and exclude cells where RTD > CP. - Alternatively, the network can instruct the UE in the configuration not to perform downlink selection (downlink selection impact) when RTD>CP.

[0182] Network indicates downlink selection: - The network can exclude cells from the candidate cell list that already meet the following conditions. ○ The UE indicates RTD>CP, and the UE does not support the RTD>CP capability. Update the confirmed

[0183] In some embodiments, because the RTD is dynamic and dependent on network conditions and UE mobility, the UE is configured to perform periodic / semi-persistent or event-triggered RTD assessments and reports. Updating the RTD assessment in this way allows for an updated determination of whether the RTD is greater than, equal to, or less than a predetermined time window (e.g., CP). After being reported to the network, the network can update the candidate target cell list, determine which candidate target cells the UE should perform L1 measurements on, and / or select a target cell for LTM handover based on more up-to-date information. In a periodic / semi-persistent configuration, RTD assessments are performed at specific (configurable or static) time intervals.

[0184] Figure 4 The implementation according to the embodiment is shown. Figure 3 The event timeline is as follows: Step 4, event timeline 100. Initially, in step 102, the network supplies candidate cell configurations to the UE. Then, in steps 104 and 106 respectively, the UE performs RTD evaluation and reports this information to the network in the LTM L1 measurement report. The LTM L1 measurement report consists of a first part and an empty second part. The first part includes a list of candidate cells for which the UE can perform L1 measurements, and the second part is because no measurements have been performed yet. Figure 4 In this context, it is assumed that the UE's capability allows the UE to measure all indicated cells; that is, no further downlink selection is assumed for the measured cells other than downlink selection based on RTD.

[0185] In step 108, the UE re-evaluates the RTD of the candidate cells after a predetermined time or after being instructed to do so. Following the re-evaluation / updated evaluation, an updated LTM L1 measurement report is sent in step 110, wherein the first part includes an updated list of cells that the UE can measure, and the second part includes any L1 measurements.

[0186] Before the UE receives a cell handover command from the network in step 114 indicating which target cell (i.e., candidate cell #6) will be used for handover, L1 measurements and / or RTD reassessment can occur any number of times (e.g., again in step 112). It should be understood that the timeline shown may include additional steps.

[0187] Figure 5 The implementation according to the embodiment is shown. Figure 3 The event timeline is as follows: Initially, in step 202, the network supplies candidate cell configurations to the UE. Then, in steps 204 and 206, the UE performs RTD evaluations and reports this information in a dedicated UE LTM measurement indication transmission. After L1 measurements are performed, in step 208, these measurements are sent to the network in the normal LTM L1 measurement report. Figure 5 In this context, it is assumed that the UE is able to measure all indicated cells; that is, no further downlink selection is assumed for the measured cells other than downlink selection based on RTD.

[0188] In step 210, the UE re-evaluates the RTD of the candidate cell after a predetermined time or after being instructed to do so. Following the re-evaluation / updated evaluation, in step 212, the updated results are sent to the network using another dedicated UE LTM measurement indication transmission. In step 214, an updated L1 measurement report is also sent.

[0189] Before the UE receives a cell handover command from the network in step 216 indicating which target cell (i.e., candidate cell #6) will be used for handover, L1 measurements and / or a reassessment of the RTD are performed and reported as many times as may occur. It should be understood that the timeline shown may include additional steps.

[0190] Figure 6 An example embodiment is shown where the network influences LTM configuration based on UE RTD assessment. Depending on UE mobility, RTD conditions can change, and therefore the UE may need to send RTD assessment information in either the L3 report or the L1 report shown. The network can use this information in different ways. For example, if the UE does not support RTD>CP capability, the network may not configure LTM for cells with RTD>CP.

[0191] In this scenario, the UE may or may not be configured with LTM, but an RTD>CP evaluation needs to be performed on the L3 measurement. For example, this might occur if the UE supports LTM (LTM capability) and the UE supports RTD>CP (RTD>CP capability).

[0192] The UE may need to report whether RTD > CP during the measurement process in the L3 measurement report for each cell or each beam, as shown in step 5. Alternatively, the UE may always need to add information, or only need to add information if the information changes.

[0193] Upon receiving the report, the network can decide whether to configure an LTM candidate if RTD > CP. In step 6, the network sends a new LTM candidate configuration that does not include cells with RTD greater than CP. In some embodiments, the network may still configure these candidate cells, but it will not perform an LTM cell handover until the UE indicates that RTD is less than CP via an L3 measurement report or an L1 measurement report.

[0194] In some embodiments, in LTM candidate cell configuration ( Figure 3 In step 2) or in a separate message, the network may send an additional NW RTD indication to notify the UE of candidate cells, and the UE may assume that the RTD of these candidate cells is within a predetermined time window (such as CP).

[0195] In some embodiments, this indication is related to the co-location information of the candidate target cell relative to the serving cell. The UE is unaware of whether the cells are co-located, therefore the network needs to indicate this to the UE. When such an indication is received from the network, the UE can assume that the RTD of the candidate target cell is less than or equal to the CP. Therefore, when receiving from the network... NW RTD Instructions In this case, the UE can skip the evaluation of the RTD of the indicated cell to avoid performing unnecessary RTD evaluation.

[0196] In some embodiments, the indication is part of the LTM candidate cell configuration, for example, as a 1-bit value associated with each candidate cell, or it may be included in a separate message.

[0197] In some example embodiments, in certain co-location scenarios (e.g., when cells are physically co-located), the network may assume that the RTD observed by the UE side between the serving cell and the corresponding candidate cell will be within the CP. In this case, the network can assist the UE by indicating that the RTD is always lower than the CP. For example, signaling may have already been included in the LTM candidate cell configuration. Alternatively, this can be indicated in a separate message. With this indication, the UE can skip the RTD evaluation of these candidate cells.

[0198] Figure 7A signaling diagram using NW RTD indication according to an embodiment is shown. When a candidate cell co-located with a serving cell and potentially under some other conditions, the network may assume that the RTD between the serving cell and the candidate cell is less than or equal to the CP. In this case, the network sends an NW RTD indication using LTM candidate cell indication in step 1, or in other embodiments, sends an NW RTD indication in a separate message to indicate to the UE that the RTD is less than the CP.

[0199] This indication can be, for example, a 1-bit value of an additional parameter / field in the LTM candidate cell configuration: RTDbelowCP=0 / 1 (0 = RTD above CP or network unknown, 1 = RTD below CP).

[0200] For example: Candidate cell #1, RTDbelowCP=1 Candidate cell #2, RTDbelowCP=0 Candidate cell #3, RTDbelowCP=0 Candidate cell #4, RTDbelowCP=1 Candidate cell #5, RTDbelowCP=0 Candidate cell #6, RTDbelowCP=0 Candidate cell #7, RTDbelowCP=0 Candidate cell #8, RTDbelowCP=0

[0201] The UE can assume that the RTD of the indicated cell is less than or equal to the CP and include it in the UE LTM measurement indication without evaluating the RTD.

[0202] Figure 8 The illustration shows a UE 10, a source or serving network node 20, and a candidate network node 22 according to an embodiment. Network node 20 supports providing radio coverage within cell 30 and may include distributed elements of a gNB communicating with a central unit. Alternatively, network node 20 may include, for example, a base station or a femtonetwork node.

[0203] UE 10 includes a monitoring circuitry 18 for monitoring the power and / or quality of the link between UE 10 and neighboring candidate cells 32 supported by other network nodes 22. UE 10 also includes a data storage 12 for storing candidate cell configuration information received from network node 20, and an RTD evaluation circuitry 14 for estimating the reception timing difference (RTD) between the signal received from serving cell 30 and the signal received from candidate cell 32. The UE also includes a determining circuitry 17 and a generating circuitry 18, wherein the determining circuitry determines the UE's ability to perform L1 measurements based on the RTD and CP, and the generating circuitry is configured to generate an indication of that capability.

[0204] There is also a transmit and receive circuitry system 16 for sending and receiving messages, including information and data, to and from network node 20. The transmitted messages may include L1 / L3 measurement reports generated by monitoring circuitry system 18, indicating the quality and / or power of links to one or more neighboring cells, and may include one or more indications of the UE's ability to perform L1 measurements on candidate cells. This indication may be included within one or more L1 / L3 measurement reports, or may be sent in a separate message.

[0205] The received messages may include information about candidate target cells, which may be received periodically and updated by network nodes in response to signals such as RTD indications sent by the UE.

[0206] Network node 20 includes a data storage 22 and a transmission and reception circuitry 26 for sending and receiving messages with user equipment 10 and, in some cases, with target network nodes.

[0207] The receiving circuitry system 26 receives L1 and L3 measurement reports and an indication of the UE's ability to perform L1 measurements. The network node 20 includes a selection circuitry system 24 for selecting a set of candidate target cells from a list of candidate target cells based on the indication; this set is the set of candidate target cells to which the UE can perform L1 measurements. The network node also includes a message generation circuitry system for generating a message indicating the candidate target cells for transmission to the UE. In response to the selection circuitry system 24 indicating an updated set of candidate cells, the message generation circuitry system 25 can generate an updated message indicating the updated set of candidate target cells and transmit it to the UE using the transmitting and receiving circuitry system 26.

[0208] Those skilled in the art will readily recognize that the steps of the various methods described above can be performed by a programmed computer. Here, some embodiments are also intended to cover program storage devices, such as digital data storage media, which are machine- or computer-readable and encoded with a machine-executable or computer-executable instruction program, said instructions performing some or all of the steps of the methods. The program storage device can be, for example, a magnetic storage medium such as a digital memory, a disk, and magnetic tape, a hard disk drive, or an optically readable digital data storage medium. Embodiments are also intended to cover computers programmed to perform the steps of the methods described above. The non-transient mode used herein is a limitation on the medium itself (i.e., tangible, not signal-based), rather than a limitation on the persistence of data storage (e.g., RAM and ROM).

[0209] As used in this application, the term "circuit system" may refer to one or more or all of the following:

[0210] (a) Hardware circuit implementation only (such as implementation in analog and / or digital circuit systems only) and

[0211] (b) A combination of hardware circuitry and software, such as (if applicable):

[0212] (i) A combination of (multiple) analog and / or digital hardware circuits and software / firmware, and

[0213] (ii) Any part of a hardware processor (including (multiple) digital signal processors), software, and (multiple) memories that work together to enable a device such as a mobile phone or server to perform various functions, and

[0214] (c) (Multiple) hardware circuits and / or (multiple) processors, such as (multiple) microprocessors or a portion thereof, which require software (e.g., firmware) to function, but may be absent when not in use.

[0215] This definition of circuit system applies to all uses of the term in this application, including in any claim. As another example, as used in this application, the term circuit system also covers only the implementation of hardware circuitry or a processor (or processors) or a portion thereof and its accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuit system also covers baseband integrated circuits or processor integrated circuits for mobile devices (such as UEs), or similar integrated circuits in servers, cellular network devices, or other computing or network devices.

[0216] Although exemplary embodiments of the invention have been described with reference to various examples in the preceding paragraphs, it should be understood that modifications may be made to the given examples without departing from the scope of the claimed invention.

[0217] The features described above can be used in combinations other than those explicitly described.

[0218] Although some features have been described with reference to certain characteristics, these functions can be performed by other features, whether or not they are described.

[0219] While features have been described with reference to certain embodiments, these features may also exist in other embodiments, whether or not they are described.

[0220] While the foregoing description makes efforts to draw attention to those features of the invention that are considered particularly important, it should be understood that the applicant claims protection for any patentable features or combinations thereof mentioned above and / or shown in the drawings, whether or not they are specifically emphasized.

[0221] Other aspects and examples can be described in the following numbered paragraphs: 1. A method performed at a device, comprising: Receive configuration from network nodes, which includes a list of candidate target cells for triggering LTM handover at lower layers; For at least one candidate target cell in the candidate target cell list, perform an evaluation of the reception timing difference (RTD) between the signal received from the serving cell and the signal received from at least one candidate target cell; Determination is performed based on RTD and a predetermined time window, wherein the determination is related to the device's ability to perform Layer 1 L1 measurements for at least one candidate target cell; and This triggers the transmission of specific information to network nodes. 2. According to the method in paragraph 1, the predetermined time window includes the length of the cyclic prefix (CP). 3. According to the method in paragraph 1 or paragraph 2, the information is sent in the L1 measurement report transmission. 4. The method according to any of the preceding paragraphs, wherein the information is sent in the Layer 3 (L3) measurement report transmission. 5. According to the method in paragraph 1 or paragraph 2, the transmission of specific information includes one of the following: This causes information to be transmitted only in the first L1 and / or first L3 measurement reports; This causes information to be transmitted in a predetermined number of L1 and / or L3 measurement reports; or This causes information to be transmitted in all L1 and / or L3 measurement reports until the LTM switch is complete. 6. The method according to any of the preceding paragraphs, wherein the information is transmitted in a transmission separate from any Layer 3 or Layer 1 measurement report transmission. 7. The method according to any of the preceding paragraphs, wherein performing the determination based on RTD and a predetermined time window includes: Identify candidate target cells whose RTD is less than or equal to a predetermined time window; and The information regarding the determination includes indications of candidate cells whose RTD is less than or equal to a predetermined time window. 8. The method according to any of the preceding paragraphs, wherein performing the determination based on RTD and a predetermined time window includes: Identify candidate target cells with an RTD greater than a predetermined time window; and The information identified includes indications of candidate cells with an RTD greater than the predetermined time window. 9. The method according to any of the preceding paragraphs includes: transmitting an indication of whether the device supports or does not support L1 measurement based on whether the RTD is greater than, equal to, or less than a predetermined time window. 10. The method according to any of the preceding paragraphs includes: causing the transmission of an indication that the device supports L1 measurement when the RTD is equal to or less than a predetermined time window. 11. The method according to any of the preceding paragraphs also includes: Receive instructions from the network node regarding the following: for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to a predetermined time window; and Based on the received instructions, for at least one candidate target cell whose RTD is assumed to be less than or equal to a predetermined time window, the evaluation of performing the RTD is skipped. 12. According to the method in paragraph 11, at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window is co-located with the serving cell. 13. The method according to any of the preceding paragraphs further includes: performing L1 measurement on a set of candidate target cells whose RTD is less than or equal to a predetermined time window. 14. According to the method in paragraph 12, receive a configuration for performing L1 measurements only for the candidate cell set. 15. The method according to any of the preceding paragraphs further includes updating the evaluation of the RTD, updating the determination, and causing information about the updated determination to be transmitted to the network node. 16. An apparatus comprising: At least one processor; and At least one memory stores instructions that, when executed by at least one processor, cause the device to perform at least the following: Receive configuration from network nodes, which includes a list of candidate target cells for triggering LTM handover at lower layers; For at least one candidate target cell in the candidate target cell list, perform an evaluation of the reception timing difference (RTD) between the signal received from the serving cell and the signal received from at least one candidate target cell; Determination is performed based on RTD and a predetermined time window, wherein the determination is related to the device's ability to perform Layer 1 L1 measurements for at least one candidate target cell; and This triggers the transmission of specific information to network nodes. 17. The method according to any one of paragraphs 1 to 15 or the apparatus according to paragraph 16, wherein the apparatus includes user equipment. 18. A method performed at a device, comprising: This triggers the transmission of configuration to the User Equipment (UE), which includes a list of candidate target cells for triggering mobility (LTM) handover at lower layers. The UE receives information about the determination made by the UE for at least one candidate target cell in the candidate target cell list, wherein Determine the reception timing difference (RTD) and a predetermined time window based on the signal received by the UE from the serving cell and the signal received by the UE from at least one candidate target cell, wherein the determination is related to the UE’s ability to perform Layer 1L1 measurements for at least one candidate cell; Based on the received information, a subset of candidate target cells in the candidate target cell list is selected; This triggers the transmission of indications of a subset of candidate target cells to the UE. 19. According to the method in paragraph 18, the predetermined time window includes the length of the cyclic prefix (CP). 20. According to the method in paragraph 18 or paragraph 19, wherein the subset includes candidate target cells whose RTD is less than or equal to a predetermined time window. 21. The method according to any one of paragraphs 18 to 20 further includes: inducing the transmission of an instruction to the UE regarding the following: for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to a predetermined time window. 22. According to the method in paragraph 21, at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window is co-located with the serving cell. 23. The method according to paragraph 21 or paragraph 22 further includes inducing the transmission of an instruction to the UE to skip the evaluation of the RTD for at least one candidate target cell having an RTD assumed to be less than or equal to a predetermined time window. 24. The method according to any one of paragraphs 18 to 23, wherein the step of selecting a subset of candidate cells includes: reconfiguring the candidate target cell list for LTM handover to exclude candidate target cells with an RTD greater than a predetermined time window; and the step of causing the transmission of an indication of a subset of candidate target cells to the UE includes causing the transmission of an indication of a reconfigured candidate target cell list to the UE. 25. An apparatus comprising: At least one processor; and At least one memory stores instructions that, when executed by at least one processor, cause the device to perform at least the following: This triggers the transmission of configuration to the User Equipment (UE), which includes a list of candidate target cells for triggering mobility (LTM) handover at lower layers. The UE receives information about the determination made by the UE for at least one candidate target cell in the candidate target cell list, wherein Determine the reception timing difference (RTD) and a predetermined time window based on the signal received by the UE from the serving cell and the signal received by the UE from at least one candidate target cell, wherein the determination is related to the UE’s ability to perform Layer 1L1 measurements for at least one candidate cell; Based on the received information, a subset of candidate target cells in the candidate target cell list is selected; This triggers the transmission of indications of a subset of candidate target cells to the UE. 26. The method according to any one of paragraphs 18 to 24 or the apparatus according to paragraph 25, wherein the apparatus includes network nodes. 27. A computer program, when executed by a processor on a device, causes the device to perform at least the following: Receive configuration from network nodes, which includes a list of candidate target cells for triggering LTM handover at lower layers; For at least one candidate target cell in the candidate target cell list, perform an evaluation of the reception timing difference (RTD) between the signal received from the serving cell and the signal received from at least one candidate target cell; Determination is performed based on RTD and a predetermined time window, wherein the determination is related to the device's ability to perform Layer 1 L1 measurements for at least one candidate target cell; and This triggers the transmission of specific information to network nodes. 28. A computer program, when executed by a processor on a device, causes the device to perform at least the following: This triggers the transmission of configuration to the User Equipment (UE), which includes a list of candidate target cells for triggering mobility (LTM) handover at lower layers. The UE receives information about the determination made by the UE for at least one candidate target cell in the candidate target cell list, wherein Determine the reception timing difference (RTD) and a predetermined time window based on the signal received by the UE from the serving cell and the signal received by the UE from at least one candidate target cell, wherein the determination is related to the UE’s ability to perform Layer 1L1 measurements for at least one candidate cell; Based on the received information, a subset of candidate target cells in the candidate target cell list is selected; This triggers the transmission of indications of a subset of candidate target cells to the UE.

[0222] List of abbreviations BWP: Bandwidth section CP: Cyclic prefix CSI-RS: Channel State Information Reference Signal DCI: Downlink Control Information DL: Downlink ICBM: Inter-cell beam management L1 / L2: Layer 1 / Layer 2 LTM: L1 / L2 Triggered Mobility MAC CE: Media Access Control Element NR: New Radio PDCCH: Physical Downlink Control Channel PDSCH: Physical Downlink Shared Channel PUCCH: Physical Uplink Control Channel PUSCH: Physical Uplink Shared Channel RSRP: Reference Signal Received Power RTD: Receive Timing Difference SRS: Detection Reference Signal SSB: Synchronization Signal Block TA: Time advanced TCI: Transmission Configuration Indicator UE: User Equipment UL: Uplink

Claims

1. An apparatus comprising: At least one processor; as well as At least one memory stores instructions that, when executed by the at least one processor, cause the device to perform at least the following: Receive configuration from network nodes, the configuration including a list of candidate target cells for triggering LTM handover at lower layers; For at least one candidate target cell in the candidate target cell list, an evaluation of the reception timing difference (RTD) between the signal received from the serving cell and the signal received from the at least one candidate target cell is performed. The determination is performed based on the RTD and a predetermined time window, wherein the determination is related to the device’s ability to perform Layer 1 L1 measurements for the at least one candidate target cell; as well as This triggers the transmission of the determined information to the network node.

2. The apparatus of claim 1, wherein the predetermined time window includes the length of the cyclic prefix (CP).

3. The apparatus according to claim 1 or 2, wherein the information is caused to be transmitted in the L1 measurement report transmission.

4. The apparatus according to any of the preceding claims, wherein the information is caused to be transmitted in the Layer 3 (L3) measurement report transmission.

5. The apparatus according to any of the preceding claims, wherein the apparatus is configured to perform the determination based on the RTD and the predetermined time window by: Determine candidate target cells whose RTD is less than or equal to the predetermined time window; and The information determined includes an indication of candidate cells whose RTD is less than or equal to the predetermined time window.

6. The apparatus according to any of the preceding claims, wherein the apparatus is configured to perform the determination based on the RTD and the predetermined time window by: Candidate target cells whose RTD is greater than the predetermined time window are identified; and The information determined includes an indication of candidate cells whose RTD is greater than the predetermined time window.

7. The apparatus according to any preceding claim, wherein the apparatus is configured to: The transmission of an indication that the device supports or does not support L1 measurement is caused by whether the RTD is greater than, equal to, or less than the predetermined time window.

8. The apparatus according to any of the preceding claims, wherein the apparatus is configured to: When the RTD is less than or equal to the predetermined time window, the device is prompted to transmit an indication that it supports L1 measurement.

9. The apparatus according to any of the preceding claims, wherein the apparatus is further configured to: Receive from the network node an indication that, for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to the predetermined time window; and Based on the received instruction, for at least one candidate target cell whose RTD is assumed to be less than or equal to the predetermined time window, the evaluation of the RTD is skipped.

10. The apparatus according to any of the preceding claims, wherein the apparatus is further configured to: L1 measurement is performed on the set of candidate target cells for which the RTD is less than or equal to the predetermined time window.

11. An apparatus comprising: At least one processor; as well as At least one memory stores instructions that, when executed by the at least one processor, cause the device to perform at least the following: This triggers the transmission of a configuration to the user equipment (UE), the configuration including a list of candidate target cells for triggering mobility (LTM) handover at lower layers; The UE receives information regarding the determination made by the UE for at least one candidate target cell in the candidate target cell list, wherein... The determination is based on the reception timing difference (RTD) and a predetermined time window between the signal received by the UE from the serving cell and the signal received by the UE from the at least one candidate target cell, wherein the determination is related to the UE’s ability to perform Layer 1 L1 measurements for the at least one candidate cell; Based on the received information, a subset of candidate target cells in the candidate target cell list is selected; This triggers the transmission of an indication of the subset of candidate target cells to the UE.

12. The apparatus of claim 11, wherein the predetermined time window includes the length of the cyclic prefix (CP).

13. The apparatus of claim 11 or 12, wherein the subset includes candidate target cells whose RTD is less than or equal to the predetermined time window.

14. The apparatus according to any one of claims 11 to 13, wherein the apparatus is further configured to: This triggers the transmission of an instruction to the UE that, for at least one candidate target cell in the candidate target cell list, the RTD can be assumed to be less than or equal to the predetermined time window.

15. The apparatus according to any one of claims 11 to 14, wherein the apparatus is further configured to: When the subset of candidate cells is selected, the candidate target cell list for the LTM handover is reconfigured to exclude candidate target cells whose RTD is greater than the predetermined time window; and when an indication of the subset of candidate target cells is transmitted to the UE, an indication of the reconfigured candidate target cell list is transmitted to the UE.

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