Monitoring of the LTM

Abstract

An apparatus is described herein that includes means for receiving, from a network node, information related to at least one condition for triggering a handover report, generating the handover report including a type of handover and at least one condition for triggering the handover report, wherein the at least one condition is a lack of valid timing advance information or a requirement for the apparatus to perform a random access procedure towards the network node, and providing information to the network node regarding availability of the handover report.

Description

Technical Field

[0001] This disclosure relates to new radio (NR) mobility, and more specifically to mobility robustness optimization (MRO) for NR relative to L1 / L2 triggered mobility (LTM). Background Technology

[0002] Any discussion of the background art throughout the specification should not be construed as an admission that the art is well-known or constitutes part of common general knowledge in the art.

[0003] A Layer 1 or Layer 2 (L1 / L2) triggered mobility transfer (LTM) procedure is provided for handover (HO) of a terminal device (e.g., a user equipment UE) from a source cell to a target cell. During the LTM procedure, a network device (e.g., a gNB) receives multiple L1 measurement reports from the UE, and based on these reports, the gNB changes the UE's serving cell via a cell transfer command signaled through the Media Access Control (MAC) element (MAC CE). The cell transfer command indicates an LTM candidate configuration that the gNB has previously prepared and provided to the UE via Radio Resource Control (RRC) signaling. The UE then switches to the target configuration according to the cell transfer command. The LTM procedure can be used to reduce mobility latency.

[0004] When configured by the network, an uplink (UL) timing advance (TA) acquisition procedure can be initiated for one or more cells different from the current serving cell. For example, the network can request the UE to perform early TA acquisition for a candidate cell before cell handover. Early TA acquisition is triggered by a Physical Downlink Control Channel (PDCCH) command message sent to the UE, which in turn triggers the transmission of a RACH preamble to the candidate target cell. The gNB to which the candidate cell belongs calculates the TA value based on the received RACH preamble and sends the TA value to the gNB to which the serving cell belongs. When an LTM cell handover is triggered, the serving cell provides the newly created TA value to the UE in the LTM cell handover command MAC CE. The UE determines whether to access the target cell using a random access (RA) procedure based on whether a valid TA value is provided in the cell handover command. For LTM without RACH, the UE accesses the target cell using a configured grant provided in the LTM candidate cell configuration and selects a configured grant timing associated with the beam indicated in the cell handover command. Summary of the Invention

[0005] This disclosure provides an apparatus for communication and a method for communication.

[0006] According to a first aspect of this disclosure, an apparatus is provided comprising components for: receiving information from a network node relating to at least one condition for triggering a handover report; generating a handover report, the handover report including a type of handover and the at least one condition for triggering the handover report, the at least one condition being either a lack of valid timing advance information or a requirement for the apparatus to perform a random access procedure toward the network node; and providing the network node with an indication of the availability of the handover report.

[0007] On the other hand, this information is included in mobility information elements triggered at a lower layer.

[0008] Alternatively, this information is included in the configuration message.

[0009] According to another aspect, the at least one condition is the lack of effective timing advance information or the requirement for the device to perform a random access procedure toward a network node.

[0010] On the other hand, the type of switching is a switching triggered by a lower layer.

[0011] On the other hand, the switchover report is a successful switchover report.

[0012] On the other hand, the handover report is a wireless link failure report.

[0013] According to another aspect, a method is provided, comprising the steps of: receiving from a network node information relating to at least one condition for triggering a handover report; generating a handover report including a type of handover and at least one condition for triggering the handover report, wherein the at least one condition is a lack of valid timing advance information or a requirement for the device to perform a random access procedure toward the network node; and providing the network node with an indication of the availability of the handover report.

[0014] According to another aspect, the at least one condition is the lack of effective timing advance information or the requirement for the device to perform a random access procedure toward a network node.

[0015] According to another aspect, a computer program is provided, including instructions for causing the device to perform the following steps: receiving information from a network node relating to at least one condition for triggering a handover report; generating a handover report, the handover report including the type of handover and at least one condition for triggering the handover report, wherein the at least one condition is a lack of valid timing advance information or a requirement for the device to perform a random access procedure toward the network node; and providing the network node with an indication of the availability of the handover report. Attached Figure Description

[0016] Exemplary embodiments of this disclosure will now be described by way of example only, with reference to the accompanying drawings, in which:

[0017] Figure 1 A simplified diagram according to an example embodiment is illustrated.

[0018] Figure 2 The diagram illustrates an example of a signaling diagram for the cell handover process.

[0019] Figure 3 An example flowchart according to one embodiment is illustrated.

[0020] Figure 4 A simplified block diagram of a device according to an example embodiment is shown. Detailed Implementation

[0021] In the following description, various exemplary embodiments will be used, for example, as examples of communication networks to which embodiments can be applied, and communication network architectures based on 3GPP standards for communication networks such as 5G / NR, as examples, without limiting the embodiments to this architecture. It will be apparent to those skilled in the art that the embodiments can also be applied to other types of communication networks in which mobile communication principles are integrated with D2D (device-to-device) or V2X (vehicle-to-everything) configurations, such as SL (sidelink), Wi-Fi, Global Microwave Access Interoperability (WiMAX), Bluetooth®, Personal Communication Services (PCS), Wideband Code Division Multiple Access (WCDMA), systems using Ultra Wideband (UWB) technology, Mobile Ad Hoc Networks (MANET), wired access, etc. Furthermore, without loss of generality, the description of some exemplary embodiments relates to mobile communication networks; however, the principles of this disclosure can be extended and applied to any other type of communication network, such as wired communication networks.

[0022] The following examples and embodiments should be understood as illustrative examples only. Although the specification may refer to "a," "an," or "some" (or more) examples or embodiments in several places, this does not necessarily mean that each such reference relates to the same (or more) examples or embodiments, or that a feature applies only to a single example or embodiment. Individual features of different embodiments may also be combined to provide other embodiments. Furthermore, terms such as "comprising" and "including" should be understood not to limit the described embodiments to consisting only of those features already mentioned; these examples and embodiments may also include features, structures, units, modules, etc., not specifically mentioned.

[0023] As used in this application, the term "circuit system" may refer to one or more or all of the following: (a) a circuit implementation that is only hardware (such as an implementation that is only in analog and / or digital circuit systems) and (b) a combination of hardware circuitry and software, such as (where applicable):

[0024] (i) a combination of analog and / or (multiple) digital hardware circuitry with software / firmware, and (ii) any portion of (multiple) hardware processors together with software (including (multiple) digital signal processors), software, and (multiple) memories, which work together to enable a device such as a mobile phone or server to perform various functions.

[0025] (c) (a ...

[0026] The definition of "circuit system" applies to all uses of the term in this application, including in any claim. As a further example, as used in this application, the term "circuit system" also covers only hardware circuitry or a processor (or processors) or a portion of hardware circuitry or a processor and its accompanying software and / or firmware implementation. The term "circuit system" also covers (e.g., and if applicable to a particular claim element) baseband integrated circuits or processor integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or network devices.

[0027] A basic system architecture for a (telecommunications) communication network, including mobile communication systems, can be applied using some examples of embodiments. This architecture may include the architecture of one or more communication networks, comprising (multiple) radio access network subsystems and (multiple) core networks. The architecture may include one or more communication network control elements or functions, access network elements, radio access network elements, access service network gateways, or base transceiver stations, such as base stations (BS), access points (AP), NodeBs (NBs), eNBs or gNBs, distribution units (DUs) or central / centralized units (CUs), which control corresponding coverage areas or (multiple) cells. One or more communication stations (such as communication elements or functions, like user equipment or terminal equipment, such as user equipment UE) or another device with similar functionality (such as modem chipsets, chips, modules, etc., which may also be part of a station, a communication-enabled element or function, or an application, such as a UE, an element or function that can be used in a machine-to-machine communication architecture, or attached as a separate element to such a communication-enabled element, function, or application, etc.) can communicate via one or more channels through one or more communication beams to transmit several types of data in multiple access domains. In addition, core network elements or network functions, such as gateway network elements / functions, mobility management entities, mobile switching centers, servers, databases, etc., may be included.

[0028] The following description provides further details on alternatives, modifications, and variations. gNB includes, for example, nodes that provide NR user plane and control plane protocol termination to the UE and are connected to the 5GC via the NG interface, such as according to Section 3.2 of 3GPP TS 38.300 V16.6.0 (2021-06) incorporated by reference.

[0029] The gNB Central Unit (gNB-CU) includes logical nodes that carry, for example, the RRC, SDAP, and PDCP protocols of the gNB or the RRC and PDCP protocols of the en-gNB, and controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU.

[0030] A gNB distributed unit (gNB-DU) comprises, for example, logical nodes carrying gNBs or en-gNBs at the RLC, MAC, and PHY layers, and its operation is partially controlled by the gNB-CU. One gNB-DU supports one or more cells. A cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0031] The gNB-CU-Control Plane (gNB-CU-CP) includes, for example, logical nodes carrying the control plane portion of the gNB-CU for the en-gNB or gNB, the RRC and PDCP protocols. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU.

[0032] The gNB-CU-User Plane (gNB-CU-UP) includes, for example, the user plane portion of the gNB-CU carrying the PDCP protocol for the en-gNB, and logical nodes carrying the user plane portion of the PDCP protocol for the gNB-CU and the SDAP protocol. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, according to Section 3.1 of 3GPP TS 38.401 V16.6.0 (2021-07) incorporated by reference.

[0033] Different functional divisions between central units and distributed units are possible, for example, as referred to as the following options: Option 1 (Class 1A partitioning): The functional division in this option is similar to the 1A architecture in a DC. The RRC is located in the central unit. PDCP, RLC, MAC, physical layer, and RF are located in the distributed units. Option 2 (Class 3C classification): The functional division in this option is similar to the 3C architecture in a DC (Distributed Control) system. RRC and PDCP are located in the central unit. RLC, MAC, physical layer, and RF are located in the distributed unit. Option 3 (Internal partitioning within RLC): Low RLC (part of the RLC functionality), MAC, physical layer, and RF are located in the distributed unit. PDCP and high RLC (another part of the RLC functionality) are located in the central unit. Option 4 (RLC-MAC partitioning): MAC, physical layer, and RF are located in the distributed unit. PDCP and RLC are located in the central unit. Alternatively, for example, according to Section 11 of 3GPP TR 38.801 V14.0.0 (2017-03) incorporated by reference.

[0034] gNB supports different protocol layers, such as Layer 1 (L1) – the physical layer. NR's Layer 2 (L2) is divided into the following sublayers: Media Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP), among which: The physical layer provides a transmission channel to the MAC sublayer; The MAC sublayer provides logical channels to the RLC sublayer; The RLC sublayer provides RLC channels to the PDCP sublayer; The PDCP sublayer provides radio bearers to the SDAP sublayer; The SDAP sublayer provides QoS flows to 5GC; Comp. refers to header compression, and Segm. refers to segmentation. The control channels include (BCCH, PCCH).

[0035] Layer 3 (L3) includes, for example, Radio Resource Control (RRC), as per Section 6 of 3GPP TS38.300 V16.6.0 (2021-06) incorporated by reference.

[0036] RAN (Radio Access Network) nodes or network nodes (e.g., gNB, base station, gNB CU or gNB DU or portions thereof) may be implemented using means, for example, having at least one processor and / or at least one memory (with computer-readable instructions (computer program)), the means being configured to support and / or provide and / or process CU and / or DU related functions and / or features, and / or at least one protocol (sub) layer of the RAN (Radio Access Network), such as Layer 2 and / or Layer 3.

[0037] The gNB CU and gNB DU portions can, for example, be co-located or physically separated. The gNB DU can even be further split, for example, into two parts, one including processing equipment and the other including antennas. The Central Unit (CU) can also be referred to as BBU / REC / RCC / C-RAN / V-RAN, O-RAN, or a portion thereof. The Distribution Unit (DU) can also be referred to as RRH / RRU / RE / RU, or a portion thereof. In the various exemplary embodiments of this disclosure below, the CU-CP (or more generally, the CU) can also be referred to as a (first) network node supporting at least one of the Layer 3 protocols of the Central Unit Control Plane Functions or the Radio Access Network; and similarly, the DU can be referred to as a (second) network node supporting at least one of the Layer 2 protocols of the Distribution Unit Functions or the Radio Access Network.

[0038] The gNB-DU supports one or more cells and can therefore be used as a serving cell for, for example, a user equipment (UE). The UE may include wireless or mobile devices, devices with a radio interface for interacting with the RAN (Radio Access Network), smartphones, in-vehicle devices, IoT devices, M2M devices, etc. The UE or device may include: at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured, together with the at least one processor, to cause the device to perform at least certain operations, such as an RRC connection to the RAN. The UE is configured, for example, to generate messages (e.g., including a cell ID) that will be transmitted via radio to the RAN (e.g., to reach and communicate with the serving cell). The UE may generate, transmit, and receive RRC messages containing one or more RRC Packet Data Units (PDUs).

[0039] The UE can have different states (e.g., according to sections 42.1 and 4.4 of 3GPP TS 38.331 V16.5.0 (2021-06) which have been incorporated by reference). When an RRC connection has been established, the UE is, for example, in the RRC_CONNECTED state or in the RRC_INACTIVE state.

[0040] In the RRC_CONNECTED state, the UE can: Store the AS context; Transmit unicast data to / from UE; Monitor the control channel associated with the shared data channel to determine whether data is being scheduled for the data channel; Provides channel quality and feedback information; Perform neighboring cell measurements and generate measurement reports.

[0041] The RRC protocol includes, for example, the following main functions: RRC connection control; Measurement configuration and reporting; Establishing / modifying / releasing measurement configurations (e.g., intra-frequency, inter-frequency, and inter-RAT measurements); Establishing and releasing measurement intervals; Measurement report.

[0042] The general functions and interconnections of the elements and functions described (which also depend on the actual network type) are known to those skilled in the art and are described in the relevant specifications, so that detailed descriptions may be omitted for brevity. However, it should be noted that, in addition to those described in detail below, several additional network elements and signaling links may be employed for communication to or from elements, functions, or application endpoints, communication network control elements (such as servers, gateways, radio network controllers), and other elements of the same or other communication networks.

[0043] The communication network architecture considered in the example implementation can also communicate with other networks, such as the public switched telephone network or the Internet. The communication network can also support cloud services for the use of virtual network elements or their functions. It should be noted that the virtual network portion of a telecommunications network can also be provided by non-cloud resources, such as internal networks. It should be understood that network elements and / or corresponding functions of access systems, core networks, etc., can be implemented using any node, host, server, access node, or entity suitable for the purpose. Typically, network functions can be implemented as network elements on dedicated hardware, software instances running on dedicated hardware, or virtualized functions instantiated on a suitable platform (e.g., cloud infrastructure).

[0044] Furthermore, network elements (such as communication elements, like UEs, terminal equipment, control elements or functions, such as access network elements, like base stations / BSs, gNBs, radio network controllers, core network control elements or functions, like gateway elements) or other network elements or functions as described herein, as well as any other elements, functions, or applications, may be implemented by software (e.g., computer program products for computers) and / or by hardware. To perform their respective processing, the corresponding devices, nodes, functions, or network elements may include several parts, modules, units, components, etc. (not shown) required for control, processing, and / or communication / signaling functions. Such components, modules, units, and parts may include, for example, one or more processors or processor units, including one or more processing sections for executing instructions and / or programs and / or processing data; storage or memory units or components (e.g., ROM, RAM, EEPROM, etc.) for storing instructions, programs, and / or data, serving as working areas for processors or processing sections, etc.; input or interface components (e.g., floppy disks, CD-ROMs, EEPROMs, etc.) for inputting data and instructions via software; user interfaces (e.g., screens, keyboards, etc.) for providing users with the possibility of monitoring and manipulation; and other interfaces or components (e.g., wired and wireless interface components, including wireless interface components such as antenna units, components for forming wireless communication sections, etc.) under the control of processor units or sections, wherein the corresponding components forming the interface (e.g., wireless communication section) may also be located at a remote site (e.g., a wireless headend or wireless station, etc.). It should be noted that in this specification, "processing section" should not be considered merely as a physical part of one or more processors, but may also be considered as a logical division of the processing tasks involved, performed by one or more processors. It should be understood that, based on some examples, a so-called "liquid" or flexible network concept can be adopted, in which the operation and function of network elements, network functions, or another entity of the network can be performed in a flexible manner in different entities or functions, such as in nodes, hosts, or servers. In other words, the "division of labor" between the network elements, functions, or entities involved can vary on a case-by-case basis.

[0045] As described above, this disclosure generally relates to a (LTM) procedure provided for handover of a terminal device (e.g., a user equipment UE) from a source cell to a target cell. Although a handover from one cell to another can be successful, interruptions may still occur during the handover, for example, if the T310 timer may start but not terminate before the handover is complete. Successful Handover Report (SHR) was introduced in Rel-17 to optimize the timing aspects of handover.

[0046] The SHR can be configured by both the source and target nodes during handover (different nodes configure different parts of the SHR) (the SHR configuration is within the handover command), and if necessary, the target node retrieves it and forwards it back to the source node using the UEInformationRequest / UEInformationResponse information elements. If the UE has a successful HO report available for reporting, the UE includes the availability of the SHR in each completion message sent during the RRC process (i.e., in the RRCReconfigurationComplete, RRCReestablishmentComplete, RRCSetupComplete, and RRCResumeComplete messages). The UE can discard the SHR after it has been stored for 48 hours, for example, by releasing the UE variable VarSuccHO-Report.

[0047] The SHR currently defined in 3GPP includes: - The source cell ID and target cell ID for the handover. -Location information, - Latest wireless link measurements for all measurement IDs available when performing a handover for all handover types. - As the reason that triggers the generation of SHR, i.e. t310-cause , t312-cause , t304-cause , - Latest wireless measurement results of candidate target cells under conditional HO. - The time elapsed between the execution of the conditional HO towards the target cell and the receipt of the corresponding latest configuration for the selected target cell. -C-RNTI of the target cell -When T304 is above the threshold RA-InformationCommon . - In the case of DAPS HO, the indication that the source cell had failed before being released and the time of the resulting outage are also recorded.

[0048] The UE records the SHR if the SHR configuration is received before the handover is performed and at least one of the following criteria is met: - The UE's T310 timer has exceeded the threshold configured by the source node. - The UE's T312 timer has exceeded the threshold configured by the source node. - The UE's T304 timer has exceeded the threshold configured by the target node.

[0049] Under the current SHR specification, the UE begins checking these criteria simultaneously with HO execution. HO execution is initiated upon receipt of the HO command (with a synchronized RRC connection reconfiguration message), and a report is finally recorded after a successful handover if at least one criterion is met. In LTM, cell change is triggered upon receiving a cell handover command (via MAC CE) and only forwarding continues to the new cell without a RACH procedure (cell handover without RACH). For this reason, LTM is currently excluded from SHR reporting. The presence and performance of LTM-based handovers are currently not reflected in the SHR.

[0050] More specifically, there may be cases where the MAC control element (CE) command does not trigger a cell handover without RACH, because the UE may receive a MAC-CE without a valid TA value or information. This is not currently reflected in the SHR, although information about whether a cell change occurs without a RACH procedure is crucial for LTM.

[0051] In addition, the following situation may occur: Cell change is triggered without RACH due to the UE receiving a MAC-CE including TA value or information. However, the initial uplink transmission may fail, resulting in a certain number of RLC-controlled retransmissions. If the number of these retransmissions remains below a threshold (e.g., the "rlc-MaxNumRetx" threshold), no radio link failure is reported. In this case, the cell change is RACH-less and is considered successful, even though the radio link conditions toward the target cell are not optimal. This situation may currently go undetected.

[0052] In another scenario, the UE can be configured to perform different mobility procedures, including legacy handover and LTM-based handover. It is possible that the network may be unable to distinguish whether the SHR received from the UE is based on legacy handover or LTM-based handover.

[0053] Figure 1 A simplified diagram according to an example embodiment is illustrated. At 102, the UE receives a cell handover command from the network (e.g., gNB). The cell handover command can be considered a handover command. In the specific case of this example, the cell handover command does not contain a valid timing advance (TA) value or any other information related to the TA. UE 100 then triggers the creation of a SHR. In this case, the SHR triggering criterion is the absence of a valid TA, which should ensure that the UE is synchronized with the target cell and the UE must fall back to the RACH-based procedure 106. Once the RACH-based procedure is completed, UE 100 responds to the network using an RRC reconfiguration message.

[0054] Figure 2 The diagram illustrates an example of a signaling diagram for a cell handover process when an SHR including an LTM-with-RACH-cause is generated, serving two separate Transport Points (TRPs), where the source PCell is linked to TRP1 and the target candidate PCell is linked to TRP2. This process is used when a UE moves from the source PCell at TRP1 to the target PCell at TRP2 within the same gNB-DU via LTM during NR operation. In this scenario, the valid TA value for the selected target candidate PCell is not provided in the cell handover command message. This results in a RACH backoff when the UE initiates access to the target PCell via the RACH procedure.

[0055] In step 202, the UE connects to the primary cell (PCell) via an RRC connection. In step 206, the gNB sends an RRC reconfiguration message to the UE. This message includes information related to at least one condition for triggering a handover report, which may follow LTM. Triggering a handover report may differ from the actual generation of a handover report, and triggering can be considered the reason for generating a handover report. In an embodiment, the information related to at least one condition for triggering a handover report may be included in an information element, such as LTM-FailureReporting. This information element may include a flag, such as LTM-with-RACH-r19, to check whether LTM was performed using RACH (flag set to true, T) or not using RACH (flag set to false, F). Furthermore, this information element may include a threshold compared to the number of RLC retransmissions required from the first uplink transmission until successful completion. This threshold may be defined as rlc-Retx_percentage_thres and may be measured as a percentage P. In step 208, the UE sends an RRC reconfiguration complete message to the gNB.

[0056] In step 210, the gNB provides LTM configuration and triggers early TA acquisition. As part of this process, the following actions are performed: The UE sends a MeasurementReport message (L3 measurement results) to the gNB-DU, which contains measurements of neighboring cells. The gNB-DU sends a UL RRC MESSAGE TRANSFER message to the gNB-CU, which transmits the received MeasurementReport message. The gNB-CU determines to initiate LTM configuration. The gNB-CU sends a UE CONTEXTMODIFICATION REQUEST message to the gNB-DU, which contains a target candidate cell ID, the candidate cell's LTM configuration ID, an LTM configuration ID mapping list, and CSI resource configuration. The gNB-CU requests PRACH resources from the gNB-DU. The gNB-CU may request the gNB-DU to provide low-layer configuration for generating a reference configuration. If the gNB-DU accepts the LTM configuration request, it responds with a UECONTEXT MODIFICATION RESPONSE message, which includes the low-level RRC configuration (e.g., TCI status configuration, RACH configuration, and CSI report configuration) generated for the accepted target candidate cell. The gNB-CU sends a UE CONTEXT MODIFICATION REQUEST message to both the source and target gNB-DUs, which includes the collected TCI status configuration, and the gNB-CU may send the CSI report configuration for all accepted target candidate cells. The source gNB-DU responds with a UECONTEXT MODIFICATION RESPONSE message, which includes updated low-level configurations, such as the CSI report configuration for the source cell.

[0057] The gNB-CU sends a DL RRC MESSAGE TRANSFER message to the gNB-DU, which includes the generated RRCReconfiguration message with LTM configuration. The gNB-DU forwards the received RRCReconfiguration message to the UE. The UE responds to the gNB-DU with an RRCReconfigurationComplete message. The gNB-DU forwards the RRCReconfigurationComplete message to the gNB-CU via a UL RRC MESSAGE TRANSFER message. The UE sends the L1 measurement results to the gNB-DU, and the gNB-DU decides to execute LTM.

[0058] In step 212, the gNB sends a cell handover command to the UE without a valid TA value. In one embodiment, the absence of a valid TA value can be equivalent to the absence of an invalid TA value, i.e., no TA value is included in the cell handover command. The cell handover command can be in the MAC layer control element. Without the TA value, or with an invalid TA value, the UE cannot adjust its UL transmission timing. Then, in step 214, a random access procedure is performed, and when the RRC connection is successfully established with the target PCell via the RA procedure in step 214 and the UE sends an RRCSetupComplete message to the gNB in ​​step 216, the UE generates an SHR. In step 218, the gNB-DU forwards the RRCSetupComplete message to the gNB-CU via a UL RRC MESSAGE TRANSFER message. In step 220, the UE generates an SHR. The SHR can be considered or also referred to as a handover report. The SHR can contain an indication of the type of handover performed, which can be, for example, a lower-layer triggered handover. This type of lower-layer triggered handover can be referred to as an LTM type handover. A lower-level triggered handover can be a handover within a gNB-DU, a handover between gNB-DUs within the same gNB-CU-UP, or a handover between gNB-DUs with a change in gNB-CU-UP.

[0059] Furthermore, the SHR may include or indicate a condition upon which the SHR is triggered. This condition could be the aforementioned lack of valid TA information. This condition may additionally or alternatively be a requirement for the UE to perform a RACH toward the gNB. In this case, the flag LTM-with-RACH-r19 is set to true, T. Finally, in step 222, the gNB can obtain the SHR from the UE. This acquisition can be performed as a result of an indication from the UE that the SHR to the gNB has been generated and / or become available.

[0060] Figure 3 An example flowchart according to one embodiment is illustrated. In step 300, the UE receives information from the network node relating to one or more conditions for triggering a handover report. The UE may be referred to as a device, and the network node may be a gNB. This information may be included in a mobility information element triggered at a lower layer. This information element may be named LTM-FailureReporting-r19.

[0061] In step 310, the UE generates a handover report after receiving a cell switching command that does not indicate a valid TA value. The handover report may be an SHR (Signaled Handover Request), and it may contain an indication of the handover type and an indication of one or more conditions that triggered the handover report. These conditions may include the absence of valid TA information or a requirement for the UE to perform a random access procedure toward a network node. The random access procedure may also be toward a network node from which the information related to the conditions for triggering the handover report was received, but from a different network node.

[0062] In step 320, the UE may provide the network node with an indication that a handover report is available. This indication does not imply that the UE actively sends a handover report to the network node. Instead, the network node may obtain the handover report, for example, according to the procedures defined in 3GPP TS 37.340.

[0063] An example of the presence of the aforementioned information element LTM-FailureReporting-r19 can be found in the following 3GPP TS 38.331 specification, which contains multiple information elements. SuccessHO-Config-r19 ::= SEQUENCE { thresholdPercentageT304-r17 ENUMERATED {p40, p60,p80, spare5, spare4, spare3, spare2, spare1} OPTIONAL, --Need R thresholdPercentageT310-r17 ENUMERATED {p40, p60,p80, spare5, spare4, spare3, spare2, spare1} OPTIONAL, --Need R thresholdPercentageT312-r17 ENUMERATED {p20, p40,p60, p80, spare4, spare3, spare2, spare1} OPTIONAL, --Need R LTM-FailureReporting-r19 ::= SEQUENCE { >LTM-with-RACH -r19 ENUMERATED {TRUE,FALSE} OPTIONAL, --Need R >threshold rlc-Retx_percentageENUMERATED {p40, p60,p80, spare5, spare4, spare3, spare2, spare1} OPTIONAL, --Need R ... } ... }

[0064] In addition, the content of an SHR may include the following elements: - The source cell ID and target cell ID for the handover. -Location information, - The latest wireless link measurement of all measurement IDs available when switching is performed for all switch types. - The reasons that trigger the generation of SHR are t310-cause, t312-cause, t304-cause, LTM-with-RACH-cause, and LTM-target-access-cause. - Latest wireless measurement results of candidate target cells under conditional HO. - The time elapsed between the execution of the conditional HO towards the target cell and the receipt of the corresponding latest configuration for the selected target cell. -C-RNTI of the target cell -RA-InformationCommon when T304 is above the threshold. - In the case of DAPS HO, the indication that the source cell failed before being released and the resulting outage time are also recorded. -HO_type ENUMERATED {ltm, spare 1, spare 2}

[0065] Figure 4 A simplified block diagram of a device 400 suitable for implementing some example embodiments of the present disclosure is shown. Device 400 may be provided for implementing a communication device, such as user equipment 100, or as... Figure 2 The network node 200 or 201 is shown. As shown, the device 400 includes one or more processors 420, one or more memories 430 coupled to the processors 420, and one or more communication modules 410 coupled to the processors 420.

[0066] Communication module 410 is used for bidirectional communication. Communication module 410 has at least one antenna to facilitate communication. The communication interface can represent any interface required for communication with other network elements.

[0067] Processor 420 can be any type suitable for a local technology network and can include one or more of the following: general-purpose computer, special-purpose computer, microprocessor, digital signal processor (DSP), and processor based on a multi-core processor architecture, as non-limiting examples. Device 400 can have multiple processors, such as application-specific integrated circuit chips that are time-dependent on the clock of a synchronous main processor.

[0068] Memory 430 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 434, electrically programmable read-only memory (EPROM), flash memory, hard disk, optical disc (CD), digital video disc (DVD), and other magnetic and / or optical storage. Examples of volatile memories include, but are not limited to, random access memory (RAM) 432 and other volatile memories that do not persist during power loss.

[0069] A computer program that can be stored in ROM 434 may include computer-executable instructions that are executed by the associated processor 420. The processor 420 can perform any appropriate actions and processes by loading the program into RAM 432.

[0070] The embodiments of this disclosure can be implemented by means of a program, enabling the device 400 to execute the reference. Figure 2 Any process discussed in this disclosure. Embodiments of this disclosure may also be implemented by hardware or by a combination of software and hardware.

[0071] In some example embodiments, the program may be tangibly contained in a computer-readable medium, which may be included in device 400 (e.g., in memory 430) or in other storage devices accessible by device 400. Device 400 may load the program from the computer-readable medium into RAM 432 for execution. The computer-readable medium may include any type of tangible, non-transitory storage, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc.

[0072] In some example embodiments, an apparatus is provided including 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 information from a network node relating to at least one condition for triggering a handover report; generate the handover report, the handover report including the type of handover and at least one condition for triggering the handover report, wherein the at least one condition is a lack of valid timing advance information or a requirement for the apparatus to perform a random access procedure toward the network node; and provide the network node with information regarding the availability of the handover report.

[0073] List of abbreviations CE control elements CHO condition switching CP control plane CU Central Unit DU distribution unit gNB Next Generation NodeB HO switch KPIs (Key Performance Indicators) LTM L1 / L2 triggered mobility MAC Media Access Control MRO Mobility Robustness Optimization PHY physical layer RA Random Access RACH Random Access Channel RAN (Radio Access Network) RLC Wireless Link Control RLF wireless link failure RRC (Radio Resource Control) SHR Successful Switch Report TA scheduled in advance TCI Transport Configuration Indicator TS Technical Specifications UE User Equipment UP User Plane

Claims

1. An apparatus comprising components for the following operations: Receive information from the network node relating to at least one condition used to trigger a handover report. The handover report is generated, comprising the type of handover and at least one condition for triggering the handover report, wherein the at least one condition is a lack of valid timing advance information or a requirement for the device to perform a random access procedure toward the network node, and Provide the network nodes with an indication of the availability of the handover report.

2. The apparatus of claim 1, wherein the information is included in a mobility information element triggered at a lower layer.

3. The apparatus according to claim 1 or 2, wherein the information is included in a configuration message.

4. The apparatus according to claim 3, wherein the configuration message is a radio resource control configuration message.

5. The apparatus according to any of the preceding claims, wherein the at least one condition is the lack of valid timing advance information or a requirement for the apparatus to perform a random access procedure toward the network node.

6. The apparatus of claim 1, wherein the type of switching is a lower-level triggered switching.

7. The apparatus of claim 1, wherein the switching report is a successful switching report.

8. A method comprising: Receive information from the network node relating to at least one condition used to trigger a handover report; Generate the handover report, which includes the type of handover and at least one condition for triggering the handover report, wherein the at least one condition is the lack of valid timing advance information or a requirement for the device to perform a random access procedure toward the network node; as well as Provide the network nodes with an indication of the availability of the handover report.

9. The method of claim 8, wherein the at least one condition is the lack of valid timing advance information or a requirement for the device to perform a random access procedure toward the network node.

10. A computer program comprising instructions for causing a device to perform the method according to claims 8 to 9.

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