Method and apparatus for mobility management

Abstract

This application provides a mobility management method and apparatus. The method includes: a first network device receiving a first report sent by a terminal device, the first report including LTM connection failure information; the first network device determining the type of LTM connection failure based on the first report, the type of LTM connection failure including one of the following: too late LTM, too early LTM, or LTM to the wrong cell. According to this application, a SON enhancement scheme for LTM scenarios is introduced, incorporating LTM-related failure information reported by the UE, and defining LTM failure scenarios. This allows the network device to identify LTM failure scenarios based on mobility reports related to LTM scenarios, thereby adjusting corresponding parameters and improving LTM robustness.

Description

Mobility management method and device Technical Field

[0001] The embodiments of the present application relate to the field of communication technologies. Background Art

[0002] Mobility scenarios in wireless communication systems include layer-triggered mobility (L1 / L2 triggered mobility, LTM). In LTM, the network device sends LTM candidate cell configuration information to the terminal device, which then performs downlink and / or uplink synchronization with the LTM candidate cell. The terminal device then performs Layer 1 (L1) measurements and sends the L1 measurement results corresponding to the LTM candidate cell to the network device. Based on the L1 measurement results, the network device determines the LTM target cell for the terminal device to change to and sends this information to the terminal device via Layer 2 signaling. In response, the terminal device then performs the LTM cell change process to the LTM target cell.

[0003] Figure 1 is a possible schematic diagram of the LTM process. As shown in Figure 1, the process may include the following steps:

[0004] Step 1: The user equipment (UE) sends a measurement report to the gNB.

[0005] Step 2: The UE receives configuration information of one or more LTM candidate cells sent by the base station;

[0006] Step 3: The UE stores the received configuration information of the LTM candidate cell and sends a response message to the base station;

[0007] Step 4a: The UE performs downlink synchronization with the LTM candidate cell;

[0008] Step 4b (optional): The UE performs uplink synchronization with the corresponding LTM candidate cell according to the configuration information of the base station;

[0009] Step 5: The UE performs L1 measurement and sends the L1 measurement result to the base station;

[0010] Step 6: The UE receives a MAC CE (Media Access Control) control element) sent by the base station to indicate a cell change command. The MAC CE includes indication information of the LTM target cell.

[0011] In step 6, optionally, the MAC CE may include TA (Timing Advance) information of the LTM target cell;

[0012] Step 7 (optional): If the UE does not have a valid TA corresponding to the LTM target cell, the UE performs a random access procedure with the LTM target cell when performing the LTM cell change procedure with the LTM target cell;

[0013] Step 8: The UE completes the LTM cell change procedure with the LTM target cell.

[0014] In the above process, if step 7 is performed, when the UE successfully completes the random access process with the LTM target cell, it can be considered that the UE has successfully completed the LTM cell change process.

[0015] In the above process, if step 7 is not performed, the UE can be considered to have successfully completed the LTM cell change process when it determines that the network equipment to which the LTM target cell belongs has successfully received the first uplink data sent by the UE. For example, when the UE receives a Physical Downlink Control Channel (PDCCH) addressed with the UE's Cell Radio-Network Temporary Identifier (C-RNTI) in the LTM target cell, which is used to schedule new data transmission, the UE believes that the network equipment has successfully received the first uplink data sent by the UE.

[0016] It should be noted that the above introduction to the technical background is merely intended to provide a clear and complete description of the technical solutions of this application and facilitate understanding by those skilled in the art. Simply because these solutions are described in the background technology section of this application, it should not be assumed that the above technical solutions are well known to those skilled in the art.

[0017] Summary of the Invention

[0018] The inventors discovered that if a connection failure occurs during the LTM process, it is necessary to consider optimizing LTM-related configurations for subsequent mobility management. Connection failures include radio link failure (RLF), handover failure (HOF), timer expiration, or other reasons that lead to a connection failure between the terminal device and the current serving cell.

[0019] Currently, self-organizing networks (SONs) have introduced network optimization mechanisms, including mobility robustness optimization (MRO). The existing MRO mechanism records mobility parameters on terminal devices, generates corresponding mobility reports, and reports them to network equipment. Based on the contents of the mobility reports, the network equipment can determine the type of handover failure, such as handover too late, handover too early, or handover to the wrong cell.

[0020] The mobility report may include at least one of the following reports: a failure report, a success mobility report, a random access report (RA report), a connection establishment failure report (CEF report) or other reports. Among them, the failure report includes a radio link failure report (RLF report) or any one or more of other failure reports, and the successful mobility report includes various successful mobility reports, such as a successful handover report, a successful secondary cell addition or change report, or any one or more of other success reports.

[0021] In addition, the mobility report may include connection failure time information, which may be used to indicate the length of time from the last (or most recent) receipt of a handover command (or reconfiguration message) by the terminal device to the detection of a connection failure by the terminal device.

[0022] However, in the existing SON mechanism, there is no LTM-related optimization operation. Therefore, it is necessary to consider the MRO-related scenario definition in the LTM mobility scenario to assist network devices in optimizing the corresponding configuration parameters.

[0023] To address at least one of the above problems or other similar problems, embodiments of the present application provide a method and apparatus for mobility management.

[0024] According to one aspect of an embodiment of the present application, a method for mobility management is provided, wherein the method includes:

[0025] The first network device receives a first report sent by the terminal device, where the first report includes LTM connection failure information;

[0026] The first network device determines a type of LTM connection failure based on the first report, where the type of LTM connection failure includes one of the following: too late LTM, too early LTM, or LTM to a wrong cell.

[0027] According to another aspect of an embodiment of the present application, there is provided a mobility management apparatus, which is configured on a first network device, wherein the apparatus includes:

[0028] a receiving unit configured to receive a first report sent by a terminal device, wherein the first report includes LTM connection failure information;

[0029] A determining unit is configured to determine a type of LTM connection failure according to the first report, where the type of LTM connection failure includes one of the following: too late LTM, too early LTM, or LTM to a wrong cell.

[0030] In some embodiments, the LTM connection failure information includes at least one of the following:

[0031] First information used to indicate that the mobility type related to the connection failure is LTM;

[0032] Second information for indicating a time length corresponding to the connection failure;

[0033] third information for indicating the cell where the connection failure occurs;

[0034] The fourth information is used to indicate the type of the connection failure.

[0035] In some embodiments, the determining unit determines the type of LTM connection failure according to the first report, including:

[0036] If it is confirmed according to the first report that the terminal device has received the configuration information of the LTM candidate cell, and the terminal device detects a connection failure with the cell that sent the configuration information of the LTM candidate cell, and,

[0037] If the second information does not exist in the first report, or the time length indicated by the second information in the first report is greater than or equal to the first time threshold,

[0038] The determining unit determines that the type of the LTM connection failure corresponding to the first report is late LTM.

[0039] In some embodiments, the determining unit determines the type of LTM connection failure according to the first report, including:

[0040] If it is confirmed according to the first report that the terminal device has detected a connection failure with the LTM target cell, and,

[0041] If the time length indicated by the second information in the first report is less than or equal to the second time threshold, and the cell of the first re-establishment attempt of the terminal device or the cell of the first LTM recovery attempt is the cell in which the terminal device receives the LTM cell change message or the cell in which the terminal device receives the LTM initialization message,

[0042] The determining unit determines that the type of the LTM connection failure corresponding to the first report is premature LTM.

[0043] In some embodiments, the determining unit determines the type of LTM connection failure according to the first report, including:

[0044] If it is confirmed according to the first report that the terminal device has detected a connection failure with the LTM target cell, and

[0045] If the time length indicated by the second information in the first report is less than or equal to the third time threshold, and the cell of the first re-establishment attempt of the terminal device or the cell of the first LTM recovery attempt is a cell other than the cell in which the terminal device receives the LTM cell change message or the cell in which the terminal device receives the LTM initialization message and the LTM target cell,

[0046] The determining unit determines that the type of the LTM connection failure corresponding to the first report is LTM to an error cell.

[0047] One of the beneficial effects of the embodiments of the present application is that: according to the embodiments of the present application, a SON enhancement solution in the LTM scenario is introduced, LTM-related failure information reported by the UE is introduced, and the LTM failure scenario is defined, so that the network device can identify the LTM failure scenario based on the mobility report related to the LTM scenario, thereby making corresponding parameter adjustments and improving the LTM robustness.

[0048] With reference to the following description and accompanying drawings, specific embodiments of the present application are disclosed in detail, indicating the manner in which the principles of the present application can be employed. It should be understood that the embodiments of the present application are not limited in scope. Within the spirit and scope of the appended claims, the embodiments of the present application include many variations, modifications and equivalents.

[0049] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0050] It should be emphasized that the term "include / comprising" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The elements and features described in one figure or one embodiment of the present application can be combined with the elements and features shown in one or more other figures or embodiments. In addition, in the accompanying drawings, similar reference numerals represent corresponding parts in several figures and can be used to indicate corresponding parts used in more than one embodiment.

[0052] FIG1 is a schematic diagram of the LTM process;

[0053] FIG2 is a schematic diagram of a method for mobility management according to an embodiment of the first aspect of the present application;

[0054] FIG3 is a schematic diagram of an information interaction process according to a method according to an embodiment of the present application;

[0055] FIG4 is a schematic diagram of a method for mobility management according to an embodiment of the second aspect of the present application;

[0056] FIG5 is a schematic diagram of a mobility management apparatus according to an embodiment of the present application;

[0057] FIG6 is another schematic diagram of the apparatus for mobility management according to an embodiment of the present application;

[0058] FIG7 is a schematic diagram of a communication system according to an embodiment of the present application;

[0059] FIG8 is a schematic diagram of a network device according to an embodiment of the present application;

[0060] FIG9 is a schematic diagram of a terminal device according to an embodiment of the present application. DETAILED DESCRIPTION

[0061] The above and other features of the present application will become apparent through the following description with reference to the accompanying drawings. In the description and the accompanying drawings, specific embodiments of the present application are disclosed in detail, which illustrate some embodiments in which the principles of the present application can be adopted. It should be understood that the present application is not limited to the described embodiments. On the contrary, the present application includes all modifications, variations and equivalents that fall within the scope of the appended claims.

[0062] In the embodiments of the present application, the terms "first", "second", etc. are used to distinguish different elements from the name, but do not indicate the spatial arrangement or temporal order of these elements, and these elements should not be limited by these terms. The term "and / or" includes any one and all combinations of one or more of the associated listed terms. The terms "comprising", "including", "having", etc. refer to the presence of the stated features, elements, components or components, but do not exclude the presence or addition of one or more other features, elements, components or components.

[0063] In the embodiments of this application, the singular forms "a," "the," etc. include plural forms and should be broadly understood to mean "a" or "a type" rather than being limited to "one." Furthermore, the term "said" should be understood to include both singular and plural forms, unless the context clearly indicates otherwise. Furthermore, the term "according to" should be understood to mean "at least in part based on...", and the term "based on" should be understood to mean "at least in part based on...", unless the context clearly indicates otherwise.

[0064] In the embodiments of the present application, a scenario involving network devices and / or terminal devices is taken as an example.

[0065] In the above scenario, the network device may include at least one of a core network device, a third-party application device, an operation administration and maintenance (OAM), and an access network device.

[0066] The core network device may refer to a device in the core network (CN) that provides service support for the terminal device. As some examples, the core network device may be at least one of the following: a mobility and management entity (MME), an access and mobility management function (AMF) entity, a session management function (SMF) entity, a user plane function (UPF) entity, a location management function (LMF) entity, and the like, which are not listed here one by one. Among them, the AMF entity may be responsible for the access management and mobility management of the terminal, the SMF entity may be responsible for session management, such as the establishment of a user session, and the UPF entity may be a functional entity of the user plane, mainly responsible for connecting to the external network. The LMF entity may manage the overall coordination and scheduling of resources required for the location of the terminal device registered with the core network device or accessing the core network device. It should be noted that in the embodiments of the present application, the entity may also be referred to as a network element or a functional entity, such as the AMF entity may also be referred to as an AMF network element or an AMF functional entity, and so on.

[0067] The third-party application device can be an OTT service (over the top server) or other third-party device.

[0068] OAM is a network device that performs operations, management, and maintenance on the network according to the actual needs of the operator's network operations.

[0069] The access network device is an access device that the terminal device uses to access the communication system wirelessly. The access network device can be a base station (BS), an evolved NodeB (eNodeB), a transmission reception point (TRP), a base station (next generation NodeB, gNB) in the fifth generation (5G) mobile communication system, a base station in the sixth generation (6G) mobile communication system, a base station in a future mobile communication system, or an access node in a WiFi system. The access network device can also be a module or unit that completes part of the functions of the base station. For example, it can be at least one of the following modules or units: a centralized unit (CU), a distributed unit (DU), a centralized unit control plane (CU control plane, CU-CP), a centralized unit user plane (CU user plane, CU-CP), an integrated access backhaul (IAB) or other modules or units. The embodiments of the present application do not limit the specific technology and / or specific device form adopted by the access network device. The access network equipment can be deployed on land, including indoors / outdoors, and can be handheld or vehicle-mounted; it can also be deployed on the water, on an airplane, on a balloon or on a satellite; the access network equipment can be deployed in a fixed location or on a mobile carrier, and the embodiments of the present application do not limit this.

[0070] In the above scenarios, a terminal device can be a device with wireless transceiver capabilities that can send signals to and / or receive signals from an access network device. A terminal device can also be referred to as a terminal, mobile station, or mobile terminal. A terminal device can be a mobile phone, tablet, or other device with wireless intelligent transceiver capabilities. Terminal devices can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), the Internet of Things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, and various smart scenarios.

[0071] In the above scenarios, access network devices and terminal devices, and terminal devices and terminal devices can communicate via licensed spectrum, unlicensed spectrum, or both. The embodiments of this application do not limit the spectrum resources used for wireless communications.

[0072] The following describes embodiments of the present application with reference to the accompanying drawings and detailed descriptions. For ease of description, the following description uses a base station as an example of an access network device. In the following description, "if," "under the circumstances," and "when" can be used interchangeably to avoid confusion.

[0073] Embodiments of the first aspect

[0074] An embodiment of the present application provides a method for mobility management, which is described from the perspective of a first network device.

[0075] FIG2 is a schematic diagram of a method for mobility management according to an embodiment of the present application. As shown in FIG2 , the method includes:

[0076] 210: The first network device receives a first report sent by the terminal device, where the first report includes LTM connection failure information;

[0077] 220: The first network device determines the type of LTM connection failure according to the first report. The type of LTM connection failure includes one of the following: too late LTM, too early LTM, or LTM to an incorrect cell.

[0078] It is worth noting that FIG2 above only schematically illustrates an embodiment of the present application, and the present application is not limited thereto. For example, other operations may be added or some operations may be reduced. Those skilled in the art may make appropriate modifications based on the above content, and are not limited to the description of FIG2 above.

[0079] In an embodiment of the present application, the first report is a mobility report, which may include, for example, at least one of the following reports described above: a failure report, a success mobility report, a random access report (RA report), a connection establishment failure report (CEF report) or other reports, etc. For details, please refer to the relevant technology.

[0080] In some embodiments, the LTM connection failure information includes at least one of the following:

[0081] First information used to indicate that the mobility type related to the connection failure is LTM;

[0082] Second information for indicating a time length corresponding to the connection failure;

[0083] third information for indicating the cell where the connection failure occurs;

[0084] The fourth information is used to indicate the type of the connection failure.

[0085] In the above embodiment, the connection failure may include, for example, the aforementioned radio link failure (RLF), handover failure (HOF), timer expiration or other reasons causing the connection failure between the terminal device and the current serving cell, etc. For details, please refer to the relevant technology.

[0086] In the above embodiment, the time length is the length of time from the last (or most recent) receipt of a handover command by the terminal device, or the last (or most recent) receipt of a reconfiguration message, or the last (or most recent) receipt of an LTM cell change message to the detection of the above connection failure by the terminal device. This will be described in detail in the following embodiments.

[0087] FIG3 is a schematic diagram of the information interaction process of the method according to an embodiment of the present application. As shown in FIG3 , the process includes:

[0088] 310: The terminal device receives LTM candidate cell configuration information (LTM cfg) sent by the source base station (SgNB);

[0089] 320: The terminal device determines that a connection failure occurred during the LTM process;

[0090] 330: The terminal device records the LTM connection failure information in the first report;

[0091] 340: The terminal device sends a first report to a receiving node.

[0092] 350: The receiving node sends a first report to the source base station (SgNB) and / or the target base station (TgNB);

[0093] 360: The source base station or the target base station determines the type of LTM connection failure according to the first report.

[0094] In operation 310, the LTM candidate cell configuration information may include cell information of the candidate cell. The candidate cell is configured by the source base station for the terminal device. For details, reference may be made to related technologies.

[0095] In operation 320, the connection failure may occur between the terminal device and the current serving cell or between the terminal device and the LTM target cell. Furthermore, the connection failure may occur at any time after operation 310. The current serving cell is a cell under the source base station, and the LTM target cell may be a cell under the source base station or a cell under the target base station.

[0096] In operation 330, the first report may be an RLF report, but the present application is not limited thereto. As mentioned above, the first report may be any report in the mobility report.

[0097] In operation 330, as described above, the LTM connection failure information may include first information indicating that the mobility type associated with the connection failure is LTM. According to the indication of the first information, the network device may confirm that the mobility type associated with the connection failure is LTM.

[0098] In the above example, the first information can explicitly indicate that the mobility type related to the above connection failure is LTM, or the first information can also be LTM-related information to implicitly indicate that the mobility type related to the above connection failure is LTM. For example, the first information can be the configuration information of the LTM candidate cell or other LTM-related information.

[0099] In operation 330, as described above, the LTM connection failure information may also include second information indicating the time length corresponding to the connection failure. For example, the second information may indicate the time length from the last time the terminal device received a handover command, the last time it received a reconfiguration message, or the last time it received an LTM cell change message (e.g., an LTM cell switch command message) to the time the terminal device detected the connection failure. Based on the time length indicated by the second information, the network device may confirm the type of the connection failure.

[0100] In operation 330, as described above, the LTM connection failure information may further include third information indicating information of a cell where the connection failure occurs. Based on the information of the cell where the connection failure occurs indicated by the third information, the network device may confirm the cell where the connection failure occurs.

[0101] In the above example, the cell information may include at least one of the following information: a cell global identifier (CGI), a physical cell identifier (PCI) and frequency information, a cell identifier (cell ID), a non-public network identifier (NPN ID), a non-terrestrial network identifier (NTN ID), or at least one of other cell identifiers. Among them, the CGI may include a public land mobile network (PLMN ID) and a cell ID. Optionally, the cell information may also include a tracking area code (TAC) and / or identification information of a network device to which the cell belongs, such as a global network device identifier.

[0102] In the above example, the third information may be used in combination with the second information. For example, in operation 330 , the terminal device may include both the second information and the third information in the first report, but the present application is not limited thereto.

[0103] In operation 330, as described above, the LTM connection failure information may further include fourth information indicating the type of the connection failure, such as handover failure or radio link failure. Based on the fourth information, the network device may confirm the type of the connection failure.

[0104] As a possible example, switching failure may occur in steps 6 to 8 shown in Figure 1, and wireless link failure may occur outside steps 6 to 8 shown in Figure 1. For example, before step 6, a wireless link failure occurs between the terminal device and the previous service cell. For another example, after step 8, a wireless link failure occurs between the terminal device and the LTM target cell.

[0105] In each of the above examples, the network device may be the receiving node or the source base station or the target base station shown in FIG. 3 that receives the first report.

[0106] In operation 340, the receiving node is an access network device, which sends a first report request to the terminal device after the terminal device accesses the cell under the access network device, and the terminal device sends the generated first report to the access network device.

[0107] In the example of FIG3 , the access network device is taken as an example that is different from the source base station and the target base station, but the present application is not limited thereto. The access network device may also be the source base station or the target base station shown in FIG3 .

[0108] In operation 350 , after receiving the first report, the access network device may forward the first report to the source base station and / or the target base station (first network device).

[0109] In operation 360 , after receiving the first report, the source base station and / or the target base station (first network device) may determine the type of LTM connection failure according to the first report.

[0110] In some embodiments of operation 360, the source base station and / or the target base station (first network device) determines the type of LTM connection failure based on the first report, including:

[0111] If it is confirmed according to the first report that the terminal device has received the configuration information of the LTM candidate cell, and the terminal device detects a connection failure between the terminal device and the cell that sent the configuration information of the LTM candidate cell (that is, the source service cell of the terminal device), and if the above-mentioned second information (that is, the information used to indicate the time length corresponding to the connection failure) does not exist in the first report, or the time length indicated by the second information in the first report is greater than or equal to the first time threshold, it is determined that the type of LTM connection failure corresponding to the first report is too late LTM.

[0112] In the above embodiment, the first time threshold is used to indicate threshold information of the connection duration between the terminal device and the network device (referred to as the second network device) where the above connection failure occurs. It can be predefined by the protocol or configured by OAM. The first time threshold can be called Tstore_UE_cntxt, for example, but the present application is not limited to this.

[0113] In the above embodiment, the too late LTM may be defined as follows in the protocol:

[0114] Late LTM refers to:

[0115] The terminal device receives first configuration information (for example, configuration information of an LTM candidate cell) sent by a second network device where a connection failure occurs. The first configuration information includes at least one LTM candidate cell information. Before the terminal device successfully receives a first message (for example, an LTM cell switch command message) sent by the second network device to instruct the terminal device to perform an LTM cell change, the terminal device detects that the connection between the terminal device and the second network device has failed, and the terminal device does not report the above-mentioned second information or the above-mentioned second information reported by the terminal device is greater than or equal to the first time threshold.

[0116] It can be understood that the second network device is the network device to which the source service cell of the terminal device belongs.

[0117] In the above embodiment, as described above, the second information is used to indicate the length of time from the last (or most recent) receipt of a handover command (or reconfiguration message, or LTM cell change message) by the terminal device to the detection of a connection failure by the terminal device, and may also be referred to as connection failure time information. The LTM cell change message is, for example, an LTM cell switch command message.

[0118] In the above embodiment, the relevant content about the LTM connection failure information has been described above, and its content is incorporated here.

[0119] In the above embodiment, too late LTM may also be referred to as too late handover, or too late LTM cell switch, and so on.

[0120] In the above embodiment, the following changes may be made to the following descriptions in the protocol:

[0121] In the above embodiment, the following changes may be made to the following descriptions in the protocol:

[0122] In some other embodiments of operation 360, the source base station and / or the target base station (first network device) determines the type of LTM connection failure according to the first report, including:

[0123] If it is confirmed according to the first report that the terminal device has detected a connection failure with the LTM target cell, and if the time length indicated by the above-mentioned second information in the first report is less than or equal to the second time threshold, and the cell of the first re-establishment attempt of the terminal device or the first LTM recovery attempt is the cell in which the terminal device receives the LTM cell change message (for example, LTM cell switch command message) or the cell in which the terminal device receives the LTM initialization message, it is determined that the type of LTM connection failure corresponding to the above-mentioned first report is too early LTM.

[0124] In the above embodiment, the second time threshold is used to indicate threshold information of the connection duration between the terminal device and the network device (referred to as the second network device) where the above connection failure occurs, which can be predefined by the protocol or configured by OAM. The second threshold and the first threshold can be the same, and the second time threshold can be called Tstore_UE_cntxt, for example. The second threshold and the first threshold can also be different, and the present application is not limited to this.

[0125] In the above embodiment, the premature LTM may be defined as follows in the protocol:

[0126] Premature LTM refers to:

[0127] Before the connection fails, the terminal device performs an LTM cell change or LTM initialization, and the second information reported by the terminal device is less than or equal to the second time threshold, and the cell of the first re-establishment attempt or the cell of the first LTM recovery attempt is the cell in which the terminal device receives the LTM cell change message or the cell in which the terminal device receives the LTM initialization message.

[0128] It can be understood that the second network device is the network device to which the source service cell of the terminal device belongs.

[0129] In the above embodiment, the relevant content of the LTM connection failure information and the relevant content of the second information have been described above, and their contents are incorporated here.

[0130] In the above embodiment, too early LTM may also be referred to as too early handover, or too early LTM cell switch, and so on.

[0131] In the above embodiment, the following changes may be made to the following descriptions in the protocol:

[0132] In some further embodiments of operation 360, the source base station and / or the target base station (first network device) determines the type of LTM connection failure according to the first report, including:

[0133] If it is confirmed according to the first report that the terminal device has detected a connection failure with the LTM target cell, and if the time length indicated by the second information in the first report is less than or equal to the third time threshold, and the cell of the first re-establishment attempt of the terminal device or the first LTM recovery attempt is a cell other than the cell in which the terminal device receives the LTM cell change message (such as the LTM cell switch command message) or the cell in which the terminal device receives the LTM initialization message and the LTM target cell, it is determined that the type of LTM connection failure corresponding to the first report is LTM to wrong cell.

[0134] In the above embodiment, the third time threshold is used to indicate threshold information of the connection duration between the terminal device and the network device (referred to as the second network device) where the above connection failure occurs. The third time threshold can be predefined by the protocol or configured by OAM. The third time threshold and the first time threshold can be the same. For example, the third time threshold can be called Tstore_UE_cntxt. The third time threshold and the first time threshold or the second time threshold can also be different. The present application is not limited to this.

[0135] In the above embodiment, LTM to the error cell may be defined as follows in the protocol:

[0136] LTM to the wrong cell means:

[0137] Before the connection fails, the terminal device performs an LTM cell change (e.g., LTM cell switch) or LTM initialization, and the second information reported by the terminal device is less than or equal to the third time threshold, and the cell of the first re-establishment attempt of the terminal device or the first LTM recovery attempt is neither the cell in which the terminal device receives the LTM cell change message (LTM cell switch command message) or the cell in which the terminal device receives the LTM initialization message (i.e., the source cell), nor the cell in which the terminal device detects a failure or the LTM target cell.

[0138] It can be understood that the second network device is the network device to which the source service cell of the terminal device belongs.

[0139] In the above embodiment, the relevant content of the LTM connection failure information and the relevant content of the second information have been described above, and their contents are incorporated here.

[0140] In the above embodiment, LTM to wrong cell may also be referred to as handover to wrong cell, or LTM cell switch to wrong cell, and so on.

[0141] In the above embodiment, the following changes may be made to the following descriptions in the protocol:

[0142] The above embodiments are merely exemplary descriptions of the methods of the present application, but the present application is not limited thereto, and appropriate modifications may be made based on the above embodiments. For example, the above embodiments may be used individually, or one or more of the above embodiments may be combined.

[0143] According to the method of the embodiment of the present application, a SON enhancement solution for the LTM scenario is introduced, LTM-related failure information reported by the UE is introduced, and the LTM failure scenario is defined, so that the network device can identify the LTM failure scenario based on the mobility report related to the LTM scenario, thereby making corresponding parameter adjustments and improving the LTM robustness.

[0144] Embodiments of the second aspect

[0145] The embodiment of the present application provides a method for mobility management, which is described from the perspective of a terminal device. The same contents as those in the embodiment of the first aspect will not be repeated.

[0146] FIG4 is a schematic diagram of a method for mobility management according to an embodiment of the present application. As shown in FIG4 , the method includes:

[0147] 410: The terminal device receives configuration information of the LTM candidate cell;

[0148] 420: When a connection failure occurs, the terminal device records LTM connection failure information in the first report;

[0149] 430: The terminal device sends the first report to the first network device, where the first report is used by the first network device to determine the type of LTM connection failure, where the type of LTM connection failure includes one of the following: too late LTM, too early LTM, or LTM to an incorrect cell.

[0150] It is worth noting that FIG4 above only schematically illustrates an embodiment of the present application, and the present application is not limited thereto. For example, the execution order of the various operations may be appropriately adjusted, and other operations may be added or some operations may be reduced. Those skilled in the art may make appropriate modifications based on the above content, and are not limited to the description of FIG4 above.

[0151] In this embodiment of the present application, the LTM connection failure information includes at least one of the following:

[0152] First information used to indicate that the mobility type related to the connection failure is LTM;

[0153] Second information for indicating a time length corresponding to the connection failure;

[0154] third information for indicating the cell where the connection failure occurs;

[0155] The fourth information is used to indicate the type of the connection failure.

[0156] The relevant contents of the above-mentioned first to fourth information have been explained in the embodiment of the first aspect, and their contents are incorporated here and will not be repeated here.

[0157] According to the method of the embodiment of the present application, a SON enhancement solution for the LTM scenario is introduced, LTM-related failure information reported by the UE is introduced, and the LTM failure scenario is defined, so that the network device can identify the LTM failure scenario based on the mobility report related to the LTM scenario, thereby making corresponding parameter adjustments and improving the LTM robustness.

[0158] Embodiments of the third aspect

[0159] An embodiment of the present application provides a device for mobility management.

[0160] Figure 5 is a schematic diagram of a mobility management apparatus according to an embodiment of the present application. The apparatus may be, for example, a network device, or one or more components or assemblies configured on the network device. Because the principles underlying the problem solved by this apparatus are the same as those of the method of the embodiment of the first aspect, its specific implementation may refer to the implementation of the method of the embodiment of the first aspect, and the details of the commonality will not be repeated.

[0161] As shown in FIG5 , the apparatus 500 includes:

[0162] A receiving unit 510 receives a first report sent by a terminal device, where the first report includes LTM connection failure information;

[0163] The determining unit 520 determines a type of LTM connection failure according to the first report, where the type of LTM connection failure includes one of the following: too late LTM, too early LTM, or LTM to an incorrect cell.

[0164] In some embodiments, the LTM connection failure information includes at least one of the following:

[0165] First information used to indicate that the mobility type related to the connection failure is LTM;

[0166] Second information for indicating a time length corresponding to the connection failure;

[0167] third information for indicating the cell where the connection failure occurs;

[0168] The fourth information is used to indicate the type of the connection failure.

[0169] In the above embodiment, the time length may be the time length from the last time the terminal device receives a handover command, the last time it receives a reconfiguration message, or the last time it receives an LTM cell change message to the time the terminal device detects a connection failure.

[0170] In some embodiments, the determining unit 520 determines the type of the LTM connection failure according to the first report, including:

[0171] If it is confirmed according to the first report that the terminal device has received the configuration information of the LTM candidate cell, and the terminal device detects a connection failure between the terminal device and the cell that sent the configuration information of the LTM candidate cell, and if the above-mentioned second information does not exist in the first report, or the time length indicated by the above-mentioned second information in the first report is greater than or equal to the first time threshold, the determination unit 520 determines that the type of LTM connection failure corresponding to the first report is late LTM.

[0172] In the above embodiment, the first time threshold is used to indicate threshold information of the connection duration between the terminal device and the second network device where the connection failure occurs; the first time threshold is predefined or configured by operation, maintenance and management.

[0173] In the above embodiment, too late LTM refers to:

[0174] The terminal device receives the first configuration information sent by the second network device where the connection fails. The first configuration information includes at least one LTM candidate cell information. Before the terminal device successfully receives the first message sent by the second network device, the terminal device detects that the connection between the terminal device and the second network device has failed, and the terminal device does not report the above-mentioned second information or the above-mentioned second information reported by the terminal device is greater than or equal to the first time threshold. The first message is used to instruct the terminal device to perform an LTM cell change.

[0175] In some other embodiments, the determining unit 520 determines the type of the LTM connection failure according to the first report, including:

[0176] If it is confirmed according to the first report that the terminal device has detected a connection failure with the LTM target cell, and if the time length indicated by the above-mentioned second information in the first report is less than or equal to the second time threshold, and the cell of the first re-establishment attempt of the terminal device or the cell of the first LTM recovery attempt is the cell in which the terminal device receives the LTM cell change message or the cell in which the terminal device receives the LTM initialization message, the determination unit 520 determines that the type of LTM connection failure corresponding to the first report is premature LTM.

[0177] In the above embodiment, the second time threshold is used to indicate threshold information of the connection duration between the terminal device and the second network device where the connection failure occurs; the second time threshold is predefined or configured by operation and maintenance management.

[0178] In the above example, premature LTM refers to:

[0179] Before the connection fails, the terminal device performs an LTM cell change or LTM initialization, and the above-mentioned second information reported by the terminal device is less than or equal to the second time threshold, and the cell of the first re-establishment attempt or the cell of the first LTM recovery attempt is the cell in which the terminal device receives the LTM cell change message or the cell in which the terminal device receives the LTM initialization message.

[0180] In some further embodiments, the determining unit 520 determines the type of the LTM connection failure according to the first report, including:

[0181] If it is confirmed according to the first report that the terminal device has detected a connection failure with the LTM target cell, and if the time length indicated by the above-mentioned second information in the first report is less than or equal to the third time threshold, and the cell of the first re-establishment attempt of the terminal device or the first LTM recovery attempt is a cell other than the cell in which the terminal device receives the LTM cell change message or the cell in which the terminal device receives the LTM initialization message and the LTM target cell, the determination unit 520 determines that the type of LTM connection failure corresponding to the first report is LTM to an error cell.

[0182] In the above embodiment, the third time threshold is used to indicate threshold information of the connection duration between the terminal device and the second network device where the connection failure occurs; the third time threshold is predefined or configured by operation and maintenance management.

[0183] In the above embodiment, LTM to an error cell refers to:

[0184] Before the connection fails, the terminal device performs an LTM cell change or LTM initialization, and the above-mentioned second information reported by the terminal device is less than or equal to the third time threshold, and the cell of the first re-establishment attempt of the terminal device or the first LTM recovery attempt is neither the cell in which the terminal device receives the LTM cell change message or the cell in which the terminal device receives the LTM initialization message, nor the cell in which the terminal device detects a failure or the LTM target cell.

[0185] Figure 6 is another schematic diagram of a mobility management apparatus according to an embodiment of the present application. The apparatus may be a terminal device, or may be one or more components or assemblies configured on the terminal device. Because the principles for solving the problem employed by this apparatus are the same as those of the method of the embodiment of the second aspect, its specific implementation may refer to the implementation of the method of the embodiment of the second aspect, and the details of the commonality will not be repeated.

[0186] As shown in FIG6 , the apparatus 600 includes:

[0187] a receiving unit 610 configured to receive configuration information of an LTM candidate cell;

[0188] a generating unit 620, which records LTM connection failure information into a first report when a connection failure occurs;

[0189] The sending unit 630 sends the first report to the first network device, where the first report is used by the first network device to determine the type of LTM connection failure, where the type of LTM connection failure includes one of the following: too late LTM, too early LTM, or LTM to an incorrect cell.

[0190] In some embodiments, the LTM connection failure information includes at least one of the following:

[0191] First information used to indicate that the mobility type related to the connection failure is LTM;

[0192] Second information for indicating a time length corresponding to the connection failure;

[0193] third information for indicating the cell where the connection failure occurs;

[0194] The fourth information is used to indicate the type of the connection failure.

[0195] In the above embodiment, the time length may be the time length from the last time the terminal device receives a handover command, the last time it receives a reconfiguration message, or the last time it receives an LTM cell change message to the time the terminal device detects a connection failure.

[0196] The above embodiments of the present application are illustrative, but the present application is not limited thereto, and appropriate modifications can be made based on the above embodiments. For example, the above embodiments can be used alone, or one or more of the above embodiments can be combined.

[0197] It is worth noting that the above description only describes the components or modules related to this application, but this application is not limited thereto. The above-mentioned device may also include other components or modules. For the specific content of these components or modules, please refer to the relevant art. In addition, the above-mentioned components or modules can be implemented by hardware facilities such as processors, memories, transmitters, and receivers; the implementation of this application is not limited to this.

[0198] According to the device of the embodiment of the present application, a SON enhancement solution in the LTM scenario is introduced, LTM-related failure information reported by the UE is introduced, and the LTM failure scenario is defined, so that the network device can identify the LTM failure scenario based on the mobility report related to the LTM scenario, thereby making corresponding parameter adjustments and improving the LTM robustness.

[0199] Embodiments of the fourth aspect

[0200] An embodiment of the present application also provides a communication system, including a network device and a terminal device.

[0201] FIG7 is a schematic diagram of a communication system according to an embodiment of the present application, schematically illustrating a situation using a terminal device and a network device as an example. As shown in FIG7 , a communication system 700 may include a network device 710 and terminal devices 720 and 730. For simplicity, FIG7 illustrates only two terminal devices and one network device as an example, but the embodiments of the present application are not limited thereto.

[0202] In the embodiment of the present application, existing services or future services can be transmitted between the network device 710 and the terminal devices 720 and 730. For example, these services may include, but are not limited to, enhanced mobile broadband (eMBB), massive machine type communication (mMTC), and ultra-reliable and low-latency communication (URLLC), etc.

[0203] It is worth noting that FIG7 shows that both terminal devices 720 and 730 are within the coverage range of network device 710, but the present application is not limited thereto. Both terminal devices 720 and 730 may not be within the coverage range of network device 710, or one terminal device 720 may be within the coverage range of network device 710 while the other terminal device 730 is outside the coverage range of network device 710.

[0204] In some embodiments, the network device includes the apparatus 500 described in the embodiment of the third aspect, and is configured to execute the method described in the embodiment of the first aspect. Since the method has been described in detail in the embodiment of the first aspect, its content is incorporated herein and will not be repeated.

[0205] The above-mentioned network device can be an intra-DU mobility scenario, including a gNB-DU and a gNB-CU, or a gNB in ​​an inter-DU mobility scenario, including a source gNB-DU, a candidate or target gNB-DU, and a gNB-CU, and performs the method described in the embodiment of the first aspect.

[0206] In some embodiments, the terminal device includes the apparatus 600 described in the embodiment of the third aspect, and is configured to perform the method described in the embodiment of the second aspect. Since the method has been described in detail in the embodiment of the second aspect, its content is incorporated herein and will not be repeated.

[0207] The above-mentioned terminal device can be a UE in an intra-DU mobility scenario or an inter-DU mobility scenario, and executes the method described in the embodiment of the second aspect.

[0208] An embodiment of the present application also provides a network device, which may be, for example, a base station, such as a gNB in ​​an intra-DU mobility scenario or an inter-DU mobility scenario, but the present application is not limited thereto and may also be other network devices.

[0209] Figure 8 is a schematic diagram illustrating the structure of a network device according to an embodiment of the present application. As shown in Figure 8 , network device 800 may include a processor 810 and a memory 820 ; the memory 820 is coupled to the processor 810 . The memory 820 may store various data and information processing programs, which are executed under the control of the processor 810 .

[0210] In some embodiments, the functions of the device 500 of the embodiment of the third aspect can be integrated into the processor 810, wherein the processor 810 can be configured to execute a program to implement the method described in the embodiment of the first aspect, the content of which is incorporated herein and will not be repeated here.

[0211] In other embodiments, the apparatus 500 of the embodiment of the third aspect may be configured separately from the processor 810. For example, the apparatus 500 of the embodiment of the third aspect may be configured as a chip connected to the processor 810, and the functions of the apparatus 500 of the embodiment of the third aspect may be implemented through the control of the processor 810.

[0212] Furthermore, as shown in FIG8 , network device 800 may further include transceivers 830 and 840. The functions of these components are similar to those in the prior art and are not described in detail here. It is worth noting that network device 800 does not necessarily include all of the components shown in FIG8 ; furthermore, network device 800 may also include components not shown in FIG8 , for which reference may be made to the prior art.

[0213] An embodiment of the present application also provides a terminal device, which may be, for example, a UE, such as a UE in an intra-DU mobility scenario or an inter-DU mobility scenario, but the present application is not limited thereto and may also be other terminal devices.

[0214] Figure 9 is a schematic diagram of a terminal device according to an embodiment of the present application. As shown in Figure 9 , terminal device 900 may include a processor 910 and a memory 920. Memory 920 stores data and programs and is coupled to processor 910. It should be noted that this diagram is exemplary; other types of structures may be used to supplement or replace this structure to implement telecommunication or other functions.

[0215] In some embodiments, the functions of the device 600 of the embodiment of the third aspect can be integrated into the processor 910, wherein the processor 910 can be configured to execute a program to implement the method described in the embodiment of the second aspect, the content of which is incorporated herein and will not be repeated here.

[0216] In other embodiments, the device 600 of the embodiment of the third aspect can be configured separately from the processor 910. For example, the device 600 of the embodiment of the third aspect can be configured as a chip connected to the processor 910, and the functions of the device 600 of the embodiment of the third aspect can be realized through the control of the processor 910.

[0217] As shown in Figure 9 , the terminal device 900 may further include: a communication module 930, an input unit 940, a display 950, and a power supply 960. The functions of these components are similar to those in the prior art and are not described in detail here. It is worth noting that the terminal device 900 does not necessarily include all of the components shown in Figure 9 , and the above components are not essential. Furthermore, the terminal device 900 may also include components not shown in Figure 9 , for which reference may be made to the relevant art.

[0218] An embodiment of the present application further provides a computer program, wherein when the program is executed in a network device, the program causes the network device to execute the method described in the embodiment of the first aspect.

[0219] An embodiment of the present application further provides a storage medium storing a computer program, wherein the computer program enables a network device to execute the method described in the embodiment of the first aspect.

[0220] An embodiment of the present application further provides a computer program, wherein when the program is executed in a terminal device, the program causes the terminal device to execute the method described in the embodiment of the second aspect.

[0221] An embodiment of the present application further provides a storage medium storing a computer program, wherein the computer program enables a terminal device to execute the method described in the embodiment of the second aspect.

[0222] The above devices and methods of the present application can be implemented by hardware or by a combination of hardware and software. The present application relates to such a computer-readable program that, when executed by a logic component, enables the logic component to implement the devices or components described above, or enables the logic component to implement the various methods or steps described above. The present application also relates to a storage medium for storing the above program, such as a hard disk, a magnetic disk, an optical disk, a DVD, a flash memory, etc.

[0223] The method / device described in conjunction with the embodiments of the present application can be directly embodied as hardware, a software module executed by a processor, or a combination of the two. For example, one or more of the functional block diagrams shown in the figure and / or one or more combinations of functional block diagrams can correspond to various software modules of the computer program flow or to various hardware modules. These software modules can respectively correspond to the various steps shown in the figure. These hardware modules can be implemented by solidifying these software modules, for example, using a field programmable gate array (FPGA).

[0224] The software module may be located in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. A storage medium may be coupled to a processor so that the processor can read information from and write information to the storage medium; or the storage medium may be an integral part of the processor. The processor and storage medium may be located in an ASIC. The software module may be stored in the memory of a mobile terminal or in a memory card that can be inserted into the mobile terminal. For example, if a device (such as a mobile terminal) uses a large-capacity MEGA-SIM card or a large-capacity flash memory device, the software module may be stored in the MEGA-SIM card or the large-capacity flash memory device.

[0225] One or more of the functional blocks and / or one or more combinations of functional blocks described in the accompanying drawings may be implemented as a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or any appropriate combination thereof for performing the functions described in this application. One or more of the functional blocks and / or one or more combinations of functional blocks described in the accompanying drawings may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in communication with a DSP, or any other such configuration.

[0226] The present application has been described above in conjunction with specific embodiments. However, those skilled in the art should understand that these descriptions are merely illustrative and are not intended to limit the scope of protection of the present application. Those skilled in the art may make various modifications and variations to the present application based on the spirit and principles of the present application, and such modifications and variations are also within the scope of the present application.

Claims

1. An apparatus for mobility management, configured in a first network device, wherein, The device includes: a receiving unit that receives a first report sent by a terminal device, where the first report includes LTM connection failure information; a determining unit that determines the type of LTM connection failure according to the first report, and the type of LTM connection failure includes one of the following: late LTM, early LTM, or LTM to the wrong cell.

2. The apparatus according to claim 1, wherein, The LTM connection failure information includes at least one of the following: first information for indicating that the mobility type related to the connection failure is LTM; second information for indicating the time length corresponding to the connection failure; third information for indicating the cell where the connection failure occurs; fourth information for indicating the type of the connection failure.

3. The apparatus according to claim 2, wherein, The time length is the time length from the last time the terminal device received a handover command or the last time it received a reconfiguration message or the last time it received an LTM cell change message to the time when the terminal device detects the connection failure.

4. The apparatus according to claim 1, wherein, The determining unit determines the type of LTM connection failure according to the first report, including: if it is confirmed according to the first report that the terminal device has received the configuration information of the LTM candidate cell, and the terminal device detects a connection failure with the cell that sent the configuration information of the LTM candidate cell, and if the second information does not exist in the first report, or the time length indicated by the second information in the first report is greater than or equal to a first time threshold, the determining unit determines that the type of LTM connection failure corresponding to the first report is late LTM.

5. The apparatus according to claim 4, wherein, The first time threshold is used to indicate the threshold information of the connection duration between the terminal device and the second network device where the connection failure occurs; The first time threshold is predefined or configured by operation and maintenance management.

6. The apparatus according to claim 4, wherein, The late LTM means: the terminal device has received the first configuration information sent by the second network device where the connection failure occurs, and the first configuration information includes at least one LTM candidate cell information. Before the terminal device successfully receives the first message sent by the second network device, the terminal device detects a connection failure with the second network device, and the terminal device does not report the second information or the second information reported by the terminal device is greater than or equal to the first time threshold. The first message is used to instruct the terminal device to perform an LTM cell change. The determining unit determines the type of LTM connection failure according to the first report, including:

7. The apparatus according to claim 1, wherein, if it is confirmed according to the first report that the terminal device detects a connection failure with the LTM target cell, and if the time length indicated by the second information in the first report is less than or equal to a second time threshold, and the cell of the first reestablishment attempt or the cell of the first LTM recovery attempt of the terminal device is the cell where the terminal device receives the LTM cell change message or the cell where the terminal device receives the LTM initialization message, the determining unit determines that the type of LTM connection failure corresponding to the first report is early LTM. ​ 8. The apparatus according to claim 7, wherein, The second time threshold is used to indicate threshold information of the connection duration between the terminal device and the second network device where the connection failure occurs; The second time threshold is predefined or configured by operation and maintenance management.

9. The apparatus according to claim 7, wherein, The premature LTM means: Before the connection failure, the terminal device performs LTM cell change or LTM initialization, and the second information reported by the terminal device is less than or equal to the second time threshold, and the cell of the first reestablishment attempt or the cell of the first LTM recovery attempt is the cell where the terminal device receives the LTM cell change message or the cell where the terminal device receives the LTM initialization message.

10. The apparatus according to claim 1, wherein, The determining unit determines the type of LTM connection failure according to the first report, including: If it is confirmed according to the first report that the terminal device detects a connection failure with the LTM target cell, and If the time length indicated by the second information in the first report is less than or equal to the third time threshold, and the cell of the first reestablishment attempt or the cell of the first LTM recovery attempt of the terminal device is a cell other than the cell where the terminal device receives the LTM cell change message or the cell where the terminal device receives the LTM initialization message and the LTM target cell, The determining unit determines that the type of LTM connection failure corresponding to the first report is LTM to wrong cell.

11. The apparatus according to claim 10, wherein, The third time threshold is used to indicate threshold information of the connection duration between the terminal device and the second network device where the connection failure occurs; The third time threshold is predefined or configured by operation and maintenance management.

12. The apparatus according to claim 10, wherein, LTM to wrong cell means: Before the connection failure, the terminal device performs LTM cell change or LTM initialization, and the second information reported by the terminal device is less than or equal to the third time threshold, and the cell of the first reestablishment attempt or the cell of the first LTM recovery attempt of the terminal device is neither the cell where the terminal device receives the LTM cell change message or the LTM initialization message nor the cell where the terminal device detects the failure or the LTM target cell.

13. An apparatus for mobility management, configured in a terminal device, wherein, The device includes, a receiving unit that receives configuration information of LTM candidate cells; a generating unit that records LTM connection failure information in a first report when a connection failure occurs; a sending unit that sends the first report to a first network device, where the first report is used for the first network device to determine the type of LTM connection failure, and the type of LTM connection failure includes one of the following: late LTM, premature LTM or LTM to wrong cell.

14. The apparatus according to claim 13, wherein, The LTM connection failure information includes at least one of the following: first information used to indicate that the mobility type related to the connection failure is LTM; second information used to indicate the time length corresponding to the connection failure; third information used to indicate the cell where the connection failure occurs; fourth information used to indicate the type of the connection failure.

15. The apparatus according to claim 14, wherein, The time length is the time length from the last time the terminal device receives a handover command or the last time it receives a reconfiguration message or the last time it receives an LTM cell change message to the time when the terminal device detects the connection failure.

16. A network device, comprising a memory and a processor, the memory storing a computer program, the processor being configured to execute the computer program to implement the following method: Receiving a first report sent by a terminal device, the first report including LTM connection failure information; Determining, according to the first report, a type of LTM connection failure, the type of LTM connection failure including one of the following: late LTM, early LTM, or LTM to a wrong cell.

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