Indicating timing issues associated with uplink synchronization

Abstract

Disclosed is a method comprising receiving a successful handover report from a user equipment, the successful handover report indicating a successful inter-radio access technology handover of the user equipment from a source node to a target node, where the successful handover report indicates that a time threshold is exceeded during the successful inter-radio access technology handover, the time threshold is associated with monitoring of an uplink synchronization procedure between the user equipment and the target node; determining, based on the successful handover report, whether an exceeding of the time threshold is caused by a problem at the target node; and transmitting, to the source node or to a network entity different from the source node, information indicating at least one timing problem associated with an uplink synchronization procedure of at least a successful inter-radio access technology handover, based on determining that the exceeding of the time threshold is not caused by the problem at the target node.

Description

TECHNICAL FIELD

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

[0002] Mobility robustness optimization for handovers can involve analyzing radio link failures and other handover performance information, and creating failure statistics to improve handover success rates. There are challenges in how to collect the information needed for mobility robustness optimization. SUMMARY

[0003] The scope of protection sought for various example embodiments is set forth by the independent claims. Example embodiments and features that do not fall under the scope of the independent claims, if any, will be understood based on the description in the specification, which describes examples and features that are useful for understanding various embodiments.

[0004] According to one aspect, there is provided an apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to receive, from a user equipment, a successful handover report indicating a successful inter-radio access technology handover of the user equipment from a source node to a target node, the apparatus being associated with the target node, wherein the successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment and the target node; determine, based on the successful handover report, whether the exceeding of the time threshold was caused by a problem at the target node; and based on determining that the exceeding of the time threshold was not caused by the problem at the target node, send, to the source node or to a network entity different from the source node, information indicating at least one timing problem associated with at least the uplink synchronization procedure of the successful inter-radio access technology handover.

[0005] According to another aspect, there is provided an apparatus comprising means for receiving, from a user equipment, a successful handover report indicating a successful inter-radio access technology handover of the user equipment from a source node to a target node, the apparatus being associated with the target node, wherein the successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment and the target node; means for determining, based on the successful handover report, whether the exceeding of the time threshold was caused by a problem at the target node; and means for sending, based on determining that the exceeding of the time threshold was not caused by the problem at the target node, information indicating at least one timing problem associated with at least the uplink synchronization procedure of the successful inter-radio access technology handover, to the source node or to a network entity different from the source node.

[0006] According to another aspect, there is provided a method comprising: receiving, by an apparatus from a user equipment, a successful handover report, the successful handover report indicating a successful inter-radio access technology handover of the user equipment from a source node to a target node, the apparatus being associated with the target node, wherein the successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment and the target node; determining, by the apparatus based on the successful handover report, whether the exceeding of the time threshold was caused by a problem at the target node; and based on determining that the exceeding of the time threshold was not caused by a problem at the target node, sending, by the apparatus to the source node or to a network entity different from the source node, information indicating at least one timing problem, the at least one timing problem being associated with at least the uplink synchronization procedure of the successful inter-radio access technology handover.

[0007] According to another aspect, there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to at least: receive, from a user equipment, a successful handover report, the successful handover report indicating a successful inter-radio access technology handover of the user equipment from a source node to a target node, the apparatus being associated with the target node, wherein the successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment and the target node; determine, based on the successful handover report, whether the exceeding of the time threshold was caused by a problem at the target node; and based on determining that the exceeding of the time threshold was not caused by a problem at the target node, send, to the source node or to a network entity different from the source node, information indicating at least one timing problem, the at least one timing problem being associated with at least the uplink synchronization procedure of the successful inter-radio access technology handover.

[0008] According to another aspect, there is provided a computer readable medium comprising program instructions which, when executed by an apparatus, cause the apparatus to at least: receive, from a user equipment, a successful handover report, the successful handover report indicating a successful inter-radio access technology handover of the user equipment from a source node to a target node, the apparatus being associated with the target node, wherein the successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment and the target node; determine, based on the successful handover report, whether the exceeding of the time threshold was caused by a problem at the target node; and based on determining that the exceeding of the time threshold was not caused by a problem at the target node, send, to the source node or to a network entity different from the source node, information indicating at least one timing problem, the at least one timing problem being associated with at least the uplink synchronization procedure of the successful inter-radio access technology handover.

[0009] According to another aspect, there is provided a non-transitory computer- readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus to at least: receive, from a user equipment, a successful handover report, the successful handover report indicating a successful inter-radio access technology handover of the user equipment from a source node to a target node, the apparatus being associated with the target node, wherein the successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment and the target node; determine, based on the successful handover report, whether the exceeding of the time threshold was caused by a problem at the target node; and based on determining that the exceeding of the time threshold was not caused by the problem at the target node, send, to the source node or to a network entity different from the source node, information indicating at least one timing problem, the at least one timing problem being associated with at least an uplink synchronization procedure of the successful inter-radio access technology handover.

[0010] According to another aspect, there is provided an apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receive information indicating at least one timing problem, the at least one timing problem being associated with at least an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, the apparatus being associated with the source node, wherein the information is received from the target node; increment, based on the information, a counter; and send, to a network entity, counter information indicating a value of the counter.

[0011] According to another aspect, there is provided an apparatus comprising: means for receiving information indicating at least one timing problem, the at least one timing problem being associated with at least an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, the apparatus being associated with the source node, wherein the information is received from the target node; means for incrementing, based on the information, a counter; and means for sending, to a network entity, counter information indicating a value of the counter.

[0012] According to another aspect, there is provided a method comprising: receiving, by an apparatus, information indicating at least one timing problem, the at least one timing problem being associated with at least an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, the apparatus being associated with the source node, wherein the information is received from the target node; incrementing, by the apparatus, based on the information, a counter; and sending, by the apparatus, to a network entity, counter information indicating a value of the counter.

[0013] According to another aspect, there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to at least: receive information indicative of at least one timing problem, the at least one timing problem being associated with at least one successful uplink synchronization procedure of at least one user equipment from a source node to a target node, the apparatus being associated with the source node, wherein the information is received from the target node; increment a counter based on the information; and send, to a network entity, counter information indicative of a value of the counter.

[0014] According to another aspect, there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to at least: receive information indicative of at least one timing problem, the at least one timing problem being associated with at least one successful uplink synchronization procedure of at least one user equipment from a source node to a target node, the apparatus being associated with the source node, wherein the information is received from the target node; increment a counter based on the information; and send, to a network entity, counter information indicative of a value of the counter.

[0015] According to another aspect, there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to at least: receive information indicative of at least one timing problem, the at least one timing problem being associated with at least one successful uplink synchronization procedure of at least one user equipment from a source node to a target node, the apparatus being associated with the source node, wherein the information is received from the target node; increment a counter based on the information; and send, to a network entity, counter information indicative of a value of the counter.

[0016] According to another aspect, there is provided an apparatus comprising: at least one processor and at least one memory storing instructions which, when executed by the at least one processor, cause the apparatus to at least: receive information indicative of at least one timing problem, the at least one timing problem being associated with at least one successful uplink synchronization procedure of at least one user equipment from a source node to a target node, wherein the information is received from the target node or the source node; and optimize, based at least in part on the information, one or more radio measurement thresholds associated with triggering a handover from the source node to the target node.

[0017] According to another aspect, there is provided an apparatus comprising: means for receiving information indicative of at least one timing issue associated with an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, wherein the information is received from the target node or the source node; and means for optimizing one or more radio measurement thresholds associated with triggering a handover from the source node to the target node based at least in part on the information.

[0018] According to another aspect, there is provided a method comprising: receiving information indicative of at least one timing issue associated with an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, wherein the information is received from the target node or the source node; and optimizing one or more radio measurement thresholds associated with triggering a handover from the source node to the target node based at least in part on the information.

[0019] According to another aspect, there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: receiving information indicative of at least one timing issue associated with an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, wherein the information is received from the target node or the source node; and optimizing one or more radio measurement thresholds associated with triggering a handover from the source node to the target node based at least in part on the information.

[0020] According to another aspect, there is provided a computer readable medium comprising program instructions which, when executed by an apparatus, cause the apparatus to perform at least the following: receiving information indicative of at least one timing issue associated with an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, wherein the information is received from the target node or the source node; and optimizing one or more radio measurement thresholds associated with triggering a handover from the source node to the target node based at least in part on the information.

[0021] According to another aspect, there is provided a non-transitory computer- readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus to perform at least the following: receive information indicative of at least one timing issue associated with at least one successful inter-radio access technology handover of at least one user equipment from a source node to a target node, wherein the information is received from the target node or the source node; and optimize one or more radio measurement thresholds associated with triggering a handover from the source node to the target node based at least in part on the information. BRIEF DESCRIPTION OF DRAWINGS

[0022] In the following, various example embodiments will be described in more detail with reference to the accompanying drawings, in which: Figure 1A An example of a wireless communication network is shown; Figure 1A An example of a system is shown; Figure 2 A signal flow diagram is shown; Figure 3 A signal flow diagram is shown; Figure 4 A flow chart is shown; Figure 5 A flow chart is shown; Figure 6 A flow chart is shown; Figure 7 A flow chart is shown; Figure 8 An example of an apparatus is shown; and Figure 9 An example of an apparatus is shown. DETAILED DESCRIPTION

[0023] The following embodiments are examples. Although the specification can

[0024] Some example embodiments described herein can be implemented in a wireless communication network comprising a radio access network based on one or more of the following radio access technologies: Global System for Mobile Communications (GSM) or any other second generation radio access technology, Universal Mobile Telecommunication System (UMTS, 3G) based on Basic Wideband Code Division Multiple Access (W-CDMA), High-Speed Packet Access (HSPA), Long Term Evolution (LTE), LTE-Advanced, Fourth Generation (4G), Fifth Generation (5G), 5G New Radio (NR), 5G Advanced (i.e., 3GPP NR Rel-18 and beyond), or Sixth Generation (6G). Some examples of radio access networks include Universal Mobile Telecommunication System (UMTS) Radio Access Network (UTRAN), Evolved Universal Terrestrial Radio Access Network (E-UTRAN), or Next Generation Radio Access Network (NG-RAN). The wireless communication network can also comprise a core network, and some example embodiments can also be applied to network functions of the core network.

[0025] It should be noted that the embodiments are not restricted to the wireless communication networks that are given as examples, but a person skilled in the art can apply the solution to other wireless communication networks or systems with necessary properties. For example, some example embodiments can also be applied to a communication system based on IEEE 802.11 specifications or to a communication system based on IEEE 802.15 specifications.

[0026] Figure 1A An example of a simplified wireless communication network showing some physical and logical entities is depicted. Figure 1A The connections shown in the Figure 1A The wireless communication network can also comprise other physical and logical entities than the ones shown in the

[0027] However, the example embodiments described herein are not restricted to the wireless communication networks that are given as examples, but a person skilled in the art can apply the embodiments described herein to other wireless communication networks having necessary properties.

[0028] Figure 1A The example wireless communication network shown in the

[0029] Figure 1AA user equipment (UE) 100, 102 configured to wirelessly connect with an access node (AN) 104 of an access network over one or more communication channels in a radio cell is shown. The AN 104 can be an evolved NodeB (abbreviated as eNB or eNodeB), or a next generation evolved NodeB (abbreviated as ng-eNB), or a next generation NodeB (abbreviated as gNB or gNodeB) providing the radio cell. The wireless connection (e.g., radio link) from the UE to the access node 104 can be referred to as uplink (UL) or reverse link, and the wireless connection (e.g., radio link) from the access node to the UE can be referred to as downlink (DL) or forward link. The UE 100 can also communicate directly with the UE 102 via a wireless connection commonly referred to as a sidelink (SL), and vice versa. It should be appreciated that the access node 104 or its functionalities can be implemented by using any entity, host, server or access point, etc. suitable for providing such functionalities.

[0030] The access network can comprise more than one access node, in which case the access nodes can also be configured to communicate with each other over wired or wireless links. These links between access nodes can be used for transmitting and receiving control plane signaling and also for routing data from one access node to another.

[0031] The access node can comprise a computing device configured to control radio resources of the access node. The access node can also be referred to as a base station, base transceiver station (BTS), access point, cell site, radio access node, or any other type of node capable of wireless connection with a UE (e.g., UE 100, UE 102). The access node can comprise or be coupled to a transceiver. A connection can be provided from the transceiver of the access node to an antenna unit, which establishes bi-directional radio links to the UE 100, UE 102. The antenna unit can comprise an antenna or antenna element, or multiple antennas or antenna elements.

[0032] The access node 104 can also be connected to a core network (CN) 110. The core network 110 can comprise an evolved packet core (EPC) network and / or a fifth generation core network (5GC). The EPC can comprise network entities such as a serving gateway (S-GW for routing and forwarding data packets), a packet data network gateway (P-GW) for providing connectivity to external packet data networks for UEs, and a mobility management entity (MME). The 5GC can comprise network functions such as a user plane function (UPF), an access and mobility management function (AMF), and a location management function (LMF).

[0033] The core network 110 can also be able to communicate with one or more external networks 113, such as a public switched telephone network or the Internet, or utilize services provided by them. For example, in a 5G wireless communication network, a UPF of the core network 110 can be configured to communicate with an external data network via an N6 interface. In an LTE wireless communication network, a P-GW of the core network 110 can be configured to communicate with an external data network.

[0034] The UEs 100, 102 shown are one type of apparatus to which the resource allocation and assignment can be applied. The UEs 100, 102 can also be referred to as wireless communication devices, subscriber units, mobile stations, remote terminals, access terminals, user terminals, terminal devices, or user equipment, to name a few. UEs can be computing devices operating with or without a subscriber identification module (SIM), including but not limited to the following types of computing devices: mobile phones, smartphones, personal digital assistants (PDAs), hand-held devices, computing devices including wireless modems (e.g., alarm or meter devices, etc.), laptop computers, desktop computers, tablet computers, game consoles, notebooks, multimedia devices, RedCap devices, wearable devices with radio parts (e.g., watches, headsets, or glasses), sensors including wireless modems, or any computing device including a wireless modem integrated in a vehicle.

[0035] It should be appreciated that a UE can also be a nearly exclusive uplink only device, an example of which can be a camera or video camera that loads images or video clips to a network. A UE can also be a device with the ability to operate in an Internet of Things (IoT) network, which is a scenario in which objects are provided with the ability to transfer data over a network rather than a human-to-human or human-to-computer interaction ability. A UE can also utilize the cloud. In some applications, computation can be performed in the cloud or in another UE.

[0036] The wireless communication network can also be able to support the use of cloud services, for example, at least a part of the core network operations can be performed as a cloud service (this is depicted by the “cloud” 114 in Figure 1A The wireless communication network can also include a central control entity or the like, providing facilities for wireless communication networks of different operators to cooperate, for example, in spectrum sharing.

[0037] 5G enables the use of multiple input multiple output (MIMO) antennas in the access nodes 104 and / or UEs 100, 102, more base stations or access nodes than LTE networks (the so-called concept of small small cells), including macro sites operating in co-operation with smaller stations and, depending on the service demands, use cases and / or available frequency spectra, employing a variety of radio technologies. The 5G wireless communications networks can support a wide range of use cases and related applications, including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications, such as (massive) machine type communications (mMTC), including vehicle safety, different sensors and real-time control.

[0038] In 5G wireless communications networks, the access nodes and / or UEs can have multiple radio interfaces, i.e. sub-6 GHz, cmWave and mmWave, and can also be integrated with existing legacy radio access technologies, such as LTE. The integration with LTE can be implemented, for example, in a system where macro coverage can be provided by LTE and 5G radio interface access can come from small small cells by aggregation to LTE. In other words, 5G wireless communications networks can support inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as sub-6 GHz-cmWave-mmWave). One of the concepts considered to be used in 5G wireless communications networks can be network slicing, where multiple independent and dedicated virtual sub-networks (network instances) can be created within the substantially same infrastructure to run services with different requirements on latency, reliability, throughput and mobility.

[0039] In some example embodiments, an access node (e.g. access node 104) can comprise a radio unit (RU) comprising a radio transceiver (TRX), i.e. transmitter (Tx) and receiver (Rx), one or more distributed units (DU) 105, which can be used for so-called first layer (LI) and real-time second layer (L2) processing, and a central unit (CU) 108 (also referred to as centralized unit), which can be used for non-real-time L2 and third layer (L3) processing. The CU 108 can be connected to one or more DUs 105, e.g. via an Fl interface. This embodiment of an access node can enable centralization of the CU with respect to the cell site and the DUs, which can be more distributed and can even be kept at the cell site. The CU and the DUs together can also be referred to as baseband or baseband unit (BBU). The CU and the DUs can also be comprised in a radio access point (RAP).

[0040] The CU 108 can be a logical node that hosts the radio resource control (RRC), service data adaptation protocol (SDAP), and / or packet data convergence protocol (PDCP) of the NR protocol stack for the access node. The DU 105 can be a logical node that hosts the radio link control (RLC), medium access control (MAC), and / or physical (PHY) layer of the NR protocol stack for the access node. Operation of the DU can be controlled at least in part by the CU. It should also be understood that the distribution of functions between the DU 105 and the CU 108 can vary depending on implementation. The CU can include a control plane (CU-CP) that can be a logical node that hosts the control plane portion of the RRC and PDCP protocols of the NR protocol stack for the access node. The CU can also include a user plane (CU-UP) that can be a logical node that hosts the user plane portion of the PDCP and SDAP protocols of the CU for the access node.

[0041] The cloud computing system can also be used to provide the CU 108 and / or the DU 105. The CU provided by the cloud computing system can be referred to as a virtualized CU (vCU). In addition to the vCU, there can also be a virtualized DU (vDU) provided by the cloud computing system. Further, there can also be a combination in which the DU can be implemented on a so-called bare-metal solution, such as an application-specific integrated circuit (ASIC) or customer-specific standard product (CSSP) system on a chip (SoC).

[0042] The edge cloud can be brought into the access network (e.g., RAN) by utilizing network function virtualization (NFV) and software-defined networking (SDN). Using the edge cloud can mean that at least a portion of the access node operations are executed in a computing system that is operably coupled to a remote radio head (RRH) or radio unit (RU) of the access node. The access node operations can also be executed on a distributed computing system or a cloud computing system that is located at the access node. Application of the cloud RAN architecture enables RAN real-time functions to be executed at the access network (e.g., in the DU 105) and non-real-time functions to be executed in a centralized manner (e.g., in the CU 108).

[0043] It should also be understood that the distribution of functions between the core network operations and the access node operations can be different, or even non-existent, in future wireless communication networks compared to LTE or 5G. Some other technology advancements that can be used include big data and all-IP, which can change the way wireless communication networks are constructed and managed. The 5G (or New Radio, NR) wireless communication network can support multiple tiers in which a multi-access edge computing (MEC) server can be placed between the core network 110 and the access node 104. It should be understood that MEC can also be applied in LTE wireless communication networks.

[0044] A 5G wireless communication network ("5G network") can also include non-terrestrial communication networks, such as satellite communication networks, to enhance or complement the coverage of the 5G radio access network. For example, satellite communication can support data transmission between the 5G radio access network and the core network, thereby enabling more extensive network coverage. Possible use cases can be to provide service continuity for machine-to-machine (M2M) or Internet of Things (IoT) devices or for passengers on board vehicles, or to ensure service availability for critical communications and future railway / maritime / aeronautical communications. Satellite communication can utilize geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular large constellations (systems deploying hundreds of (nano)satellites). A given satellite 106 in a large constellation can cover several satellite-enabled network entities that create terrestrial cells. The terrestrial cells can be created through terrestrial relay access nodes or through access nodes 104 located on the ground or in satellites.

[0045] It will be apparent to those skilled in the art that, Figure 1A The access nodes 104 depicted are examples of parts of an access network (e.g., a radio access network), and in practice, the access network can comprise multiple access nodes, the UEs 100, 102 can access multiple radio cells, and the access network can also comprise other apparatuses, such as physical layer relay access nodes or other entities. At least one of the access nodes can be a Home eNodeB or a Home gNodeB. A Home gNodeB or a Home eNodeB is a kind of access node that can be used to provide indoor coverage within a home, office, or other indoor environment.

[0046] In addition, in the geographical area of an access network (e.g., a radio access network), multiple radio cells of different kinds can be provided as well as multiple radio cells. A radio cell can be a macro cell (or umbrella cell), which can be a large-sized cell with a diameter of up to tens of kilometers, or smaller cells, such as micro, femto, or pico cells. Figure 1A The access nodes of the present disclosure can provide any kind of these cells. A cellular radio network can be implemented as a multi-tiered access network comprising several kinds of radio cells. In a multi-tiered access network, one access node can provide one kind of radio cell or multiple radio cells, and thus multiple access nodes can be needed to provide such a multi-tiered access network.

[0047] To meet the need for improving the performance of the access network, the concept of a "plug and play" access node can be introduced. In addition to a Home eNodeB or a Home gNodeB, an access network capable of using "plug and play" access nodes can comprise a Home NodeB gateway or HNB GW (not depicted). Figure 1AA HNB-GW, which can be installed within an operator's access network, can aggregate traffic from a large number of home eNodeBs or home gNodeBs back to the operator's core network.

[0048] Handover (also known as handoff or cell change) is a procedure in wireless communication networks in which an active connection between a UE 100, UE 102 and its serving base station 104 is transferred from one cell to another. The handover procedure enables a seamless and continuous communication experience for a user as the user moves through different coverage areas within the network.

[0049] Figure 1A An example of a system on which some example embodiments can be applied is shown. Figure 1B It can be understood as depicting a part of a wireless communication network, Figure 1B but with greater accuracy with respect to mobility scenarios. The system comprises a network manager 111, a UE 100 and a plurality of network nodes 104, 104B (e.g. gNB or eNB or ng-eNB) providing a plurality of cells 121, 122.

[0050] With reference to Figure 1A During handover, the connection of the UE 100 is switched from a current serving cell 121 provided by a source node 104 to a target cell 122 provided by a target node 104B while preserving an ongoing voice call or data session.

[0051] The handover procedure can be initiated by the network (e.g. source node 104) when certain predefined conditions are met, such as when the signal quality of a neighboring cell 122 becomes significantly better than the signal quality of the current serving cell 121. The decision to perform handover can be based on various factors, including radio measurements (such as Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ)), network load, user mobility and network configuration parameters.

[0052] Upon initiating the handover procedure, the network (e.g. source node 104) can send a handover command to the UE 100, which can include information about the target cell 122 and any required configuration parameters. The UE 100 can then establish a connection with the target node 104B providing the target cell 122, synchronize its timing and frequency, and exchange control information to confirm successful completion of the handover. Once the handover is completed, the UE 100 releases its connection with the previous serving cell 121 and communication continues through the new serving cell 122.

[0053] The handover can be an intra-radio access technology (intra-RAT) handover or an inter-radio access technology (inter-RAT) handover.

[0054] Intra-RAT handover means that the source cell 121 and the target cell 122 are based on the same radio access technology. For example, in an intra-NR handover, both the source node 104 and the target node 104B can be gNBs.

[0055] Inter-RAT handover means that the source cell 121 and the target cell 122 are based on different radio access technologies. For example, in an inter-RAT handover, the source node 104 can be an eNB or ng-eNB (4G base station) and the target node 104B can be a gNB (5G base station), or vice versa.

[0056] The network manager (NM) 111 provides a grouping of end-user functions responsible for managing the network. The network manager 111 can be a separate network entity connected to the source node 104 and / or the target node 104B.

[0057] For example, the network manager 111 can comprise a self-organizing network (SON) function hosted in a network management system (NMS) or an operation, administration, and maintenance (OAM) system, where mobility robustness optimization (MRO) counters can be analyzed and post-processed. The MRO counters can be received by a performance management (PM) part of the NMS from the source node 104 and / or the target node 104B via Itf-N (so-called northbound interface). The PM part of the NMS can forward these MRO counters to the SON function in the NMS. The SON function can then send corrections to a configuration management (CM) part of the NMS, which can reconfigure corresponding handover parameters in the RAN (i.e., the source node 104).

[0058] MRO is a SON function that can be used in wireless communication networks to improve handover performance and overall network mobility. MRO aims to minimize handover-related problems, such as early handover, delayed handover, and handover failure, by automatically adjusting and optimizing handover parameters of the network based on observed network performance and user mobility patterns.

[0059] MRO works by continuously monitoring and collecting relevant performance metrics from the network (e.g., from the source node 104 and the target node 104B), including handover success rates, radio link failure (RLF) reports, and other key performance indicators (KPIs). These metrics can subsequently be analyzed to identify any handover-related problems and determine potential causes for such problems, such as incorrect handover parameter settings or suboptimal cell coverage.

[0060] Once the potential cause of the handover issue has been identified, the MRO function can adjust relevant handover parameters in a given cell pair (e.g., source cell 121 and target cell 122), such as handover trigger thresholds, time-to-trigger (TTT) values, and hysteresis margins, to optimize handover performance. The MRO function can iteratively update these parameters, constantly learning from the network’s performance to maintain optimal handover settings.

[0061] For 3GPP NR Rel-17 for intra-NR mobility, the RLF-based MRO concept has been extended to log mobility situations where there was a risk or failure but recovery, which ultimately resulted in a successful handover by providing a successful handover report (SHR).

[0062] A successful handover report is a message or collection of data generated by the UE after a successful handover procedure is completed. The report provides information to the network about the handover performance. The successful handover report helps the network analyze the performance of the handover, identify potential issues or areas for improvement, and optimize network performance, coverage, and reliability.

[0063] For example, a successful handover report can include at least one of the following: the identities of the source cell 121 and target cell 122 of the handover, location information of the UE 100, latest radio link measurements identified by measurements available at the time of performing the handover, a cause indicating the trigger for generating the SHR (e.g., t310 cause, t312 cause, or t304 cause), latest radio measurements of candidate target cells in case of conditional handover, time elapsed between conditional handover execution towards a target cell 122 and corresponding latest configuration received for the selected target cell 122, cell radio network temporary identifier (C-RNTI) of the UE 100 in the target cell 122, user plane interruption time at handover involving dual active protocol stack (DAPS) handover, RA-InfoCommon in case T304 is above a threshold, and / or a flag indicating that RLF was detected in the source cell during DAPS handover.

[0064] For 3GPP NR Rel-18, the SHR concept can be extended to inter-RAT mobility (e.g., handover between LTE and 5G NR). For inter-RAT handover from an NR cell to an LTE cell, a successful handover report can be triggered, for example, by T310 or T312 criteria (e.g., by T310 or T312 SHR percentage thresholds being exceeded). For inter-RAT handover from an LTE cell to an NR cell, a successful handover report can be triggered, for example, by T304 criteria (e.g., by T304 SHR percentage thresholds being exceeded).

[0065] The T304 timer can be started upon reception of the RRC connection reconfiguration message including the mobility control information message. The T304 timer can be stopped according to the following criteria: handover to 5G radio access (5GRA) is successfully completed, or handover to 5GRA. Upon expiry of the T304 timer, in case of an intra-frame 5GRA handover, the UE can initiate the RRC connection re-establishment procedure.

[0066] The T304 SHR percentage threshold (thresholdPercentageT304) is a time threshold that can include a certain portion or ratio or percentage of the configured T304 value. For example, if the T304 value is configured to 10 seconds, the T304 SHR percentage threshold can be set to 50% of the T304 value, i.e. 5 seconds. The T304 SHR percentage threshold can also be referred to herein as a T304 SHR portion threshold or a T304 SHR ratio threshold.

[0067] The T304 SHR percentage threshold can be used to sense uplink synchronization or random access procedure performance towards the target NR cell. Exceeding the T304 SHR percentage threshold triggering the SHR indicates that the uplink synchronization or random access procedure is not performed as fast as expected. However, the problem with the more persistent synchronization procedure towards the target NR node can be caused by a random access problem at the target NR node 104B or by suboptimal handover parameters configured at the LTE source node 104.

[0068] The random access procedure allows the UE 100 to establish an initial connection with the target node 104B. The random access procedure can also be referred to as initial access or random access channel (RACH) procedure.

[0069] According to the MRO concept, the source node 104 triggering the handover should be responsible for the failure analysis or problem analysis. In this case, it can be desirable to forward the SHR to the source LTE node 104 last serving the LTE source cell 121.

[0070] However, it can also be desirable to keep the impact on the LTE standard as small as possible. Therefore, the root cause analysis of the SHR triggered by the exceeding of the T304 SHR percentage threshold can be performed at the target NR node 104B to which the SHR can be reported.

[0071] Forwarding the SHR to the source LTE node 104 without processing would shift the complete root cause analysis procedure, including the check for NR-based random access problems, to the source LTE node 104, which can be undesirable. Furthermore, the SHR (encoded in NR format) can be forwarded to the source ng-eNB 104 as a container which cannot be read by the source ng-eNB 104 even in case of an intra-system inter-RAT handover.

[0072] Accordingly, there is a need for a method that can use SHR to support MRO while keeping the impact on the LTE standard as small as possible.

[0073] Some example embodiments can provide such a method that has no or low impact on the LTE standard. The method can be applied to intra-system inter-RAT handover or for inter-system inter-RAT handover.

[0074] Intra-system means that both the source node 104 and the target node 104B are connected to the same core network 110 of a radio access technology (e.g., 5G core). This allows the handover to be performed via communications completed over the Xn interface interconnecting the gNB (e.g., target node) and the ng-eNB (e.g., source node). The ng-eNB is an enhanced eNB that is capable of communicating with the 5G core but still provides E-UTRA user plane and control plane termination to the UE.

[0075] Inter-system means that the gNB (e.g., target node) is connected to the 5G core and the eNB (e.g., source node) is connected to the 4G core. In this case, the gNB and eNB can not be interconnected via any interface. The gNB can be directly connected to the 5G core via Ng and the eNB can be directly connected to the 4G core via the S1 interface. The inter-RAT handover can then be S1-based (if it is from LTE to NR) or NG-based (if it is from NR to LTE).

[0076] Some example embodiments can involve mobility robustness optimization by SHR (e.g., triggered by a T304 SHR percentage threshold being exceeded) where the SHR can be reported to the target NR node 104B for inter-RAT handover from the source LTE node 104 to the target NR node 104B.

[0077] Some example embodiments can enable utilization of an inter-RAT handover triggered (e.g., T304 SHR percentage threshold exceeded) SHR from LTE to NR as part of an MRO use case that requests optimization of radio measurement thresholds that trigger a handover in a source LTE node 104 towards a target NR node 104B. A basic root cause analysis (RCA) can be performed at the target NR node 104B of the inter-RAT handover under consideration, with random access problems being first ruled out. This analysis can be based on the random access report included in the SHR. The SON or MRO function responsible for the RCA at the target NR node 104B can decide whether a longer duration synchronization procedure (e.g., indicated by the T304 SHR percentage threshold being exceeded) is caused by random access problems (e.g., RACH misconfiguration) at the target NR node 104B or by suboptimal inter-RAT handover parameter settings at the source LTE node 104, which caused the handover to be triggered prematurely when the target NR cell 122 was not yet stable enough for the UE 100.

[0078] If the cause is random access problems (e.g., RACH misconfiguration) at the target NR node 104B, then MRO can be ruled out and there is no need to inform the source LTE node 104. However, if the cause is suboptimal inter-RAT handover parameter settings at the source LTE node 104, then it can be necessary to adjust the inter-RAT handover parameters at the source LTE node 104.

[0079] It should be noted that some example embodiments are not limited to LTE and NR, or in particular to handovers from LTE to NR, and they can apply to inter-RAT handovers between any two different radio access technologies.

[0080] Figure 1B A signal flow diagram is shown in accordance with example embodiments.

[0081] In this example embodiment, after the root cause analysis when a successful handover reporting decision MRO (i.e. the cause of the random access problem is determined to be suboptimal handover parameters at the source LTE node 104), the corresponding inter-RAT MRO function at the target NR node 104B counts handovers where the T304 SHR percentage threshold is exceeded within a given measurement period for a given source LTE and target NR cell pair (cell 121, cell 122). Thus, the target NR node 104B can share this information via the Itf-N interface from the target NR node 104B to the PM instance of the common network management system 111 (across both LTE and NR) in the form of performance measurements in a performance management (PM) file, which can therefore forward the counter data to the central MRO entity for optimization of the radio measurement thresholds that triggered the handover from the given source LTE cell 121 to the given target NR cell 122.

[0082] Referring to Figure 2 At 201, a source node 104 (e.g., ng-eNB or eNB) sends a handover command to the UE 100, the handover command including a configuration for successful handover reporting. For example, the configuration can indicate that the UE 100 store a successful handover report if a T304 SHR percentage threshold is exceeded. The UE 100 receives the configuration from the source node 104. During this configuration, the source node 104 can be a serving node for the UE 100. The source node 104 can also be referred to herein as a first network node.

[0083] At 202, the UE 100 completes a successful inter-RAT handover of the UE 100 from the source node 104 to a target node 104B (e.g., gNB). However, a T304 SHR percentage threshold is exceeded during the successful inter-RAT handover. The target node 104B can also be referred to herein as a second network node.

[0084] The target node 104B is associated with a radio access technology that is different from a radio access technology associated with the source node 104. For example, the source node 104 can be associated with a fourth generation cellular radio access technology (e.g., Long Term Evolution (LTE) or LTE-Advanced), and the target node 104B can be associated with a fifth generation cellular radio access technology (e.g., 5G New Radio).

[0085] At 203, the UE 100 stores a successful handover report indicating a successful inter-RAT handover of the UE 100 from the source node 104 to the target node 104B. For example, the SHR can be generated due to the T304 SHR percentage threshold being exceeded. The T304 SHR percentage threshold (thresholdPercentageT304) is a time threshold that can include a certain portion or ratio or percentage of a configured T304 value. For example, if the T304 value is configured to be 10 seconds, the T304 SHR percentage threshold can be set to 50% of the T304 value, i.e., 5 seconds. The T304 SHR percentage threshold can also be referred to herein as a T304 SHR portion threshold or a T304 SHR ratio threshold.

[0086] In other words, the inter-RAT handover from the source node to the target node is successful, but the UE stores the SHR due to the T304 SHR percentage threshold being exceeded during the inter-RAT handover.

[0087] For example, the successful handover report can be stored in an internal memory of the UE 100.

[0088] At 204, the UE 100 can send an indication to the target node 104B indicating availability of the successful handover report. For example, the indication can include a “successHO-InfoAvailable” flag sent in an RRCReconfigurationComplete message.

[0089] At 205, based on receiving the indication, the target node 104B can send a request to the UE 100 for providing the successful handover report. For example, the request can be sent in a UEInformationRequest message.

[0090] At 206, the UE 100 sends the successful handover report to the target node 104B. The UE 100 can send the successful handover report based on receiving the request from the target node 104B. For example, the successful handover report can be sent in a UEInformationResponse message. The target node 104B receives the successful handover report from the UE 100.

[0091] In other words, the target node 104B can obtain the successful handover report message from the UE 100 via the UEInformationRequest and UEInformationResponse procedures.

[0092] A successful handover report can include information indicating an identity of a source cell 121 provided by the source node 104 from a LTE cell and an identity of a target cell 122 (i.e., a current NR cell) provided by the target node 104B. The successful handover report can also identify the handover as an inter-radio access technology handover (e.g., from LTE to NR).

[0093] The successful handover report also indicates that a time threshold (e.g., thresholdPercentageT304) associated with an uplink synchronization procedure between the UE 100 and the target node 104B was exceeded during the successful inter-radio access technology handover, resulting in a timing issue associated with the uplink synchronization procedure. The uplink synchronization procedure can be part of a random access procedure between the UE 100 and the target node 104B. In other words, the random access procedure between the UE 100 and the target node 104B took longer than expected.

[0094] The successful handover report can be encoded in a format associated with a fifth generation cellular radio access technology (e.g., 5G NR).

[0095] At 207, the target node 104B determines, based on the successful handover report, whether the exceeding of the time threshold was caused by an issue at the target node 104B (e.g., a random access issue such as a RACH misconfiguration).

[0096] In other words, based on the knowledge that the SHR was triggered due to T304, the target node 104B starts a root cause analysis based on the random access report included in the SHR, as indicated in the SHR. The cause can be, for example, weak radio link conditions (i.e., the handover was initiated too early at the source node 104), or a RACH misconfiguration at the target node 104B.

[0097] At 208, based on determining that the exceeding of the time threshold was not caused by an issue at the target node 104B (i.e., based on determining that the timing issue was caused by the source node 104 due to an early decision for the successful inter-radio access technology handover), the target node 104B increments a counter that indicates a number of successful inter-radio access technology handovers from the source node to the target node, the number of successful inter-radio access technology handovers being associated with at least one timing issue.

[0098] Alternatively, if the target node 104B determines that the exceeding of the time threshold was caused by an issue at the target node (e.g., a RACH misconfiguration), the target node 104B can consider it as an event related to random access optimization in the target cell 122 for the target node 104B.

[0099] At 209, the target node 104B sends information to a network entity, such as the network manager 111 (or the PM part of the NMS or a SON entity), wherein the information comprises the counter information indicating the number of successful inter-radio access technology handovers from the source node to the target node within the predefined time period, the number of successful inter-radio access technology handovers being associated with timing problems. The SON entity of the network management system 111 receives the counter information. The SON entity of the network management system 111 can comprise a mobility robustness optimization functionality.

[0100] Thus, the counter information can indicate at least one timing problem associated with at least one successful uplink synchronization procedure of at least one inter-radio access technology handover of at least one user equipment 100 from the source node 104 to the target node 104B.

[0101] For example, the target node 104B can send the counter information at the end of the predefined time period. In other words, at the end of the measurement period of the cell pair comprising the source cell 121 and the target cell 122, a new PM counter (i.e. the number of successful inter-RAT handovers associated with timing problems involving uplink synchronization) can be reported (e.g. via the Itf-N interface) from the target node 104B to the network manager 111.

[0102] This new PM counter can also be referred to as the number of almost too early handovers. "Almost too early" means that the RLF does not follow within a predetermined time interval after the handover, but at least one disturbance of the handover is observed. The at least one disturbance can mean that the uplink synchronization procedure (or random access procedure) lasts longer than a predefined time threshold, so that the handover was risky.

[0103] On the other hand, "too early handover" can mean that the T304 expires or the RLF occurs within a predetermined time interval after the handover.

[0104] "Almost too early handover" can also be referred to as "too early inter-RAT handover without RLF".

[0105] At 210, the network manager 111 (or the SON entity of the NMS) optimizes one or more radio measurement thresholds associated with triggering the handover from the source node to the target node based at least in part on the counter information. For example, the optimization can be performed if the number of successful inter-radio access technology handovers associated with timing problems is above a threshold.

[0106] In other words, based on the new PM counter (i.e. the number of successful inter-RAT handovers associated with timing issues related to uplink synchronization), which can be part of the KPI, e.g. given as the ratio of the new PM counter to the total number of successful handovers from the source node to the target node, and possibly other rules specific to the operator, the network manager 111 (or SON entity) can initiate MRO optimization of the source cell 121 for the radio measurement threshold(s) used to trigger handover from the source cell 121 (e.g. LTE cell) to the target cell 122 (e.g. NR cell).

[0107] The optimization can also be based on the number of inter-radio access technology handovers from the source node to the target node that were too early and caused radio link failure within a predefined time period. In other words, in this case, the network manager 211 (or SON entity) can combine or merge the number of “almost too early handovers” and “too early handovers”. For example, “too early handovers” can be reported from the source node 104.

[0108] At 211, the network manager 111 (or CM part of the NMS or SON entity) sends an indication to the source node 104 indicating the optimized radio measurement threshold(s). In other words, the possible change of the radio measurement threshold(s) used to trigger handover from the source cell 121 to the target cell 122 is communicated to the source node 104. Thus, there can be no new communication from the NR to the LTE side to provide this optimization.

[0109] The source node 104 can then apply the optimized radio measurement threshold(s) to subsequent handovers from the source node 104 to the target node 104B. The optimized radio measurement threshold(s) can help to avoid or reduce timing issues associated with uplink synchronization procedures during subsequent handovers.

[0110] Figure 2 An advantage of the example embodiment is that there is no impact on the LTE standard and it enables common operation, administration and maintenance (OAM) for NR and LTE, e.g. for the case of intra-system inter-RAT handover.

[0111] Figure 2 A signal flow diagram according to an example embodiment is shown.

[0112] In this example embodiment, upon root cause analysis at the target NR node 104B at the time of a successful handover reporting decision MRO (i.e. the cause of the random access problem is determined to be suboptimal handover parameters at the source LTE node 104), the corresponding inter-RAT MRO function at the target NR node 104B can send a message to the source LTE node 104 serving the outgoing source LTE cell 121, where the message can include a new handover reporting type information element referred to as, for example, "almost too early inter-RAT handover".

[0113] Based on the indication of "almost too early inter-RAT handover", the MRO function at the source LTE node 104 serving the source LTE cell 121 can generate a new cell pair specific MRO counter, which can be referred to as, for example, "almost too early inter-RAT HO" for the inter-RAT cell pair in question (cell 121, cell 122).

[0114] Alternatively, the MRO function at the source LTE node 104 can handle the information (i.e. the indication of "almost too early inter-RAT handover") in a weighted manner within the generation of the "too early inter-RAT HO" counter derived from the RLF reports of the inter-RAT cell pair in question (cell 121, cell 122).

[0115] The counter value can then be reported at the end of the measurement period to, for example, a central MRO instance in the OAM domain, such as to the network manager 111 (e.g. via the Itf-N interface).

[0116] "Almost too early handover" means that the RLF does not follow within a predetermined time interval after the handover, but at least one disturbance of the handover is observed. At least one disturbance can mean that the uplink synchronization procedure (or random access procedure) lasts longer than a predefined time threshold, so that the handover is at risk.

[0117] "Too early" handover can mean that the RLF occurs within a predetermined time interval after the handover.

[0118] "Almost too early handover" can also be referred to as "too early inter-RAT handover without RLF".

[0119] Reference is made to Figure 3 At 301, a source node 104 (e.g., ng-eNB or eNB) sends a handover command to a UE 100 including a configuration for successful handover reporting. For example, the configuration can instruct the UE 100 to store a successful handover report if a T304 SHR percentage threshold is exceeded. The UE 100 receives the configuration from the source node 104. During this configuration, the source node 104 can be a serving node for the UE 100. The source node 104 can also be referred to herein as a first network node.

[0120] At 302, the UE 100 completes a successful inter-RAT handover of the UE 100 from the source node 104 to the target node 104B (e.g., gNB). However, a T304 SHR percentage threshold is exceeded during the successful inter-RAT handover. The target node 104B can also be referred to herein as a second network node.

[0121] The target node 104B is associated with a radio access technology that is different from a radio access technology associated with the source node 104. For example, the source node 104 can be associated with a fourth generation cellular radio access technology (e.g., Long Term Evolution (LTE) or LTE-Advanced), and the target node 104B can be associated with a fifth generation cellular radio access technology (e.g., 5G New Radio).

[0122] At 303, the UE 100 stores a successful handover report indicating the successful inter-RAT handover of the UE 100 from the source node 104 to the target node 104B. For example, the SHR can be generated as a result of the T304 SHR percentage threshold being exceeded. The T304 SHR percentage threshold (thresholdPercentageT304) is a time threshold that can include a certain portion or ratio or percentage of a configured T304 value. For example, if the T304 value is configured to be 10 seconds, the T304 SHR percentage threshold can be set to 50% of the T304 value, i.e., 5 seconds. The T304 SHR percentage threshold can also be referred to herein as a T304 SHR portion threshold or a T304 SHR ratio threshold.

[0123] In other words, the inter-RAT handover from the source node to the target node is successful, but the UE stores the SHR as a result of the T304 SHR percentage threshold being exceeded during the inter-RAT handover.

[0124] For example, the successful handover report can be stored in an internal memory of the UE 100.

[0125] At 304, the UE 100 can send an indication to the target node 104B indicating availability of the successful handover report. For example, the indication can include a “successHO-InfoAvailable” flag sent in an RRCReconfigurationComplete message.

[0126] At 305, based on receiving the indication, the target node 104B can send a request to the UE 100 for providing the successful handover report. For example, the request can be sent in a UEInformationRequest message.

[0127] At 306, the UE 100 sends a successful handover report to the target node 104B. The UE 100 can send the successful handover report based on receiving the request from the target node 104B. For example, the successful handover report can be sent in a UEInformationResponse message. The target node 104B receives the successful handover report from the UE 100. In other words, the target node 104B can acquire the successful handover report message from the UE 100 via the UEInformationRequest and UEInformationResponse procedure.

[0128] The successful handover report can include information indicating an identity of the source cell 121 provided by the source node 104 from a LTE cell and an identity of the target cell 122 (i.e., the current NR cell) provided by the target node 104B. The successful handover report can also identify the handover as an inter-radio access technology handover (e.g., from LTE to NR).

[0129] The successful handover report further indicates that a time threshold (e.g., a T304 SHR percentage threshold) associated with monitoring of an uplink synchronization procedure between the UE 100 and the target node 104B was exceeded during the successful inter-radio access technology handover, resulting in a timing issue associated with the uplink synchronization procedure. The uplink synchronization procedure can be part of a random access procedure between the UE 100 and the target node 104B. In other words, the random access procedure between the UE 100 and the target node 104B took longer than expected.

[0130] The successful handover report can be encoded in a format associated with a fifth generation cellular radio access technology (e.g., 5G NR).

[0131] At 307, the target node 104B determines, based on the successful handover report, whether the exceeding of the time threshold was caused by an issue at the target node 104B (e.g., a random access issue such as a RACH misconfiguration).

[0132] In other words, based on the knowledge that the SHR was triggered due to T304, the target node 104B starts a root cause analysis based on the random access report included in the SHR, as indicated in the SHR. The cause can be, for example, weak radio link conditions (i.e., the handover was initiated too early at the source node 104), or a RACH misconfiguration at the target node 104B.

[0133] At 308, based on determining that the exceeding of the time threshold is not caused by a problem at the target node (i.e., based on determining that the timing problem is caused by the source node due to the premature decision of the successful inter-radio access technology handover), the target node 104B sends information to the source node 104 indicating that the timing problem associated with the uplink synchronization procedure during the successful inter-radio access technology handover is caused by the premature initiation of the successful inter-radio access technology handover by the source node 104. The source node 104 receives the information.

[0134] Thus, the information sent from the target node 104B to the source node 104 can indicate at least one timing problem associated with the uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment 100 from the source node 104 to the target node 104B.

[0135] For example, the information can be sent in a handover report message (e.g., via the XNAP interface) or in an inter-system handover report message (e.g., via the NGAP interface). The handover report message can comprise a new handover report type information element referred to as, for example, “almost early inter-RAT handover” or any other formula encoded as ENUM in the standard, which indicates that the target NR cell 122 was not stable enough, which delayed the handover and increased the interruption time during the handover. The handover report message can also indicate the identity of the source cell 121 and / or the identity of the target cell 122 (faulty cell). The handover report message can also comprise a binary flag indicating that the cause of the SHR is the T304 SHR percentage threshold being exceeded if the binary flag is set to true.

[0136] Alternatively, if the target node 104B determines that the exceeding of the time threshold is caused by a problem at the target node (e.g., RACH error configuration), the target node 104B can consider it as an event related to random access optimization in the target cell 122 for the target node 104B.

[0137] At 309, the source node 104 increments a counter based on the information received from the target node 104B.

[0138] For example, the counter can be a new counter (e.g., “almost early inter-RAT HO” counter) indicating the number of inter-radio access technology handovers associated with the timing problem related to the uplink synchronization procedure caused by the premature initiation of the successful inter-radio access technology handover by the source node 104. In this case, the source node 104 can also generate a separate counter for “early handover” (RLF-based handover) (e.g., “early inter-RAT HO” counter).

[0139] Alternatively, the counter can be a legacy counter (e.g., an "early inter-RAT HO" counter) that indicates the number of early (e.g., RLF-based early handover) inter-radio access technology handovers from the source node to the target node. In this case, the counter can be incremented in a weighted manner based on information indicating that the timing problem associated with the uplink synchronization procedure during a successful inter-radio access technology handover was caused by an early initiation of the successful inter-radio access technology handover by the source node 104 (i.e., because the handover was an "almost too early" handover). In other words, in this case, the "early" handover and the "almost too early" handover can be merged into one counter.

[0140] Incrementing the counter in a weighted manner means increasing the value of the counter in a manner that assigns different weights or importance to different increments. For example, if the counter represents "early handover" (with RLF) and "almost early handover" (without RLF), the counter can be incremented in a weighted manner to reflect the relative importance between "early handover" and "almost early handover". Early handover (with RLF) can be associated with a higher importance compared to "almost early handover" (with RLF), and thus early handover (with RLF) can result in more increments of the counter than "almost early handover" (without RLF).

[0141] For example, in the case of "almost early" handover (without RLF), the counter can be incremented by a value less than one (<1), while in the case of "early" handover (with RLF), the counter can be incremented by a value of one. As a non-limiting example, in the case of "almost early" handover (without RLF), a value of 0.5 can be added to the counter, while in the case of "early" handover (with RLF), a value of one can be added to the counter.

[0142] At 310, the source node 104 sends counter information indicating the value of the counter to a network entity, such as the network manager 111 (or the PM part of the NMS or a SON entity). The SON entity of the network management system 111 receives the counter information. The SON entity of the network management system 111 can comprise a mobility robustness optimization functionality.

[0143] For example, the counter information can be sent via the Itf-N interface at the end of a measurement period for a cell pair comprising the source cell 121 and the target cell 122.

[0144] In case the source node 104 generates separate counters for "early handover" and "almost early handover", then the source node 104 can report the values of both counters to the network manager 111 (or the SON entity) in the counter information.

[0145] At 311, the network manager 111 (or SON entity of the NMS) optimizes one or more radio measurement thresholds associated with triggering handover from the source node to the target node based at least in part on the counter information. For example, if the number of successful inter-radio access technology handovers associated with timing issues is above a threshold, then the optimization can be performed.

[0146] In other words, based on the new PM counter (i.e., the number of successful “almost too early” inter-RAT handovers associated with timing issues related to uplink synchronization), which can be part of a KPI, e.g., given as a ratio of the new PM counter to the total number of successful handovers from the source node, and possibly other rules specific to the operator, the network manager 111 (or SON entity) can initiate MRO optimization of the source cell 121 for the radio measurement threshold(s) used to trigger handover from the source cell 121 (e.g., LTE cell) to the target cell 122 (e.g., NR cell).

[0147] At 312, the network manager 111 (or CM part of the NMS) sends an indication to the source node 104 indicating the optimized one or more radio measurement thresholds. In other words, the possible change of the radio measurement threshold(s) used to trigger handover from the source cell 121 to the target cell 122 is communicated to the source node 104. Thus, there can be no new communication from the NR to the LTE side to provide this optimization.

[0148] The source node 104 can then apply the optimized one or more radio measurement thresholds to subsequent handovers from the source node 104 to the target node 104B. The optimized one or more radio measurement thresholds can help avoid or reduce timing issues associated with uplink synchronization procedures during subsequent handovers.

[0149] Figure 3 An advantage of the example embodiment is that it fits into the key aspect of the MRO philosophy, i.e., the node responsible for the tracked problem is creating and counting the MRO counter(s). Furthermore, the MRO function at the source LTE 104 can decide whether it integrates these “almost too early” handovers with the RLF-based too early handover counter in a weighted form, which would prevent the introduction of a new counter in the LTE standard. The example embodiment can also be applied to inter-system deployments, e.g., with separate OAM systems for LTE and NR. However, the example embodiment can have a slight impact on the LTE standard to enable the source LTE node 104 to decode the new handover report type information element provided in the handover report message from the target NR node 104B.

[0150] Figure 3A flow diagram illustrating example embodiments in accordance with a method performed by an apparatus 800 is shown. The apparatus 800 can be, for example, a network node such as the target node 104B or comprise or be comprised in a network node such as the target node 104B. The network node can be, for example, a gNB or ng-eNB or eNB.

[0151] Referring to Figure 4 In block 401, the apparatus receives, from a user equipment 100, a successful handover report indicating a successful inter-radio access technology handover of the user equipment 100 from a source node 104 to a target node 104B, the apparatus being associated with the target node 104B.

[0152] The successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment 100 and the target node 104B.

[0153] In block 402, the apparatus determines, based on the successful handover report, whether the exceeding of the time threshold was caused by a problem at the target node 104B. For example, the problem at the target node can refer to a RACH misconfiguration.

[0154] In block 403, based on a determination that the exceeding of the time threshold was not caused by a problem at the target node 104B (block 402: NO), the apparatus sends, to the source node 104 or to a network entity different from the source node 104 (e.g., a SON function of the network manager 111 or NMS), information indicating at least one timing problem associated with an uplink synchronization procedure of at least the successful inter-radio access technology handover (i.e., at least one successful inter-radio access technology handover).

[0155] For example, the source node 104 can be associated with a fourth generation cellular radio access technology (e.g., LTE or LTE-Advanced) and the target node 104B can be associated with a fifth generation cellular radio access technology (e.g., 5G NR), wherein the successful handover report can be encoded in a format associated with the fifth generation cellular radio access technology.

[0156] The at least one timing problem associated with the uplink synchronization procedure can be based on a premature decision of the successful inter-radio access technology handover by the source node 104.

[0157] The information sent to the source node 104 can indicate that the at least one timing problem associated with the uplink synchronization procedure during the successful inter-radio access technology handover was caused by a premature initiation of the successful inter-radio access technology handover. For example, the information can refer to the above-mentioned “almost too early inter-RAT handover” information element.

[0158] The information transmitted to the network entity 111 can comprise counter information indicating a number of successful inter-radio access technology handovers from the source node 104 to the target node 104B within a predefined time period, the number of successful inter-radio access technology handovers being associated with at least one timing issue. In other words, the counter information can indicate a number of "almost too early" handovers (i.e. no RLF, too early inter-RAT handover) counted during the predefined time period of a cell pair comprising the source cell 121 and the target cell 122.

[0159] Figure 4 A flowchart illustrating an example embodiment of a method according to the method performed by the apparatus 800 is shown. The apparatus 800 can be, for example, a network node such as the target node 104B or comprise or be comprised in a network node such as the target node 104B. The network node can be, for example, a gNB or ng-eNB or eNB.

[0160] Reference is made to Figure 5 In block 501, the apparatus receives, from the user equipment 100, a successful handover report indicating a successful inter-radio access technology handover of the user equipment 100 from the source node 104 to the target node 104B, the apparatus being associated with the target node 104B.

[0161] The successful handover report indicates that a time threshold was exceeded during the successful inter-radio access technology handover, the time threshold being associated with monitoring of an uplink synchronization procedure between the user equipment 100 and the target node 104B.

[0162] In block 502, the apparatus determines, based on the successful handover report, whether the exceeding of the time threshold was caused by an issue at the target node 104B. For example, the issue at the target node can refer to a RACH misconfiguration.

[0163] In block 503, based on a determination that the exceeding of the time threshold was not caused by an issue at the target node 104B (block 502: NO), the apparatus increments a counter indicating a number of successful inter-radio access technology handovers from the source node 104 to the target node 104B, the number of successful inter-radio access technology handovers being associated with at least one timing issue.

[0164] In block 504, the apparatus sends, to a network entity different from the source node 104 (e.g., a SON function of the network manager 111 or the NMS), counter information indicating a value of the counter, i.e., a number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, the number of successful inter-radio access technology handovers being associated with at least one timing issue. In other words, the counter information can indicate a number of “almost too early” handovers (i.e., early inter-RAT handovers without RLF) counted during the predefined time period for the cell pair comprising the source cell 121 and the target cell 122.

[0165] For example, the source node 104 can be associated with a fourth generation cellular radio access technology (e.g., LTE or LTE-Advanced), and the target node 104B can be associated with a fifth generation cellular radio access technology (e.g., 5G NR), wherein the successful handover report can be encoded in a format associated with the fifth generation cellular radio access technology.

[0166] The at least one definition issue associated with the uplink synchronization procedure can be based on a too early decision of a successful inter-radio access technology handover by the source node 104.

[0167] Figure 5 A flowchart illustrating an example embodiment of a method according to the apparatus 800 is shown. For example, the apparatus 800 can be a network node such as the source node 104 or comprise or be comprised in a network node such as the source node 104. The network node can be, for example, a gNB or ng-eNB or eNB.

[0168] With reference to Figure 6 In block 601, the apparatus receives information indicating at least one timing issue associated with an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment 100 from a source node 104 to a target node 104B, the apparatus being associated with the source node 104, wherein the information is received from the target node 104B.

[0169] The at least one timing issue associated with the uplink synchronization procedure can be based on a too early decision of a successful inter-radio access technology handover by the source node 104.

[0170] In block 602, the apparatus increments a counter based on the information.

[0171] In block 603, the apparatus sends, to a network entity (e.g., a SON function of the network manager 111 or the NMS), counter information indicating a value of the counter.

[0172] For example, the information received from the target node 104B can indicate that at least one timing problem associated with the uplink synchronization procedure was caused by an early initiation of the at least one successful inter-radio access technology handover. For example, the information received from the target node 104B can refer to the above-mentioned "almost early inter-RAT handover" information element.

[0173] The counter can indicate a number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, the number of successful inter-radio access technology handovers being associated with at least one timing problem. In other words, in this case, the counter information can at least indicate a number of "almost early" handovers (i.e. inter-RAT handovers without RLF) counted during a predefined time period of a cell pair comprising the source cell 121 and the target cell 122.

[0174] As another example, the counter can be incremented in a weighted manner based on the information received from the target node, wherein the information can indicate that at least one timing problem associated with the uplink synchronization procedure was caused by an early initiation of the at least one successful inter-radio access technology handover. In this case, the counter can indicate a number of early inter-radio access technology handovers (e.g. handovers based on RLF) from the source node to the target node.

[0175] For example, the source node 104 can be associated with a fourth generation cellular radio access technology (e.g. LTE or LTE-Advanced) and the target node 104B can be associated with a fifth generation cellular radio access technology (e.g. 5G NR), wherein the successful handover report can be encoded in a format associated with the fifth generation cellular radio access technology.

[0176] Figure 6 A flowchart illustrating an example embodiment of a method according to the method performed by the apparatus 900 is shown. For example, the apparatus 900 can be a network entity such as the network manager 111 or host an autonomic network function in a network management system or comprise or be included in a network entity such as the network manager 111 or host an autonomic network function in a network management system.

[0177] Referring to Figure 7 In block 701, the apparatus receives information indicating at least one timing problem associated with an uplink synchronization procedure of at least one successful inter-radio access technology handover of at least one user equipment 100 from a source node 104 to a target node 104B, wherein the information is received from the target node 104B (e.g. as described above with respect to the network entity 110).Figure 7 of the source node 104 (e.g., as indicated at 209) or the target node 104B (e.g., as indicated at 310) is received. Figure 2

[0178] The at least one timing issue associated with the uplink synchronization procedure can be an early decision based on at least one successful inter-radio access technology handover.

[0179] In block 702, the apparatus optimizes one or more radio measurement thresholds associated with triggering a handover from a source node to a target node based at least in part on the information.

[0180] For example, the information received from the target node 104B or the source node 104 can comprise counter information indicating a number of successful inter-radio access technology handovers from the source node 104 to the target node 104B within a predefined time period, the number of successful inter-radio access technology handovers being associated with the at least one timing issue. For example, the counter information can indicate a counter value of the above-mentioned “almost early inter-RAT HO” counter. In this case, the optimization can be based at least on the number of successful inter-radio access technology handovers associated with the at least one timing issue (e.g., the number of early inter-RAT handovers without RLF indicated by the “almost early inter-RAT HO” counter).

[0181] The optimization can also be based on a number of early and radio link failure causing inter-radio access technology handovers (e.g., the above-mentioned “early inter-RAT HO” counter) from the source node to the target node within a predefined time period, which can be reported, for example, from the source node 104.

[0182] The apparatus can send an indication to the source node 104 indicating the optimized one or more radio measurement thresholds.

[0183] The above-described blocks, related functions and information exchanges (messages) do not have an absolute chronological order, and some of them can be performed simultaneously or in a different order than described. Other functions can also be performed between or within them, and other information and / or other rules can be sent. Some blocks or parts of blocks or one or more pieces of information can also be omitted or replaced by corresponding blocks or parts of blocks or one or more pieces of information. Figure 3

[0184] ​​As used herein, “at least one of ” and “one or more of ” and similar phrases, where the list of two or more elements is connected by “and” or “or”, means at least any one of the elements, or at least any two or more of the elements.

[0185] Figure 2 to Figure 7 An example of an apparatus 800 including means for performing one or more of the example embodiments described above is shown. For example, the apparatus 800 can be an apparatus such as a network node 104 of a radio access network, network node 104B, or comprising or being included in a network node 104 of a radio access network, network node 104B.

[0186] A network node can also be referred to as, for example, a source node, a target node, a network element, a radio access network (RAN) node, a next generation radio access network (NG-RAN) node, a NodeB, an eNB, an ng-eNB, a gNB, a base transceiver station (BTS), a base station, an access node, an access point (AP), a cell site, a relay node, a repeater, an integrated access and backhaul (IAB) node, an IAB donor node, a distributed unit (DU), a central unit (CU), a baseband unit (BBU), a radio unit (RU), a radio head, a remote radio head (RRH), or a transmission and reception point (TRP).

[0187] The apparatus 800 can comprise, for example, circuitry or a chipset adapted to implement one or more of the example embodiments described above. The apparatus 800 can be an electronic device comprising one or more electronic circuits. The apparatus 800 can comprise a communication control circuitry 810, such as at least one processor, and at least one memory 820 storing instructions 822 that, when executed by the at least one processor, cause the apparatus 800 to perform one or more of the example embodiments described above. Such instructions 822 can for example comprise computer program code (software). The at least one processor and the at least one memory storing instructions can provide means for providing or causing performance of any of the methods and / or blocks described above.

[0188] The processor is coupled to the memory 820. The processor is configured to read data from and write data to the memory 820. The memory 820 can include one or more memory units. The memory units can be volatile or non-volatile. It should be noted that there can be one or more non-volatile memory units and one or more volatile memory units, or alternatively, one or more non-volatile memory units, or alternatively, one or more volatile memory units. Volatile memory can be, for example, random access memory (RAM), dynamic random access memory (DRAM), or synchronous dynamic random access memory (SDRAM). Non-volatile memory can be, for example, read only memory (ROM), programmable read only memory (PROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, optical storage, or magnetic storage. Generally, the memory can be referred to as a non-transitory computer readable medium. The term “non-transitory,” as used herein with respect to a medium, is a limitation of the medium itself (i.e., tangible, as opposed to a signal), and not a limitation on the persistence of data stored thereon (e.g., RAM vs. ROM). The memory 820 stores computer readable instructions executed by the processor. For example, the non-volatile memory stores the computer readable instructions, and the processor executes the instructions using the volatile memory for temporary storage of data and / or instructions.

[0189] The computer readable instructions can have been pre-stored to the memory 820, or alternatively or additionally, they can be received by the apparatus via an electromagnetic carrier wave signal and / or can be copied from a physical entity such as a computer program product. Execution of the computer readable instructions causes the apparatus 800 to perform one or more of the functions described above.

[0190] The memory 820 can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and / or removable memory. The memory can include a configuration database for storing configuration data, such as a list of current neighbor cells, and in some example embodiments, the structure of frames used in detected neighbor cells.

[0191] The device 800 may also include or be connected to a communication interface 830, such as a radio unit, which includes hardware and / or software for implementing a communication connection with one or more wireless communication devices according to one or more communication protocols. The communication interface 830 includes at least one transmitter (Tx) and at least one receiver (Rx) that can be integrated into or connected to the device 800. The communication interface 830 may provide components for performing some of the blocks of the above-described example embodiments. The communication interface 830 may include one or more components controlled by a corresponding control unit, such as: a power amplifier, a digital front end (DFE), an analog-to-digital converter (ADC), a digital-to-analog converter (DAC), a frequency converter, a modulator (demodulator), and / or encoder / decoder circuitry.

[0192] Communication interface 830 provides the device with radio communication capabilities for communication in a wireless communication network. The communication interface may, for example, provide a radio interface to one or more wireless communication devices. The device 80 may also include or be connected to another interface of core network 110 (such as a network coordinator device), or connected to network manager 111 or AMF, and / or other network nodes 104, 104B of the wireless communication network.

[0193] The apparatus 800 may also include a scheduler 840 configured to allocate radio resources. The scheduler 840 may be configured together with the communication control circuitry system 810, or the scheduler 840 may be configured separately.

[0194] It should be noted that device 800 may also include Figure 8 Various components are not shown. These components can be hardware components and / or software components.

[0195] Figure 8 An example of an apparatus 900 is shown, comprising components for performing one or more of the example embodiments described above. For example, the component may be a network manager 111, a self-organizing network function hosted in a network management system, or a network function virtualization infrastructure.

[0196] The apparatus 900 can comprise circuitry or a chipset adapted to implement one or more of the example embodiments described above, for example. The apparatus 900 can be an electronic device or a computing system comprising one or more electronic circuits. The apparatus 900 can comprise a control circuitry 910, such as at least one processor, and at least one memory 920 storing instructions 922 that, when executed by the at least one processor, cause the apparatus 900 to perform one or more of the example embodiments described above. Such instructions 922 can comprise computer program code (software), for example. The at least one processor and the at least one memory storing instructions can provide means for providing or causing execution of any of the methods and / or blocks described above.

[0197] The processor is coupled to the memory 920. The processor is configured to read data from and write data to the memory 920. The memory 920 can comprise one or more memory units. The memory units can be volatile or non-volatile. It should be noted that there can be one or more non-volatile memory units and one or more volatile memory units, or alternatively, one or more non-volatile memory units, or alternatively one or more volatile memory units. Volatile memory can be, for example, random access memory (RAM), dynamic random access memory (DRAM), or synchronous dynamic random access memory (SDRAM). Non-volatile memory can be, for example, read only memory (ROM), programmable read only memory (PROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), flash memory, optical storage, or magnetic storage. Generally, the memory can be referred to as a non-transitory computer readable medium. The term “non-transitory” as used herein is a limitation of the medium itself (i.e., tangible, rather than a signal) and not a limitation on the persistence of data stored thereon (e.g., RAM vs. ROM). The memory 920 stores computer-readable instructions for execution by the processor. For example, the non-volatile memory stores the computer-readable instructions and the processor executes the instructions using the volatile memory for temporary storage of data and / or instructions.

[0198] The computer-readable instructions can have been pre-stored to the memory 920, or alternatively or additionally, they can be received by the apparatus via an electromagnetic carrier signal and / or can be copied from a physical entity such as a computer program product. Execution of the computer-readable instructions causes the apparatus 900 to perform one or more of the functions described above.

[0199] The memory 920 can be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and / or removable memory.

[0200] The apparatus 900 can also include or be connected to a communication interface 930 including hardware and / or software for implementing communication connections according to one or more communication protocols. The communication interface 930 can include at least one transmitter (Tx) and at least one receiver (Rx) that can be integrated into the apparatus 900 or to which the apparatus 900 can be connected. The communication interface 930 can provide means for performing some of the blocks of one or more of the example embodiments described above. The communication interface 930 can include one or more components controlled by a respective control unit, such as power amplifiers, digital front ends (DFEs), analog-to-digital converters (ADCs), digital-to-analog converters (DACs), frequency converters, modulators (demodulators), and / or encoder / decoder circuits.

[0201] The communication interface 930 provides the apparatus with communication capabilities to communicate in a wireless communication network. The communication interface 930 can for example provide a radio, cable, or optical fiber interface to one or more network nodes 104, 104B of a radio access network.

[0202] It should be noted that the apparatus 900 can also include various components not shown in FIG. 9. The various components can be hardware components and / or software components. Figure 9 Figure 9

[0203] As used in this application, the term "circuitry" can refer to one or more or all of the following:

[0204] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application the term "circuitry" also covers an implementation that has a sole hardware circuit implementation or a sole processor or processor core implementation without software

[0205] ​The techniques and methods described herein can be implemented by various means. For example, these techniques can be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. For a hardware implementation, the apparatus(es) of an example embodiment can be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), graphics processing units (GPUs), processors, controllers, micro-controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. For firmware or software, the implementation can be carried out through modules of at least one chip set (e.g., procedures, functions, and so on) that perform the functions described herein. The software codes can be stored in memory units and executed by processors. The memory unit can be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as is known in the art. Additionally, the components of the systems described herein can be rearranged and / or complemented by additional components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and that is not limited to the precise configurations set forth in the given figure, as will be appreciated by one skilled in the art.

[0206] It will be apparent to those skilled in the art that, with the progress of technology, the present disclosure concept can be implemented in various ways. The embodiments are not limited to the above-described example embodiments, but can be varied within the scope of the claims. Therefore, all words and expressions are to be interpreted broadly and they are intended to illustrate, not to limit, the embodiments.

Claims

1. An apparatus comprising at least one processor and at least one memory, the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: The device receives a successful handover report from the user equipment, indicating a successful inter-radio access technology handover from the source node to the target node, and the device is associated with the target node. The successful handover report indicates that a time threshold was exceeded during the successful handover between the radio access technologies, and the time threshold is associated with the monitoring of the uplink synchronization process between the user equipment and the target node; Based on the successful handover report, determine whether the exceeding of the time threshold was caused by a problem at the target node; as well as Based on the determination that the exceeding of the time threshold is not caused by the problem at the target node, information indicating at least one timing problem is sent to the source node or to a network entity different from the source node, the at least one timing problem being associated with the uplink synchronization process of at least the successful handover between radio access technologies.

2. The apparatus of claim 1, wherein the source node is associated with fourth-generation cellular radio access technology and the target node is associated with fifth-generation cellular radio access technology. The successful handover report is encoded in a format associated with the fifth-generation cellular radio access technology.

3. The apparatus according to any of the preceding claims, wherein the at least one timing problem associated with the uplink synchronization process is based on a premature decision made by the source node regarding the successful inter-radio access technology handover.

4. The apparatus according to any of the preceding claims is further configured such that: Based on the determination that the exceeding of the time threshold is not caused by the problem at the target node, a counter is incremented, wherein the counter indicates the number of successful inter-radio access technology handovers from the source node to the target node, the number of successful inter-radio access technology handovers being associated with the at least one timing problem. The information is sent to the network entity, and the information includes counter information indicating the number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, the number of successful inter-radio access technology handovers being associated with the at least one timing issue.

5. The apparatus according to any one of claims 1 to 4, wherein the information is sent to the source node, the information indicating that during the successful inter-radio access technology handover, the at least one timing problem associated with the uplink synchronization process was caused by the premature initiation of the successful inter-radio access technology handover.

6. An apparatus comprising at least one processor and at least one memory, the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: The device receives information indicating at least one timing problem, the at least one timing problem being associated with an uplink synchronization process of at least one successful inter-radio access technology handover from a source node to a target node for at least one user equipment, the device being associated with the source node, wherein the information is received from the target node; Based on the information, increment the counter; as well as Send counter information indicating the value of the counter to the network entity.

7. The apparatus of claim 6, wherein the information received from the target node indicates that, during the at least one successful handover between radio access technologies, the at least one timing problem associated with the uplink synchronization process is caused by the premature initiation of the at least one successful handover between radio access technologies. The counter indicates the number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, and the number of successful inter-radio access technology handovers is associated with the at least one timing problem.

8. The apparatus of claim 6, wherein the counter is incremented in a weighted manner based on information received from the target node, the information indicating that during the at least one successful inter-radio access technology handover, the at least one timing problem associated with the uplink synchronization process was caused by the premature initiation of the at least one successful inter-radio access technology handover. The counter indicates the number of premature handovers between radio access technologies from the source node to the target node.

9. An apparatus comprising at least one processor and at least one memory, the at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: Receive information indicating at least one timing problem, said timing problem being associated with an uplink synchronization process of at least one successful inter-radio access technology handover from a source node to a target node for at least one user equipment, wherein said information is received from the target node or the source node; and Based at least in part on the information, one or more radio measurement thresholds are optimized, the one or more radio measurement thresholds being associated with triggering a handover from the source node to the target node.

10. The apparatus of claim 9, wherein the at least one timing problem associated with the uplink synchronization process is a premature decision based on the at least one successful handover between radio access technologies.

11. The apparatus according to any one of claims 9 to 10, wherein the information received from the target node or the source node includes counter information indicating the number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, the number of successful inter-radio access technology handovers being associated with the at least one timing problem. The optimization is based at least on the number of successful handovers between radio access technologies associated with the at least one timing problem.

12. The apparatus of claim 11, wherein the optimization is further based on the number of premature handovers between radio access technologies from the source node to the target node that cause radio link failures within the predefined time period.

13. The apparatus according to any one of claims 9 to 12, further comprising: Send an indication to the source node for specifying the optimized one or more radio measurement thresholds.

14. A method comprising: The device receives a successful handover report from the user equipment, indicating a successful inter-radio access technology handover from the source node to the target node, and the device is associated with the target node. The successful handover report indicates that a time threshold was exceeded during the successful handover between the radio access technologies, and the time threshold is associated with the monitoring of the uplink synchronization process between the user equipment and the target node; Based on the successful handover report, the device determines whether the exceeding of the time threshold is caused by a problem at the target node; as well as Based on the determination that the exceeding of the time threshold is not caused by the problem at the target node, the device sends information indicating at least one timing problem to the source node or to a network entity different from the source node, the at least one timing problem being associated with the uplink synchronization process of at least the successful handover between radio access technologies.

15. The method of claim 14, wherein the source node is associated with fourth-generation cellular radio access technology and the target node is associated with fifth-generation cellular radio access technology. The successful handover report is encoded in a format associated with the fifth-generation cellular radio access technology.

16. The method according to any of the preceding claims 14 to 15, wherein the at least one timing problem associated with the uplink synchronization process is based on a premature decision made by the source node regarding the successful inter-radio access technology handover.

17. The method according to any one of claims 14 to 16, further comprising: Based on the determination that the exceeding of the time threshold is not caused by the problem at the target node, a counter is incremented, wherein the counter indicates the number of successful inter-radio access technology handovers from the source node to the target node, the number of successful inter-radio access technology handovers being associated with the at least one timing problem. The information is sent to the network entity, and the information includes counter information indicating the number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, the number of successful inter-radio access technology handovers being associated with the at least one timing issue.

18. The method of any one of claims 14 to 17, wherein the information is sent to the source node, the information indicating that during the successful inter-radio access technology handover, the at least one timing problem associated with the uplink synchronization process was caused by the premature initiation of the successful inter-radio access technology handover.

19. A method comprising: The device receives information indicating at least one timing problem, which is associated with an uplink synchronization process of at least one successful inter-radio access technology handover from a source node to a target node for at least one user equipment, the device being associated with the source node, wherein the information is received from the target node; The device increments the counter based on the information; as well as The device sends counter information indicating the value of the counter to the network entity.

20. The method of claim 19, wherein the information received from the target node indicates that, during the at least one successful handover between radio access technologies, the at least one timing problem associated with the uplink synchronization process was caused by the premature initiation of the at least one successful handover between radio access technologies. The counter indicates the number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, and the number of successful inter-radio access technology handovers is associated with the at least one timing problem.

21. The method of claim 19, wherein the counter is incremented in a weighted manner based on information received from the target node, the information indicating that during the at least one successful inter-radio access technology handover, the at least one timing problem associated with the uplink synchronization process was caused by the premature initiation of the at least one successful inter-radio access technology handover. The counter indicates the number of premature handovers between radio access technologies from the source node to the target node.

22. A method comprising: Receive information indicating at least one timing problem, the at least one timing problem being associated with an uplink synchronization process of at least one successful inter-radio access technology handover from a source node to a target node for at least one user equipment, wherein the information is received from the target node or the source node; as well as Based at least in part on the information, one or more radio measurement thresholds are optimized, the one or more radio measurement thresholds being associated with triggering a handover from the source node to the target node.

23. The method of claim 22, wherein the at least one timing problem associated with the uplink synchronization process is a premature decision based on the at least one successful handover between radio access technologies.

24. The method of any one of claims 22 to 23, wherein the information received from the target node or the source node includes counter information indicating the number of successful inter-radio access technology handovers from the source node to the target node within a predefined time period, the number of successful inter-radio access technology handovers being associated with the at least one timing problem. The optimization is based at least on the number of successful handovers between radio access technologies associated with the at least one timing problem.

25. The method of claim 24, wherein the optimization is further based on the number of premature handovers between radio access technologies from the source node to the target node that cause radio link failures within the predefined time period.

26. The method according to any one of claims 22 to 25, further comprising: Send an indication to the source node for specifying the optimized one or more radio measurement thresholds.

27. A non-transitory computer-readable medium comprising program instructions that, when executed by a device, cause the device to perform at least the following operations: The device receives a successful handover report from the user equipment, indicating a successful inter-radio access technology handover from the source node to the target node, and the device is associated with the target node. The successful handover report indicates that a time threshold was exceeded during the successful handover between the radio access technologies, and the time threshold is associated with the monitoring of the uplink synchronization process between the user equipment and the target node; Based on the successful handover report, determine whether the exceeding of the time threshold was caused by a problem at the target node; as well as Based on the determination that the exceeding of the time threshold is not caused by the problem at the target node, information indicating at least one timing problem is sent to the source node or to a network entity different from the source node, the at least one timing problem being associated with the uplink synchronization process of at least the successful handover between radio access technologies.

28. A non-transitory computer-readable medium comprising program instructions that, when executed by a device, cause the device to perform at least the following operations: The device receives information indicating at least one timing problem, the at least one timing problem being associated with an uplink synchronization process of at least one successful inter-radio access technology handover from a source node to a target node for at least one user equipment, the device being associated with the source node, wherein the information is received from the target node; Based on the information, increment the counter; as well as Send counter information indicating the value of the counter to the network entity.

29. A non-transitory computer-readable medium comprising program instructions that, when executed by a device, cause the device to perform at least the following operations: Receive information indicating at least one timing problem, said timing problem being associated with an uplink synchronization process of at least one successful inter-radio access technology handover from a source node to a target node for at least one user equipment, wherein said information is received from the target node or the source node; and Based at least in part on the information, one or more radio measurement thresholds are optimized, the one or more radio measurement thresholds being associated with triggering a handover from the source node to the target node.

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