Layer 1 / layer 2 triggered mobility

Abstract

A method includes: receiving an L3 measurement report from a user equipment (UE) by a source CU; determining that a handover should be performed for the UE from a serving cell associated with a source central cell to a first target cell associated with a target CU, wherein a handover configuration for the first target cell has not yet been prepared; determining to provide an LTM handover configuration with relaxed handover requirements to a source DU associated with the serving cell for an LTM handover from the UE to a second target cell associated with the source CU; sending the LTM handover configuration for the second target cell to the source DU; and sending a handover request to the target CU associated with the first target cell to prepare a handover configuration for the UE to perform a handover to the first target cell.

Description

Technical Field

[0001] This instruction pertains to wireless communication. Background Technology

[0002] A communication system can be a facility that enables communication between two or more nodes or devices (such as fixed or mobile communication devices). Signals can be carried on wired or wireless carriers.

[0003] An example of a cellular communication system is the architecture being standardized by the 3rd Generation Partnership Project (3GPP). Recent developments in this area are often referred to as the Long Term Evolution (LTE) of Universal Mobile Telecommunications System (UMTS) radio access technology. EUTRA (Evolved UMTS Terrestrial Radio Access) is the air interface for 3GPP's LTE upgrade path for mobile networks. In LTE, base stations or access points (APs) are called Enhanced Node APs (eNBs), providing radio access within a coverage area or cell. In LTE, mobile devices or mobile stations are called User Equipment (UEs). LTE has incorporated many improvements and developments. All aspects of LTE continue to improve.

[0004] The development of 5G New Radio (NR) is part of an ongoing evolution of mobile broadband to meet the requirements of 5G, similar to the evolution of earlier 3G and 4G wireless networks. Furthermore, 5G targets emerging use cases beyond mobile broadband. The goal of 5G is to deliver significant improvements in wireless performance, which may include new levels of data rates, latency, reliability, and security. 5G NR can also be expanded to efficiently connect massive Internet of Things (IoT) networks and can provide new types of mission-critical services. For example, ultra-reliable and low-latency communication (URLLC) devices may require high reliability and very low latency. 6G and other networks are also under development. Summary of the Invention

[0005] A method may include: receiving a Layer 3 measurement report from a user equipment via a source distribution unit, the Layer 3 measurement report providing results of radio signal measurements of at least one cell; determining, based on the Layer 3 measurement report, that a handover should be performed for the user equipment from a serving cell associated with the source distribution unit to a first target cell associated with a target distribution unit, wherein a handover configuration for the handover from the user equipment to the first target cell has not yet been prepared, wherein the target distribution unit is different from the source distribution unit; determining, based on the received Layer 3 measurement report, to provide a Layer 1 / Layer 2 (L1 / L2) triggered Mobility Measure (LTM) handover configuration to the source distribution unit associated with the serving cell, the LTM handover configuration having lenient handover requirements for an LTM handover from the user equipment to a second target cell, wherein the second target cell is also associated with the source distribution unit; sending the LTM handover configuration for the second target cell to the source distribution unit; and sending a handover request to the target distribution unit associated with the first target cell to prepare a handover configuration for the user equipment to perform a handover to the first target cell.

[0006] An apparatus may include: components for receiving a Layer 3 measurement report from a user equipment via a source distribution unit, the Layer 3 measurement report providing results of radio signal measurements of at least one cell; components for determining, based on the Layer 3 measurement report, that a handover should be performed by the source concentration unit for the user equipment from a serving cell associated with the source concentration unit to a first target cell associated with a target concentration unit, wherein a handover configuration for the handover from the user equipment to the first target cell has not yet been prepared, wherein the target concentration unit is different from the source concentration unit; components for determining, based on the received Layer 3 measurement report, a Layer 1 / Layer 2 triggered Mobility Measure (LTM) handover configuration to the source distribution unit associated with the serving cell, the LTM handover configuration having relaxed handover requirements for an LTM handover from the user equipment to a second target cell, wherein the second target cell is also associated with the source concentration unit; components for transmitting the LTM handover configuration for the second target cell from the source concentration unit to the source distribution unit; and components for transmitting a handover request from the source concentration unit to the target concentration unit associated with the first target cell to prepare a handover configuration for the user equipment to perform a handover to the first target cell.

[0007] An apparatus may include at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured, together with the at least one processor, to cause the apparatus to at least: receive a Layer 3 measurement report from a user equipment via a source centralization unit, the Layer 3 measurement report providing results of radio signal measurements of at least one cell; and determine, based on the Layer 3 measurement report, that a handover should be performed for the user equipment from a serving cell associated with the source centralization unit to a first target cell associated with a target centralization unit, wherein a handover configuration for the handover from the user equipment to the first target cell has not yet been prepared. The target centralized unit is different from the source centralized unit; the source centralized unit determines, based on the received Layer 3 measurement report, a Layer 1 / Layer 2 triggered mobility (LTM) LTM handover configuration to be provided to the source distribution unit associated with the serving cell. This LTM handover configuration has relaxed handover requirements for LTM handover from user equipment to a second target cell, which is also associated with the source centralized unit; the source centralized unit sends the LTM handover configuration for the second target cell to the source distribution unit; and the source centralized unit sends a handover request to the target centralized unit associated with the first target cell to prepare the handover configuration for user equipment to perform a handover to the first target cell.

[0008] A method may include: receiving, from a source central unit, a layer 1 / layer 2 triggered mobility (LTM) LTM handover configuration and a timer value, by a source distribution unit associated with the serving cell, a layer 1 / layer 2 triggered LTM handover configuration having lenient handover requirements for LTM handover from a user equipment to a target cell, the timer value being used for an effectiveness timer of the LTM handover configuration, wherein the target cell is associated with both the source central unit and a different distribution unit; starting an effectiveness timer for the LTM handover configuration by the source central unit, the effectiveness timer indicating a validity period for the LTM handover configuration; receiving a layer 1 measurement report from the user equipment before the expiration of the effectiveness timer for the LTM handover configuration by the source distribution unit; determining, based on the layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met by the source distribution unit; and sending a media access control (MAC) control element to the user equipment to trigger the user equipment to perform an LTM handover to the target cell.

[0009] An apparatus may include: components for receiving, from a source central unit, a Layer 1 / Layer 2 triggered Mobility (LTM) handover configuration and a timer value by a source distribution unit associated with a serving cell, the LTM handover configuration having lenient handover requirements for LTM handover from a user equipment to a target cell, the timer value being used for an effectiveness timer in the LTM handover configuration, wherein the target cell is associated with both the source central unit and a different distribution unit; components for initiating an effectiveness timer for the LTM handover configuration by the source central unit, the effectiveness timer indicating a validity period for the LTM handover configuration; components for receiving a Layer 1 measurement report from the user equipment by the source distribution unit before the expiration of the effectiveness timer for the LTM handover configuration; components for determining, based on the Layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met by the source distribution unit; and components for sending a Media Access Control (MAC) control element to the user equipment by the source distribution unit to trigger the user equipment to perform an LTM handover to the target cell.

[0010] An apparatus may include: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured, together with the at least one processor, to cause the apparatus to at least: receive, from a source central unit a Layer 1 / Layer 2 triggered Mobility (LTM) LTM handover configuration and a timer value, by a source distribution unit associated with a serving cell, a Layer 1 / Layer 2 triggered LTM handover configuration having lenient handover requirements for LTM handover to a target cell, the timer value being used for an effectiveness timer of the LTM handover configuration, wherein the target cell is associated with both the source central unit and a different distribution unit; initiate an effectiveness timer for the LTM handover configuration by the source central unit, the effectiveness timer indicating an effectiveness period for the LTM handover configuration; receive a Layer 1 measurement report from the user equipment by the source distribution unit before the effectiveness timer for the LTM handover configuration expires; determine, based on the Layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met by the source distribution unit; and send a Media Access Control (MAC) control element (MAC CE) to the user equipment to trigger the user equipment to perform an LTM handover to the target cell.

[0011] Other example embodiments are provided or described for each example method, including: components for performing any example method; a non-transient computer-readable storage medium including instructions stored thereon, which, when executed by at least one processor, are configured to cause a computing system to perform any example method; and an apparatus including at least one processor and at least one memory, the at least one memory including computer program code, the at least one memory and the computer program code being configured together with the at least one processor to cause the apparatus to at least perform any example method.

[0012] Details of one or more exemplary embodiments are set forth in the accompanying drawings and the following description. Other features will be apparent from the description, the drawings, and the claims. Attached Figure Description

[0013] Figure 1 This is a block diagram of a wireless network.

[0014] Figure 2 This is a diagram illustrating the movement of a UE within a wireless network, based on an example embodiment.

[0015] Figure 3 This is a flowchart illustrating the operation of the source collection unit according to the example embodiment.

[0016] Figure 4 This is a flowchart illustrating the operation of the source distribution unit according to an example embodiment.

[0017] Figures 5A to 5C This is a diagram illustrating network operations based on an example embodiment.

[0018] Figures 6A to 6C This is a diagram illustrating network operation according to another example embodiment.

[0019] Figures 7A to 7C This is a diagram illustrating network operation according to another example embodiment.

[0020] Figures 8A to 8D The illustration shows a network operation according to yet another example embodiment.

[0021] Figure 9 It is a block diagram of a wireless station or node (e.g., a network node (such as a gNB), a user node or UE, a relay node or other node). Detailed Implementation

[0022] Figure 1 This is a block diagram of wireless network 130. Figure 1In the wireless network 130, user equipment 131, 132, 133, and 135 (also referred to as mobile stations (MS) or user equipment (UE)) can connect to (and communicate with) base station (BS) 134, which can also be referred to as access point (AP), enhanced node B (eNB), gNB, or network node. The terms user equipment and UE are used interchangeably. BS may also include or be referred to as RAN (Radio Access Network) nodes, and may include a portion of the BS or a portion of the RAN node, such as a centralized unit (CU) and / or distributed unit (DU) in the case of a split BS or a split gNB. At least a portion of the functionality of the BS (e.g., access point (AP), base station (BS), or (e) node B (eNB), gNB, RAN node) can also be performed by any node, server, or host operatively coupled to a transceiver, such as a remote radio head. BS (or AP) 134 provides radio coverage within cell 136, including providing radio coverage to user equipment (or UE) 131, 132, 133, and 135. Although only four user equipment (or UE) connections or attachments to BS 134 are shown, any number of user equipment can be provided. BS 134 is also connected to core network 150 via S1 interface 151. This is just a simple example of a wireless network; other wireless networks can also be used.

[0023] A base station (e.g., such as BS 134) is an example of a radio access network (RAN) node within a wireless network. A BS (or RAN node) can be or may include (or may be alternatively referred to as) such as an access point (AP), gNB, eNB, or a portion thereof (such as a central unit (CU) and / or a distributed unit (DU) in the case of a split BS or a split gNB) or other network node.

[0024] Some functions of a communication network can be performed, at least in part, in a centralized / central unit (CU, e.g., a server, host, or node) operatively coupled to a distributed unit (DU), e.g., a radio headend / node. Therefore, a 5G network architecture can be based on so-called CU-DU separation. A gNB-CU (central node) can control multiple spatially separated gNB-DUs, each acting at least as a transmit / receive (Tx / Rx) node. However, in some embodiments, a gNB-DU (also referred to as a DU) may include, for example, the Radio Link Control (RLC), Medium Access Control (MAC) layer, and Physical (PHY) layer, while a gNB-CU (also referred to as a CU) may include layers above the RLC layer, such as the Packet Data Convergence Protocol (PDCP) layer, Radio Resource Control (RRC), and Internet Protocol (IP) layer. Other functional separations are also possible.

[0025] According to illustrative examples, a BS node (e.g., BS, eNB, gNB, CU / DU, ...) or radio access network (RAN) can be part of a mobile telecommunications system. The RAN (radio access network) can include one or more BS or RAN nodes that implement radio access technologies, such as allowing one or more UEs to access the network or core network. Therefore, for example, the RAN (RAN node, such as BS or gNB) can be located between one or more user equipments or UEs and the core network. According to example embodiments, each RAN node (e.g., BS, eNB, gNB, CU / DU, ...) or BS can provide one or more wireless communication services for one or more UEs or user equipments, such as allowing UEs to wirelessly access the network via the RAN node. Each RAN node or BS can perform or provide wireless communication services, such as allowing a UE or user equipment to establish a wireless connection to the RAN node, and sending data to one or more UEs and / or receiving data from one or more UEs. For example, after establishing a connection to a UE, the RAN node or network node (e.g., BS, eNB, gNB, CU / DU, ...) can forward data received from the network or core network to the UE, and / or forward data received from the UE to the network or core network. RAN nodes or network nodes (e.g., BS, eNB, gNB, CU / DU, ...) can perform a wide variety of other radio functions or services, such as broadcasting control information (e.g., system information or on-demand system information) to UEs, paging UEs when data is to be delivered to them, assisting UEs in handover between cells, scheduling resources for uplink data transmission from UEs and downlink data transmission to UEs, sending control information to configure one or more UEs, etc. These are just a few examples of one or more functions that a RAN node or BS can perform.

[0026] User equipment or user node (user terminal, user equipment (UE), mobile terminal, handheld wireless device, etc.) can refer to portable computing devices that operate with or without a Subscriber Identity Module (SIM), including but not limited to the following types of devices: mobile station (MS), mobile phone, cellular phone, smartphone, personal digital assistant (PDA), handheld device, device using a wireless modem (alarm or measuring device, etc.), laptop and / or touchscreen computer, tablet computer, tablet phone, game console, laptop, vehicle, sensor and multimedia device as examples, or any other wireless device. It should be understood that user equipment can also be (or may include) a nearly dedicated uplink-only device, an example of which is a camera or camcorder that loads image or video clips onto the network. Furthermore, user node can include user equipment (UE), user equipment, user terminal, mobile terminal, mobile station, mobile node, subscriber equipment, subscriber node, subscriber terminal, or other user node. For example, a user node can be used to wirelessly communicate with one or more network nodes (e.g., gNB, eNB, BS, AP, CU, DU, CU / DU) and / or with one or more other user nodes, regardless of the technology or radio access technology (RAT). In LTE (as an illustrative example), the core network 150 can be referred to as the evolved packet core (EPC), which may include a mobility management entity (MME) that can handle or assist user equipment mobility / handover between BSs, one or more gateways that can forward data and control signals between the BS and a packet data network or the Internet, and other control functions or blocks. Other types of wireless networks, such as 5G (which may be referred to as New Radio (NR)), may also include a core network.

[0027] Furthermore, the technologies described in this paper can be applied to various types of user equipment or data service types, or to user equipment that may be running multiple applications with different data service types. New 5G (NR) development can support a variety of applications or data service types, such as: Machine-Type Communication (MTC), Enhanced Machine-Type Communication (eMTC), Internet of Things (IoT) and / or Narrowband IoT user equipment, Enhanced Mobile Broadband (eMBB), and Ultra-Reliable Low-Latency Communication (URLLC). Many of these new 5G (NR) related applications may require higher performance than previous wireless networks typically offer.

[0028] The Internet of Things (IoT) can refer to a growing group of objects that may have internet or network connectivity, enabling them to send and receive information to and from other network devices. For example, many sensor-type applications or devices can monitor physical conditions or states and send reports to servers or other network devices, for example, when an event occurs. Machine-type communication (MTC, or machine-to-machine communication) can be characterized, for example, as the fully automated generation, exchange, processing, and execution of data between intelligent machines, with or without human intervention. Enhanced Mobile Broadband (eMBB) can support much higher data rates than currently available in LTE.

[0029] Ultra-Reliable Low-Latency Communication (URLLC) is a new type of data service, or a new use case, that can be supported by new radio (5G) systems. This enables emerging new applications and services, such as industrial automation, autonomous driving, vehicle safety, and eHealth services. 3GPP aims to provide connectivity with reliability corresponding to a block error rate (BLER) of 10 to 5 and U-plane (user / data plane) latency of up to 1 ms, as an illustrative example. Therefore, for example, URLLC user equipment / UEs may require significantly lower block error rates and low latency (with or without the requirement for high reliability) than other types of user equipment / UEs. Thus, for example, a URLLC UE (or a URLLC application on a UE) may require much shorter latency than an eMBB UE (or an eMBB application running on a UE).

[0030] The techniques described herein can be applied to a variety of wireless technologies or wireless networks, such as 5G (New Radio (NR)), cmWave and / or mmWave band networks, IoT, MTC, eMTC, eMBB, URLLC, 6G, and any other wireless network or wireless technology. These example networks, technologies, or data service types are provided as illustrative examples only.

[0031] User equipment (UE) can measure various signals and send one or more measurement reports to the network. For example, a UE can measure reference signals received from one or more network nodes (e.g., gNB or DU), including Channel State Information-Reference Signal (CSI-RS) and / or Synchronization Signal Block (SSB) reference signals, demodulation reference signals, and / or other reference signals. Based on the received reference signals, the UE can measure various signal parameters, such as Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal-to-Interference-plus-Noise Ratio (SINR), Received Signal Strength Indicator (RSSI), or other signal parameters.

[0032] The PHY (Physical) layer can refer to Layer 1 (L1), and the MAC (Media Access Control) layer can refer to Layer 2 (L2). RSRP, RSRQ, SINR, and RSSI are semaphores measured at L1. The UE can send L1 measurement reports (e.g., CSI-RS reports, which measure one or more signal parameters of one or more cells), source DUs, or serving cells to the gNB. These L1 measurement reports can be sent periodically, e.g., or non-periodically. L1 / L2 measurement reports may not include averaging or filtering of the measurements, or may include less averaging or filtering than L3 measurement reports. L1 (or L1 / L2) measurement reports can be sent by the UE to the serving network node or source DU, and can cause the network node to trigger or initiate an L1 / L2 triggered mobility (LTM) handover of the UE to another cell. L1 measurements (e.g., RSRP, RSRQ, RSSI) can be periodically provided or reported to the DU (MAC / PHY).

[0033] L3 measurement reports are event-based measurement reports, triggered for example, when a cell (e.g., a neighboring cell) has RSRP or RSSI (or other signal parameters) that meet certain HO (handover) event criteria. For instance, the UE can send an L3 measurement report to the serving cell or network node if, for example, the serving cell's measurement signal becomes / below a threshold, the neighboring cell's signal measurement is or becomes better than a first threshold, and / or the serving cell's signal measurement becomes worse than the neighboring cell's signal measurement than an offset threshold. Therefore, L3 measurement reports can be event-triggered measurement reports.

[0034] Compared to L1 measurement reports, L3 measurement reports may include or be based on averaging and / or filtering of more signal samples, or averaging over a longer time period. Furthermore, L3 measurement reports are sent to the CU and are event-triggered measurement reports, capable of triggering a network node to initiate or triggering a handover of the UE to another cell (e.g., L3 handover, which can be a basic handover or a conditional handover). L3 handover (L3 HO) may be based on the L3 measurement report. In response to receiving an L3 measurement report from the UE, the source network node (e.g., gNB, or source CU) may send a handover request to the target network node (e.g., the target CU). The source network node may send an RRC reconfiguration message to the UE including an HO command to cause the UE to perform a handover to the target cell, or CHO configuration (to configure the conditional handover conditions that will trigger or cause the UE to initiate a CHO to the target cell). Because L3 HO (HO or CHO) is based on L3 measurement reports, which may require more time to acquire or measure compared to L1 measurement reports (e.g., based on more signal measurement samples and / or filtering and / or averaging of those samples), L3 measurement reports may not be sent by the UE until long after the radio conditions with the serving cell / serving network node have deteriorated. If a handover configuration for the HO / CHO to the target cell has not yet been prepared, the source network node may need to send a message to the target node to request and prepare the UE's HO configuration, which can result in significant delays, such as 100 ms or more, before the UE can perform the L3 HO or CHO to the target cell. This significant delay can increase the likelihood that the UE will suffer from radio link failure (RLF) or connection loss.

[0035] In 3GPP Release 18, a new type of inter-cell mobility was introduced called L1 / L2-based inter-cell mobility (L1 / L2-triggered mobility, LTM). When a UE changes its location within the network, its radio link to the serving cell may experience significant fluctuations or degradation. To ensure radio connectivity, the network can trigger a cell change or handover. In conventional procedures (e.g., L3 HO or CHO, as described above), cell handover or HO is triggered by the network based on measurements reported from the UE (e.g., as in a triggered L3 HO), or by the UE when a specific set of conditions (assessed locally by the UE) provided by the network as a CHO configuration are met (e.g., in a CHO). In either case, the HO decision is based on L3 measurements, which can introduce significant delays or latency before the UE can execute an L3 HO or CHO.

[0036] In LTM, the source CU can receive L3 measurement reports via the source DU, and based on this, can prepare one or more HO configurations for UE handover. The source CU can send an RRC reconfiguration message to the UE (via the source DU serving the UE) to provide measurement configurations to configure the UE to perform L1 measurements of the cell, as well as configurations (or handover configurations) for one or more prepared cells. The HO configuration for each prepared cell may include, for example, beam information and bandwidth of the target cell, access information such as the random access preamble information of the target cell, and / or other configuration information for UE communication with the target cell. The UE can then measure a group of cells (e.g., the UE can measure the RSRP or RSRQ of reference signals received from this group of cells) and can periodically send L1 measurement reports to the source DU serving the UE. Based on these L1 measurement reports from the UE, the source DU associated with the UE's source CU can change the UE's serving cell via a cell handover command by sending a MAC control element (MACCE) to the UE, which instructs the gNB or CU to provide the LTM candidate (target) cell configuration previously prepared and provided to the UE via RRC signaling. Therefore, the MAC CE used for LTM HO can identify one of the eight (or other number) previously configured LTM target cell configurations that the UE should use for LTM handover. The UE can then perform a random access procedure to establish a connection with the indicated target cell.

[0037] Therefore, cell handover for LTM HO is triggered by the network node selecting an LTM candidate cell configuration (e.g., based on the strongest RSRP, RSRQ, or other signaling parameters in the received L1 measurement report) as the target configuration and informing the UE of the target cell or its HO configuration via MAC CE. LTM candidate cell configurations can typically only be added, modified, and / or released by the network via RRC signaling (RRC messages), which introduces significant latency. The LTM procedure can be used to reduce mobility (or HO) latency because LTM HO is triggered by L1 measurement reports (which have lower latency than L3 measurement reports).

[0038] Note that, for example, LTM supports intra-CU mobility, including moving to a target cell that is not the current serving cell (but the target cell is associated with or provided by the same CU as the serving cell (the one currently serving the UE), as described below). As mentioned above, unlike existing L3 HO or CHO handover procedures, in the LTM process, cell change triggering occurs via a MAC CE command sent from the source DU to the UE (based on reported L1 measurements). Although the triggering of this process is in the DU, the LTM setup (or requesting and obtaining the LTM HO configuration for the target cell) HO / cell handover is performed by the CU and sent to the UE via an RRC reconfiguration message. The sent RRC reconfiguration message contains information about all cells for which LTM has been configured for the UE.

[0039] Figure 2 This diagram illustrates a UE moving within a wireless network according to an example embodiment. In this example, the UE is configured to perform LTM handovers to cells 1, 2, and 3, which are associated with (e.g., controlled or provided by) a source CU 210. Therefore, cells 1, 2, and 3 are provided by the same CU. LTM in NR rel. 18 is defined only for intra-CU mobility, where the UE's LTM mobility can only be performed between cells within the same CU (not between cells of different CUs). Therefore, because LTM cannot be used for the UE to perform a HO to a cell of a different CU (or associated with, or controlled by) it, the UE must use an L3 HO or CHO to perform a handover to a cell controlled or associated with a CU different from its current or source CU, which may take longer to complete an L3 handover or CHO compared to an already prepared LTM handover.

[0040] Therefore, as Figure 2 As shown, when the UE moves between cells 1, 2, and 3 (example path of the UE is shown by dashed line 206), the UE can perform LTM mobility (e.g., LTM cell change or HO can be performed for the UE in any cell of source CU 210, e.g., from cell 1 to cell 2, cell 2 to cell 1, cell 2 to cell 3, or cell 3 to cell 2, ...), for example, triggered (not shown) by the source DU serving the UE (and associated with source CU 210) based on the L1 measurement report received from the UE, since all cells 1, 2, and 3 are provided by or associated with source CU 210.

[0041] refer to Figure 2At point 208, the UE (as shown in example UE path 206) is at the intersection of cells 2, 3, and 4. At point 208, the UE is connected to cell 3 (the current source cell, associated with source CU 210), but is moving towards or traveling deeper into cell 4, away from cells 3 and 2 (and into the overlapping area of ​​cells 2 and 4). Based on the UE's movement deeper into cell 4 along example path 206, an L3 measurement report can be triggered and sent by the UE, for example, based on the RSRP or RSRQ of cell 4 (for satisfying a handover event, for example, the RSRP of cell 4 is better than the RSRP of the current / serving cell 3 by a threshold). Note that cell 4 is associated with (or controlled by) the target CU 220, while the currently serving cell 3 is associated with (or controlled by) the source CU 210. Therefore, an LTM HO from cell 3 to cell 4 cannot be performed because cells 3 and 4 are associated with different CUs. Instead, based on the L3 measurement report, source CU 210 can trigger an L3 HO or CHO from cell 3 to cell 4. For the UE to execute a HO / CHO in cell 4, a new cell needs to be prepared and a handover command (which may include a CHO configuration) needs to be sent to the UE. This process takes time, potentially 100 ms or more. During this period, radio conditions between the UE and the serving cell may continue to deteriorate, and the UE may eventually experience a radio link failure (RLF) or connection loss, for example, due to deterioration of radio conditions in the current serving cell (e.g., cell 3) or the loss of a handover command, even if the UE already has one or more LTM HO configurations (e.g., for cells 1, 2, 3, ...) that would allow the UE to maintain connectivity.

[0042] For example, in Figure 2 In the example shown, when the UE moves deeper into cell 4 at point 208, the UE already has LTM HO configurations for cells 1, 2, and 3. Furthermore, based on the UE's path / movement into the overlapping area of ​​cells 2 and 4, in this example, the UE can perform a temporary LTM HO to cell 2 (as an intermediate HO step) to reduce the possibility of radio link failure, and then eventually perform an L3 HO or CHO to the preferred (stronger) cell 4. For example, performing an LTM HO to cell 2 as an intermediate or emergency HO step can avoid RLF and provide additional time to prepare the HO configuration for the L3 HO or CHO to cell 4.

[0043] Therefore, for example, while an LTM HO from cell 3 to cell 2 is not an ideal or preferred HO or cell change (a direct HO from cell 3 to cell 4 would be preferred because cell 4 provides a stronger RSRP than cell 2), a temporary or intermediate HO from cell 3 to cell 2 (e.g., where cell 2 is a better cell for the UE than cell 3) can be an emergency HO for the network, based on deteriorating radio conditions of the radio link between the UE and cell 3, for example, to avoid RLF. Such an emergency HO can be an intermediate or temporary HO performed for the UE to temporarily change the UE to a better cell than the current serving cell (if available), for example, to reduce the risk of RLF. For example, such an emergency HO or intermediate HO can be performed if radio signal measurements in an L3 measurement report received by the source CU from the UE indicate that the UE is under radio conditions below a predetermined threshold relative to the serving cell (e.g., the RSRP of the reference signal from the serving cell is less than the threshold, indicating a significant risk of RLF). As described, because the LTM HO configuration to that better cell (e.g., Figure 2 Cell 2 (which is superior to the currently serving cell 3) has already been provided to the UE, and because this HO is based on L1 measurement reports, this emergency or intermediate HO (e.g., executed as an LTM HO) can be advantageously executed very quickly compared to an L3 HO or a CHO, thus potentially avoiding RLF, or at least reducing the risk of RLF. Furthermore, at least in some cases, by executing this LTM HO (e.g., an emergency HO or an intermediate HO) to a better cell (e.g., cell 2) associated with the source CU 210, this can provide additional time (while maintaining RLF and UE connectivity) to prepare the HO command and / or CHO configuration for the L3 HO to the preferred cell 4.

[0044] like Figure 2 As described in the example, the L3 measurement report provided by the UE can provide L3 cell measurements indicating the UE's preferred HO (House of Interest) to cell 4 associated with (e.g., controlled by) the target CU 220, which differs from the UE's current CU 210. However, in this example, based on the L1 measurement report from the UE, the LTM HO has not yet been triggered at the source DU because although cell 2 is better than cell 3 (with a stronger RSRP), the RSRP of cell 2 (measured by the UE) may not be strong enough to be stronger than the RSRP of cell 3. In this case, based on the L1 measurement report, the LTM HO from cell 3 to cell 2 will not be triggered at the source DU. According to the example embodiment, in order to facilitate the UE to a better cell (e.g., Figure 2 For cell 2), the source CU 210 may provide the source DU with an LTM HO configuration that relaxes (or reduces) the HO requirements for the UE, as described in more detail below.

[0045] Therefore, according to the example embodiment, source CU 210 can: 1) receive an L3 measurement report from the UE, and based on the L3 measurement report, source CU 210 determines that a HO / CHO should be performed for the UE to cell 4 (because cell 4 meets the HO event criteria, e.g., the RSRP of cell 4 is better than the RSRP of the current serving cell 3 by more than a threshold), and source CU 210 also knows or has determined that cell 4 is not associated with source CU 210, but with target CU 220 (therefore, the UE's LTM HO is unlikely to be to cell 4); and 2) source CU 210 can determine based on the L3 measurement report that the current radio condition (e.g., RSRP or RSRQ) 3 of the radio link between the UE and the current serving cell is less than a threshold (e.g., indicating a significant or enhanced RLF risk for the UE), therefore, source CU 210 should adjust the source CU LTM HO behavior by configuring the UE's emergency LTM HO with a relaxed (or reduced) LTM HO requirement, which encourages or makes it more likely that the UE will perform a handover to the source CU 220. 210 associated cell (e.g., cell 2 or cell 1) (to a cell associated with the same CU as the serving cell), or to a cell where the UE already has an LTM HO configuration.

[0046] The source CU 210 can then send an (e.g., updated) LTM HO configuration for the UE to the source DU associated with the serving cell, wherein the (e.g., updated) LTM HO configuration includes a relaxed HO requirement for the UE to the LTM HO of the cell associated with the source CU 210. The relaxed HO requirement makes the source DU (serving the UE and associated with the source CU 210) more likely to trigger an LTM HO to one of the cells already configured for an LTM HO (e.g., cell 1 or cell 2) and / or to the cell associated with the source CU (the same CU associated with the serving cell, cell 3). The source DU will then evaluate any L1 measurement reports received from the UE, and if the relaxed HO requirement is met for that cell, it will trigger a UE LTM HO to the cell (e.g., cell 2).

[0047] In further operations, this can be performed substantially (or partially) in parallel with the LTM HO configuration / update operation described above. The source CU210 can send a handover request to the target CU 220 associated with the target cell (e.g., cell 4) to prepare the UE for an L3 handover configuration (HO or CHO) to the (more preferred) target cell (e.g., cell 4). In this example, even if the signal measurement of cell 4 (the target cell) is stronger than that of cell 2 (therefore, cell 4 associated with the target CU 220 is the more preferred target cell), the LTM HO from cell 3 to cell 2 can still be performed (if the L1 measurement of cell 2 and / or cell 3 is sufficient or meets the relaxed HO requirements to cell 2) as an intermediate HO step for the UE, for example, to reduce the likelihood of the UE experiencing an RLF. In cases where a UE performs an LTM HO from its current serving cell (e.g., cell 3) to another cell (e.g., cell 2) associated with source CU 210, this can provide (or buy) additional time (e.g., in the absence of an RLF) to prepare an L3 HO or CHO configuration for the UE, which is then provided to the UE to allow the successful execution of the L3 HO or CHO to the target cell (e.g., cell 4), thereby making an RLF or disconnection of the UE less likely.

[0048] In addition, the source CU and / or source DU can use a validity timer to indicate the validity period (including relaxed HO requirements) 210 of the LTM HO configuration (e.g., updated) sent by the source CU to the source DU. The validity period is the time during which the (e.g., updated) LTM HO configuration with relaxed HO requirements is valid. As long as the validity timer has not expired, the source DU will use the received (e.g., updated) LTM HO configuration with relaxed HO requirements to determine whether to trigger an LTM HO to the cell via MAC CE. Once the validity timer expires, the source DU will no longer use the received (e.g., updated) LTM HO configuration with relaxed HO requirements, but will revert to using the previous, default, or non-relaxed LTM HO configuration to determine whether an LTM HO should be performed based on L1 measurements from the UE. The source CU 210 can provide the source DU with both the LTM HO configuration with relaxed HO requirements and the timer value of the validity timer.

[0049] As described, the source CU 210 providing an LTM HO configuration with lenient HO requirements to the source DU (e.g., it may have a lower RSRP threshold for LTM HO to the cell) makes it more likely that an LTM HO will be performed for the UE. This (providing an LTM HO configuration with lenient HO requirements to the source DU) can be advantageously performed or provided by the source CU 210 in response to the source CU 210 determining, for example, based on an L3 measurement report from the UE, that the current radio conditions (e.g., RSRP or RSRQ) of the radio link between the UE and the current serving cell 3 are less than a threshold (e.g., the radio conditions indicate a significant or enhanced RLF risk), and therefore, an emergency or intermediate LTM HO should be configured based on the lenient HO requirements to the cell associated with the source CU to encourage or make it more likely that a temporary or intermediate HO will be performed for the UE to the cell associated with the source CU 210 before the UE performs an L3 HO or CHO to the (e.g., more preferred) target cell (e.g., cell 4) associated with the target CU 220. Additional features, operations, and / or examples are described herein. The descriptions and figures provided herein, including the figures and descriptions below, provide further details, descriptions and / or illustrative examples.

[0050] Figure 3 This is an example embodiment of a flowchart illustrating the operation of a source set unit. Operation 310 includes operations performed by a source set unit (e.g., source CU210, ...). Figure 2 The system receives a Layer 3 (L3) measurement report from a user equipment (e.g., UE) via a source distribution unit (source DU). The Layer 3 measurement report provides the results of radio signal measurements for at least one cell. Operation 320 includes the use of a source centralization unit (e.g., source CU 210). Figure 2 Based on the Layer 3 measurement report, it is determined that a handover should be performed for the UE from the serving cell associated with the source central unit (e.g., source CU 210) to the first target cell (e.g., a handover should be performed for the UE to target cell 4), the first target cell being associated with the target central unit (e.g., target cell 4 being associated with target CU 220). Figure 2 The handover configuration for the UE to the first target cell is not yet ready (e.g., the HO configuration for the L3 HO or CHO for the UE to target cell 4 is not yet ready), and the target distribution unit is different from the source distribution unit (e.g., target CU220 is different from source CU210). Operation 330 includes, as determined by the source distribution unit (e.g., source CU210) based on the received Layer 3 measurement report, sending data to the source distribution unit (e.g., source DU) associated with the serving cell (the source DU associated with serving cell 3). Figure 2The system provides a Layer 1 / Layer 2 triggered Mobility (LTM) LTM handover configuration (e.g., target cell 2) with relaxed handover requirements for LTM handover from user equipment to a second target cell, wherein the second target cell is also associated with a source centralizing unit (e.g., target cell 2 is also associated with source CU 210). Operation 340 includes sending the LTM handover configuration (LTM HO configuration for target cell 2) for the second target cell from the source centralizing unit (e.g., source CU 210) to the source distribution unit (source DU). Furthermore, operation 350 includes sending the LTM handover configuration (LTM HO configuration for target cell 2) for the second target cell from the source centralizing unit (source CU 210). Figure 2 The system sends a handover request to the target central unit (target CU220) associated with the first target cell (target cell 4 is associated with target CU220) to prepare the handover configuration for the user equipment to perform a handover to the first target cell.

[0051] about Figure 3 The method may further include initiating an validity timer for LTM handover configuration by a source central unit, the validity timer indicating the validity period of the LTM handover configuration.

[0052] about Figure 3 The method may further include, when making a determination to provide LTM handover configuration to the source distribution unit, the source central unit starting an validity timer for the LTM handover configuration.

[0053] about Figure 3 The method may further include a handover of the user equipment to the first target cell performed after either: 1) the expiration of an validity timer, or 2) an LTM handover of the user equipment to the second target cell based on an LTM handover configuration for the second target cell.

[0054] about Figure 3 The method may further include receiving an LTM handover indication from the source centralization unit, indicating that an LTM handover to a second target cell has been triggered; stopping a validity timer for LTM handover configuration based on the receipt of the LTM handover indication; and sending a radio resource control (RRC) message including a handover command or conditional handover configuration from the source centralization unit to the source distribution unit associated with the second target cell, to instruct the user equipment to perform a handover or conditional handover to a first target cell associated with the target centralization unit.

[0055] about Figure 3The method may include detecting the expiration of a validity timer for an LTM handover configuration before an LTM handover indication indicating that an LTM handover to a second target cell has been triggered; and sending a radio resource control (RRC) message, including a handover command or conditional handover configuration, from a source centralization unit to a source distribution unit associated with the second target cell to instruct the user equipment to perform a handover or conditional handover to a first target cell associated with the target centralization unit.

[0056] about Figure 3 The method may further include an RRC message including an incremental configuration, the incremental configuration including one or more updated parameters for handover of the user equipment to the first target cell, the one or more updated parameters referencing a complete configuration known to the user equipment, wherein the complete configuration corresponds to the configuration of the serving cell.

[0057] about Figure 3 The method allows the RRC message to include incremental configuration, which includes one or more updated parameters for handover of the user equipment to the first target cell, the one or more updated parameters referencing the complete configuration known to the user equipment, wherein the complete configuration corresponds to the configuration of the second target cell.

[0058] about Figure 3 The method involves the user equipment using incremental configuration for handover to the first target cell after performing a handover from the serving cell to the second target cell.

[0059] about Figure 3 The LTM handover configuration may include one or more of the following values ​​or updated values: trigger time value, incremental value, or threshold for handover of user equipment.

[0060] about Figure 3 The method is that, compared with the non-relaxed handover requirements, the relaxed handover requirements for LTM handover configuration of user equipment are easier to meet, so as to more easily trigger LTM handover to the second target cell based on L1 measurement reports, or compared with the non-relaxed handover requirements, the relaxed handover requirements for LTM handover configuration trigger LTM handover of user equipment to the second target cell based on a wider range of L1 measurements.

[0061] about Figure 3 The method, LTM switching configuration, is user-specific to the device.

[0062] about Figure 3The method may include: the source centralization unit detecting, based on the reception of an L3 measurement report, that the user equipment is under radio conditions below a predetermined threshold relative to the serving cell; and the source centralization unit transmitting, based on the detection, an LTM handover configuration for a second target cell to the source distribution unit.

[0063] about Figure 3 The method may include: the source centralization unit detecting, based on the reception of an L3 measurement report, that the user equipment is in a radio condition below a predetermined threshold relative to the serving cell; the source centralization unit confirming, based on the reception of an L3 measurement report, that the source centralization unit has not yet received an indication for LTM handover of the user equipment from the serving cell to a second target cell; and the source centralization unit sending an LTM handover configuration for the second target cell to the source distribution unit based on the detection and confirmation.

[0064] about Figure 3 The method for LTM switching configuration also includes timer values ​​to be used for the validity timer.

[0065] about Figure 3 The method for LTM handover configuration for LTM handover from user equipment to a second target cell is an intermediate step handover or a transitional step handover, in order to reduce the likelihood of radio link failure of user equipment before user equipment performs handover to the first target cell based on the handover configuration for the first target cell.

[0066] Figure 4 This is a flowchart illustrating the operation of a source distribution unit according to an example embodiment. Operation 410 includes: the source distribution unit associated with the serving cell receiving a Layer 1 / Layer 2 triggered Mobility (LTM) LTM handover configuration and a timer value from a source central unit. This LTM handover configuration has lenient handover requirements for LTM handover from the user equipment to the target cell. The timer value is used for an effectiveness timer of the LTM handover configuration, where the target cell is associated with both the source central unit and a different distribution unit. Operation 420 includes: the source central unit starting an effectiveness timer for the LTM handover configuration, the effectiveness timer indicating the validity period of the LTM handover configuration. Operation 430 includes: the source distribution unit receiving a Layer 1 measurement report from the user equipment before the effectiveness timer of the LTM handover configuration expires. Operation 440 includes: the source distribution unit determining, based on the Layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met. And, operation 450 includes: the source distribution unit sending a Media Access Control (MAC) control element to the user equipment to trigger the user equipment to perform an LTM handover to the target cell.

[0067] Figure 5A To Figure 5D ( Figure 5A , Figure 5B , Figure 5CFigure 5D is a diagram illustrating network operation according to an example embodiment. Figure 5A As shown in Figure 5D, before the UE performs an L3 HO or CHO to the cell associated with the target CU 220, an intermediate LTM handover is performed from the UE to the second target cell associated with the source CU 210.

[0068] refer to Figure 5A As shown in Figure 5D, UE 510 can initially be served by a source distribution unit (source DU 512), which is associated with or controlled by source CU 210. Target DU 514 is also associated with or controlled by source CU 210. Target DU 516 is associated with or controlled by target CU 220. In steps 1 and 2, an L3 measurement report is sent from UE 510 to source DU 512 and forwarded to source CU 210. In step 3, source CU 210 performs LTM candidate preparation, including sending a UE context establishment request to target DU 514 and receiving a UE context establishment response. In steps 6 and 7, source CU 210 sends a UE context modification request to source DU 512 and receives a UE context modification response. In step 8, source CU 210 generates an RRC reconfiguration message, including: 1) a measurement configuration for L1 cell handover, which provides the UE with a measurement configuration for performing L1 measurements, and 2) the configuration of prepared candidate LTM cells (e.g., each configuration may include the candidate / target cell's beam, the candidate cell's bandwidth, the candidate cell's access information (such as a random access preamble), and / or other information or parameters that the UE may need to communicate with the cell and / or perform a handover to the cell). In steps 9 and 10, source CU 210 sends the generated RRC reconfiguration message to UE 510 via source DU 512. In steps 11 and 12, source CU 210 receives an RRC reconfiguration completion message from UE 510. In step 13, the UE sends an L1 measurement report to source DU 512. In steps 14 and 15, the UE performs downlink (DL) synchronization with the candidate cell based on the LTM candidate configuration and performs timing advance (TA) acquisition with the candidate cell. Therefore, at this point, an LTM HO configuration has been prepared for UE510 for a group (e.g., a group of 8) of LTM HO candidate / target cells, which are associated with the source CU 210.

[0069] about Figure 5A Referring to Figure 5D, in steps 16 and 17, the source CU receives an L3 measurement report from UE 510. For example, the L3 measurement report may include signal measurements, wherein the first target cell (e.g., cell 4) is associated with the target DU 516 of the target CU 220. Figure 2The L3 measurement report provided by the UE can indicate the strongest or best signal measurement. Therefore, in this example, the first target cell (cell 4) is not associated with the source CU 210, but with the target CU 220. Thus, the L3 measurement report provided by the UE can provide L3 cell measurements, which indicate (or the source CU 210 can determine based on the L3 measurements) the preferred HO (House of Interest) for the UE to the first target cell (e.g., the signal measurement of cell 4 meets the HO event criteria, and / or provides the best cell for the UE). The first target cell is associated with (e.g., controlled by) the target CU 220, which is different from the UE's current source CU 210 (therefore, an LTM HO to the first target cell or cell 4 is not possible, and the HO to the first target cell or cell 4 should be performed via an L3 HO or a CHO). However, in this example, the source CU 210 can also confirm that an LTM HO for the UE to the cell associated with the source CU 210 has not yet been triggered for the UE. Therefore, according to the example embodiment, the source CU 210 can: a) receive an L3 measurement report from the UE, and based on this L3 measurement report, the source CU 210 determines that an HO / CHO should be performed for the UE to the first target cell (because cell 4 meets the HO event criteria, for example, the RSRP of cell 4 is better than the RSRP of the current serving cell 3 by more than a threshold, and the source CU 210 also knows that cell 4 is not associated with the source CU 210, but with the target CU 220, therefore, an LTM HO to cell 4 is impossible); and b) the source CU 210 determines, based on the L3 measurement report, that the UE is associated with the current serving cell 3 (cell 3, Figure 2 If the current radio conditions (e.g., RSRP or RSRQ) of the radio link between the UE and the source CU 210 are less than a threshold (e.g., indicating a significant or enhanced risk of RLF for the UE), the source CU 210 should perform or configure an emergency (or intermediate) LTM HO using a lenient LTM HO requirement. A lenient LTM HO requirement encourages or makes it more likely that the UE will perform a handover to a second target cell (e.g., cell 2, or other cells that meet such a lenient HO requirement) associated with the source CU 210 (to a cell associated with the same CU (source CU 210) as the serving cell), or to a cell where the UE already has an LTM HO configuration.

[0070] Therefore, in Figure 5A In step 18 of Figure 5D, source CU 210 determines to modify (or provide) the LTM HO configuration at source DU 512 (e.g., to change the behavior of DU 512), with relaxed HO requirements, for use with the target cell (e.g., cell 2) associated with source CU 210. Figure 2The source CU210 performs an emergency (or intermediate) LTM HO, for example, to make it more likely that the UE will perform an intermediate or emergency LTM HO to the cell associated with the source CU210 (for which the UE 510 has prepared an LTM HO configuration). Simultaneously, the source CU210 determines candidate cells to prepare for L3 HO or CHO, for example, including for the first target cell (cell 4) (see steps 21 to 25 to prepare the HO / CHO configuration for L3 HO or CHO to the first target cell (e.g., cell 4)). Furthermore, at this time, the source CU210 starts a validity timer CU-X, which indicates the validity period of an LTM HO configuration with relaxed HO requirements (e.g., an updated one).

[0071] In step 19, source CU 210 may send an updated LTM HO configuration for the UE to source DU 512 associated with the serving cell, including a relaxed HO requirement for the UE to make an LTM HO to the cell associated with source CU 210. The relaxed HO requirement makes source DU 512 (the serving UE) more likely to trigger an LTM HO based on an L1 measurement report to one of the cells already configured with an LTM HO (e.g., cell 1 or cell 2, associated with source CU 210) and / or otherwise to the cell associated with source CU 210.

[0072] In step 20, source DU 512 receives an LTM HO configuration with a relaxed HO requirement and starts validity timer DU-X (which is synchronized with validity timer CU-X used by source CU 210) to indicate the validity period of the received LTM HO configuration that includes the relaxed LTM HO requirement.

[0073] Preparation of the L3 HO or CHO configuration for the first target cell (e.g., cell 4) is performed via messages 21 to 25, wherein the source CU 210 sends a handover request (for HO or CHO) to the target CU 220. In step 26, based on the preparation of at least the HO command or CHO configuration for the target cell (e.g., cell 4), the source CU 210 now prepares an RRC reconfiguration message for the L3 HO or CHO to the first target cell (e.g., cell 4) associated with the target CU 220. In a first example embodiment, CU 210 may immediately send or forward the RRC reconfiguration message (including the HO command or CHO configuration) to the source DU 512 and / or the target DU 514. However, in a second example embodiment, the source CU 210 does not yet forward (but waits to forward) the RRC reconfiguration message (including the HO command or CHO configuration) to the source DU 512 (associated with the UE's serving cell) or the target DU 514 (associated with the second target cell, e.g., cell 4). Figure 2Cell 2 in the example). Conversely, in this second example embodiment, source CU210 may wait for either of the following conditions to occur before forwarding the RRC reconfiguration message: 1) The validity timer expires (before receiving the LTM HO indication) (in this case, the RRC reconfiguration message, including the L3 HO command or CHO configuration, will be sent to source DU 512 associated with source CU 210 because the LTM HO to the second target cell, for example to cell 2, was not executed based on the lenient HO requirement, as shown in the example). Figures 6A to 6C ); or 2) Source CU 210 receives an LTM HO (or LTM cell handover) indication from source DU 512, instructing the UE to move to the second target cell (e.g., cell 2, Figure 2 The LTM HO has been triggered, and the second target cell is associated with the source CU 210. (In this case, the RRC reconfiguration message, including the L3 HO command or CHO configuration, will be sent to the target DU 514 (the DU associated with the cell to which the UE performed the LTM HO). The target DU 514 is associated with the source CU 210 because the LTM HO to the second target cell or cell 2 has been performed. This situation is shown in...) Figure 5A (See Figure 5D). Therefore, according to the example embodiment, the source CU 210 may wait to forward an RRC reconfiguration message with HO command / CHO configuration for L3 HO or CHO until the source CU 210 knows where to forward the HO command / CHO configuration for L3 HO or CHO (until the source CU 210 knows whether LTM HO has been executed).

[0074] In step 27, source DU512 may receive and evaluate any L1 measurement reports received from UE510 to determine whether the relaxed HO requirement is met for any cell associated with source CU210. In step 28, source DU512 determines that the relaxed HO requirement is met for a certain cell (e.g., cell 2 associated with source CU210), and then triggers UE LTM HO for that cell (e.g., cell 2) (because the relaxed HO requirement is met for this cell). Validity timer DU-X is stopped.

[0075] In step 29, source DU 512 sends an LTM HO indication to source CU 210, indicating that the UE's LTM HO (e.g., to a second target cell or cell 2) has been triggered (the target cell to which the LTM HO is performed and / or DU (DU 514) can be provided or indicated to source CU 210), and in step 30, source CU 210 stops its validity timer CU-X. In step 31, source DU 512 sends a MAC control element (MAC CE) to trigger UE 510 to perform an LTM HO to the indicated second target cell (e.g., to cell 2), the second target cell being associated with source CU 210 and target DU 514. In step 32, UE 510 performs random access to the second target cell (e.g., cell 2) associated with source CU 210. In steps 33 and 34, the UE notifies source CU 210 via target DU 514 that the RRC reconfiguration is complete (the UE's LTM HO to the second target cell is complete).

[0076] In steps 33 and 34, UE 510 provides an RRC reconfiguration completion message to source CU 210. In steps 35 and 36, after source CU 210 receives (in step 29) an LTM HO indication indicating that the UE's LTM HO (e.g., to the second target cell or cell 2) has been triggered, source CU 210 sends an RRC reconfiguration message, including an L3 HO command or CHO configuration, to target DU 514 associated with source CU 210, because the LTM HO to the second target cell or cell 2 (associated with target DU 514 and source CU 210) has been executed. UE 510 acknowledges receipt of the RRC reconfiguration message in steps 37 and 38, and UE 510 releases the context with source CU 210 in steps 39 and 40 for the previous connection to the cell of source DU 512. After completing an intermediate or emergency HO to the second target cell (e.g., a HO to cell 2), an RRC reconfiguration message including an HO command or CHO configuration is used for the L3 HO or CHO to cause UE510 to execute an L3 HO or CHO to the first target cell (e.g., cell 4, as shown in the diagram). Figure 2 (This is shown as step 41 via target CU 220).

[0077] Figure 5A The steps leading to Figure 5D can be summarized as follows: Steps 1 through 15: Perform LTM preparation and early synchronization / The UE also provides L1 measurements.

[0078] Steps 16 to 17: The UE sends an L3 measurement report for the new cell (which may belong to another CU) because the radio conditions have deteriorated and the LTM conditions are not met.

[0079] Step 18: The source CU decides to modify the LTM configuration for emergency LTM at the source DU, while preparing candidate cells for handover (e.g., CHO). At the same time, it starts timer CU-X.

[0080] Step 19: The CU indicates to the S-DU the new threshold for LTM and the timer value X (DU-X). The new LTM threshold is valid until the timer expires.

[0081] Step 20: Start timer DU-X with S-DU. Note that timers CU-X and DU-X can have the same value; they are designed to enable coordinated operation between CU and DU.

[0082] Steps 21 to 26: Initiate handover preparations to all selected new CU candidate cells in parallel (started in step 18).

[0083] Step 27: The UE sends an L1 measurement report to the S-DU (this may occur in parallel with steps 21 to 26).

[0084] Step 28: The S-DU considers the new LTM threshold of the candidate cell and makes an (emergency) serving cell handover decision. Stop timer DU-X.

[0085] Step 29: Notify the source CU that the cell handover command has been triggered.

[0086] Step 30: Stop timer CU-X after receiving the cell handover trigger indication.

[0087] Steps 31 to 34: LTM switch execution.

[0088] Steps 35 to 38: Reconfiguration process for CHO or BSO.

[0089] Steps 39 to 40: Release the UE context at the S-DU.

[0090] Step 41: The UE and the target CU execute a CHO.

[0091] Figures 6A to 6C ( Figure 6A , Figure 6B and Figure 6C ( ) is a diagram illustrating network operation according to another example embodiment. Figures 6A to 6C In the previous scenario, an intermediate or emergency LTM handover was configured for the UE to the second target cell associated with source CU 210 but was not executed. Then, after the validity timer for the relaxed LTM HO requirement expired, the UE executed an L3 HO or CHO to the cell associated with target CU 220. A brief description will follow. Figures 6A to 6C Zhongyu Figure 5AThe steps are different from those in Figure 5D. Figures 6A to 6C Steps 1 to 26 and Figure 5A Steps 1 through 26 of Figure 5D are largely the same. In step 27, the validity timer DU-X at source DU 512 expires and the LTM HO to the second target cell is not executed, and source DU 512 is restored to the LTM HO configuration using non-relaxed HO requirements (e.g., the previous or default configuration). Similarly, in step 28, the validity timer CU-X at source CU 210 expires (source CU 210 does not receive an LTM HO indication for UE 510 (therefore, the LTM HO for UE to the second target cell is not executed). In steps 29 and 30, after the validity timer CU-X expires, source CU 210 sends an RRC reconfiguration message including an L3 HO command or CHO configuration to source DU 512 associated with source CU 210. Because the LTM HO for the second target cell or cell 2 (associated with DU 514 and source CU 210) was not executed, UE 510 is still served by the serving cell associated with source DU 512. The message is sent from source CU 210 to source DU 512. The RRC message of 512, which includes an HO command or CHO configuration, may include a complete configuration, such as values ​​for all configured parameters. And / or, the RRC message may include an incremental configuration, which includes one or more updated parameters (e.g., only configuration parameters that have changed or are different relative to a reference configuration) for the UE to the first target cell's HO, wherein one or more updated parameters reference a complete configuration known to the UE, where the complete configuration corresponds to the configuration of the serving cell associated with the source DU 512 (current serving UE 510).

[0092] Figures 6A to 6C The operation can be summarized as follows: Steps 1 through 15: Perform LTM preparation and early synchronization / The UE also provides L1 measurements.

[0093] Steps 16 to 17: Due to deteriorating radio conditions and failure to meet the LTM conditions, the UE sends an L3 measurement report for the new cell (which may belong to another CU).

[0094] Step 18: The source CU decides to modify the LTM configuration at the source DU for emergency LTM, while preparing candidate cells for handover (e.g., CHOs with incremental / full configurations), optionally considering the serving cell as a reference for CHOs / other basic handovers (BHOs). Timer CU-X is started simultaneously.

[0095] Step 19: The CU indicates to the S-DU the new threshold for LTM and the timer value X (DU-X). The new LTM threshold is valid until the timer expires.

[0096] Step 20: S-DU starts timer DU-X. Note that timers CU-X and DU-X have the same value, which enables CU and DU to operate in a coordinated manner.

[0097] Steps 21 to 26: Initiate handover preparation with full / incremental configurations in parallel to all selected new inter-CU candidate cells (started in step 18).

[0098] Step 27: Timer DU-X expires. S-DU discards the emergency LTM threshold and considers the previously sent LTM threshold.

[0099] Step 28: Timer CU-X expires at S-CU. The RRC configuration for CHO / BHO (incremental if available, full configuration otherwise) is sent to the UE via S-DU.

[0100] Steps 29 to 32: RRC reconfiguration process for CHO / other BHO via source DU.

[0101] Step 33: Perform CHO with the target CU. In the case of BHO, the RRC reconfiguration in step 30 should be sent to the target CU via the target DU under the target CU.

[0102] Figures 7A to 7C ( Figure 7A , Figure 7B and Figure 7C ( ) is a diagram illustrating network operation according to another example embodiment. Figures 7A to 7C The steps can be summarized as follows: Steps 1 through 15: Perform LTM preparation and early synchronization / The UE also provides L1 measurements.

[0103] Steps 16 to 17: Due to deteriorating radio conditions and failure to meet the LTM conditions, the UE sends an L3 measurement report for the new cell (which may belong to another CU).

[0104] Step 18: The source CU decides to modify the LTM configuration at the source DU for emergency LTM, and prepares candidate cells (e.g., CHO) for handover. At the same time, timer CU-X is started.

[0105] Step 19: The CU indicates to the S-DU the new threshold for LTM and the timer value X. The new LTM threshold is valid until the timer expires.

[0106] Step 20: S-DU starts timer DU-X. Note that timers CU-X and DU-X have the same value, which enables CU and DU to operate in a coordinated manner.

[0107] Steps 21 to 26: Initiate handover preparation in parallel to all selected new inter-CU candidate cells (started in step 18).

[0108] Step 27: The UE sends an L1 measurement report to the S-DU (source DU) (which can occur in parallel with steps 21 to 26).

[0109] Step 28: S-DU considers the new LTM threshold of the candidate cell, makes an (urgent) serving cell change decision, and stops timer DU-X.

[0110] Step 29: Notify the source CU that the cell handover command has been triggered.

[0111] Step 30: Stop timer CU-X after receiving the cell change trigger indication.

[0112] Step 31: Send RRC reconfiguration to the target DU in the UE context modification request to be sent to the UE after LTM execution is completed (after receiving the first UL SRB data).

[0113] Steps 32 to 34: LTM switch execution.

[0114] Steps 35 to 38: RRC reconfiguration process for CHO / basic HO commands.

[0115] Steps 39 to 40: Release the UE context at the S-DU.

[0116] Step 41: The UE and the target CU execute a CHO.

[0117] Figures 8A to 8D This illustrates network operation according to yet another example embodiment. The following is a summary. Figures 8A to 8C The operation.

[0118] Steps 1 through 15: Perform LTM preparation and early synchronization / The UE also provides L1 measurements.

[0119] Steps 16 to 17: Due to deteriorating radio conditions and failure to meet the LTM conditions, the UE sends an L3 measurement report for the new cell (which may belong to another CU).

[0120] Step 18: The source CU decides to modify the LTM configuration for emergency LTM at the source DU, and prepares candidate cells for handover (e.g., CHO). At the same time, timer CU-X is started.

[0121] Step 19: The CU indicates to the S-DU the new threshold for LTM and the timer value X. The new LTM threshold is valid until the timer expires.

[0122] Step 20: S-DU starts timer DU-X. Note that timers CU-X and DU-X have the same value, which enables CU and DU to operate in a coordinated manner.

[0123] Step 21: The source CU predicts possible LTM target candidates and uses them as a reference for the CHO / other baseline HOs. Alternatively, it can prepare a reference template configuration for incremental configuration preparation.

[0124] Steps 22 to 27: Initiate handover preparation in parallel for all selected new inter-CU candidate cells, with the target CU being a CHO or other baseline HO, and prepare incremental and full configurations.

[0125] Step 28: The UE sends an L1 measurement report to the S-DU (this may occur in parallel with steps 21 to 26).

[0126] Step 29: S-DU considers the new LTM threshold of the candidate cell, makes an (urgent) serving cell change decision, and stops timer DU-X.

[0127] Step 30: Notify the source CU that the cell handover command has been triggered.

[0128] Step 31: Timer CU-X stops. RRC reconfiguration should be sent along with incremental configuration (if the predicted LTM candidate is successful) or full configuration (if the prediction of the LTM target candidate is incorrect).

[0129] Step 32: Send RRC reconfiguration to the target DU in the UE context modification request to be sent to the UE after LTM execution is completed (after receiving the first UL SRB data).

[0130] Steps 33 to 35: LTM switch execution.

[0131] Steps 36 to 39: RRC reconfiguration process for CHO / basic HO commands.

[0132] Steps 40 to 41: Release the UE context at the S-DU.

[0133] Step 42: The UE and the target CU execute a CHO.

[0134] exist Figures 8A to 8DIn the steps, in step 21, source CU 210 predicts possible target LTM candidates for an emergency or intermediate HO for the UE (e.g., predicting an LTM HO to a second target cell associated with source CU 210, such as cell 2). In step 23, target CU 220 prepares incremental and full configurations considering the serving cell and the predicted LTM HO candidate cells. In step 30, source CU receives a cell change / LTM HO indication. Source CU 210 sends an HO command or CHO configuration via an RRC reconfiguration message, which includes the full configuration (if the predicted LTM HO cell is incorrect) or an incremental configuration relative to the full configuration the UE has for the predicted LTM HO cell (if the predicted cell for the LTM HO (e.g., cell 2)) Therefore, the RRC message sent by the source CU, which includes the HO command or CHO configuration, may include an incremental configuration that includes one or more updated parameters for the HO of the UE to the first target cell, wherein the one or more updated parameters refer to the complete configuration known to the UE, wherein the complete configuration corresponds to the configuration of the serving cell associated with the target DU 514 (i.e. the serving cell now serving UE 510 after the LTM HO is performed).

[0135] For example, if source CU 210 has predicted UE movement (e.g., performing an LTM HO) to cell 2, source CU 210 can prepare an incremental configuration for target cell 4 relative to the configuration of cell 2. However, if the UE does not perform an LTM HO at all or has performed an LTM HO to another cell other than cell 2, the prepared incremental configuration for target cell 4 may not be used (because the UE may have released the configuration of cell 2 when moving out of cell 2). In this case, source CU 210 sends the complete configuration of cell 4 to the UE, which consumes more resources than sending only the incremental configuration. Therefore, there can be benefits to having an incremental configuration prepared when the prediction of UE movement is correct. Note that source CU 210 can prepare multiple incremental configurations for cell 4, each relative to a different cell. For example, source CU 210 can prepare a first incremental configuration for cell 4 indicating a parameter offset relative to cell 2, and a second incremental configuration for cell 4 indicating a parameter offset relative to cell 3. Then, if the UE does not perform an LTM HO to leave cell 3 or to enter cell 2, the corresponding incremental configuration can be included in the RRC reconfiguration message that configures the UE to have a cell 4 configuration.

[0136] Some examples will now be described based on the descriptions and figures provided in this article.

[0137] Example 1. 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 a Layer 3 measurement report from a user equipment via a source centralization unit, the Layer 3 measurement report providing results of radio signal measurements of at least one cell; determine, based on the Layer 3 measurement report, that a handover should be performed for the user equipment from a serving cell associated with the source centralization unit to a first target cell associated with a target centralization unit, wherein a handover configuration for the handover from the user equipment to the first target cell has not yet been prepared, wherein the target centralization unit is different from the source centralization unit; determine, based on the received Layer 3 measurement report, that a Layer 1 / Layer 2 triggered mobility (LTM) LTM handover configuration with relaxed handover requirements for an LTM handover from the user equipment to a second target cell is provided to the source centralization unit associated with the serving cell, wherein the second target cell is also associated with the source centralization unit; transmit the LTM handover configuration for the second target cell to the source centralization unit; and transmit a handover request to the target centralization unit associated with the first target cell to prepare a handover configuration for the user equipment to perform a handover to the first target cell.

[0138] Example 2. The apparatus according to Example 1, wherein the apparatus is further configured to: initiate a validity timer for the LTM handover configuration by the source centralization unit, indicating the validity period of the LTM handover configuration.

[0139] Example 3. The apparatus according to Example 2, wherein the apparatus is further configured such that: when a determination is made to provide an LTM handover configuration to the source distribution unit, an validity timer for the LTM handover configuration is started by the source centralization unit.

[0140] Example 4. The apparatus according to any one of Examples 2 to 3, wherein the apparatus is further configured such that: the handover of the user equipment to the first target cell is performed after either: 1) the validity timer expires, or 2) the user equipment performs an LTM handover to the second target cell based on the LTM handover configuration for the second target cell.

[0141] Example 5. An apparatus according to any one of Examples 2 to 4, wherein the apparatus is configured to: receive an LTM handover indication from a source centralization unit, the LTM handover indication indicating that an LTM handover from a user equipment to a second target cell has been triggered; and send a radio resource control (RRC) message including a handover command or conditional handover configuration from the source centralization unit to a source distribution unit associated with the second target cell, to instruct the user equipment to perform a handover or conditional handover to a first target cell associated with the target centralization unit.

[0142] Example 6. The apparatus according to Example 5, wherein the apparatus is configured to: stop the validity timer for LTM handover configuration received based on the LTM handover indication.

[0143] Example 7. An apparatus according to any one of Examples 2 to 4, wherein the apparatus is configured to: detect the expiration of a validity timer for an LTM handover configuration before an LTM handover indication indicating that an LTM handover to a second target cell has been triggered; and send a radio resource control (RRC) message, including a handover command or conditional handover configuration, from the source centralization unit to the source distribution unit associated with the second target cell, to instruct the user equipment to perform a handover or conditional handover to a first target cell associated with the target centralization unit.

[0144] Example 8. The apparatus according to Example 7, wherein the RRC message includes an incremental configuration, the incremental configuration including one or more updated parameters for handover of the user equipment to a first target cell, the one or more updated parameters referencing a complete configuration known to the user equipment, wherein the complete configuration corresponds to the configuration of the serving cell.

[0145] Example 9. The apparatus according to Example 7, wherein the RRC message includes an incremental configuration, the incremental configuration including one or more updated parameters for handover of the user equipment to a first target cell, the one or more updated parameters referencing a complete configuration known to the user equipment, wherein the complete configuration corresponds to the configuration of the second target cell.

[0146] Example 10. The apparatus according to Example 9, wherein after the user equipment performs a handover from the serving cell to the second target cell, the user equipment uses incremental configuration for the handover to the first target cell.

[0147] Example 11. An apparatus according to any one of Examples 1 to 10, wherein the LTM handover configuration includes one or more of the following values ​​or updated values: a trigger time value, an incremental value, or a threshold value for handover of the user equipment.

[0148] Example 12. The apparatus according to any one of Examples 1 to 11, wherein the relaxed handover requirements for the LTM handover configuration of the user equipment are easier to meet than the non-relaxed handover requirements, so that the LTM handover to the second target cell is more easily triggered based on the L1 measurement report, or the relaxed handover requirements for the LTM handover configuration trigger the LTM handover of the user equipment to the second target cell based on a wider range of L1 measurements compared to the non-relaxed handover requirements.

[0149] Example 13. An apparatus according to any one of Examples 1 to 12, wherein the LTM switching configuration is user-specific to the device.

[0150] Example 14. An apparatus according to any one of Examples 1 to 13, wherein the apparatus is configured to: detect, by the source centralization unit, that the user equipment is in a radio condition below a predetermined threshold relative to the serving cell based on the reception of an L3 measurement report; and transmit, by the source centralization unit, an LTM handover configuration for a second target cell to the source distribution unit based on the detection.

[0151] Example 15. An apparatus according to any one of Examples 1 to 14, wherein the apparatus is configured such that: the source centralization unit detects, based on the reception of an L3 measurement report, that the user equipment is in a radio condition below a predetermined threshold relative to the serving cell; the source centralization unit confirms, based on the reception of an L3 measurement report, that the source centralization unit has not yet received an indication for LTM handover of the user equipment from the serving cell to a second target cell; and the source centralization unit transmits an LTM handover configuration for the second target cell to the source distribution unit based on the detection and confirmation.

[0152] Example 16. An apparatus according to any one of Examples 1 to 15, wherein the LTM handover configuration for LTM handover from the user equipment to the second target cell is an intermediate step handover or a transitional step handover, in order to reduce the likelihood of radio link failure of the user equipment before the user equipment performs a handover to the first target cell based on the handover configuration for the first target cell.

[0153] Example 17. A method comprising: receiving a Layer 3 measurement report from a user equipment via a source centralization unit via a source distribution unit, the Layer 3 measurement report providing results of radio signal measurements of at least one cell; determining, based on the Layer 3 measurement report, that a handover should be performed for the user equipment from a serving cell associated with the source centralization unit to a first target cell associated with a target centralization unit, wherein a handover configuration for the handover to the first target cell is not yet ready, wherein the target centralization unit is different from the source centralization unit; determining, based on the received Layer 3 measurement report, to provide a Layer 1 / Layer 2 Triggered Mobility (LTM) LTM handover configuration to the source distribution unit associated with the serving cell, the configuration having relaxed handover requirements for the user equipment to perform an LTM handover to a second target cell, wherein the second target cell is also associated with the source centralization unit; transmitting the LTM handover configuration for the second target cell to the source distribution unit; and transmitting a handover request to the target centralization unit associated with the first target cell to prepare a handover configuration for the user equipment to perform a handover to the first target cell.

[0154] Example 18. The method according to Example 17 further includes: starting a validity timer for the LTM handover configuration by a source central unit, the validity timer indicating a validity period of the LTM handover configuration.

[0155] Example 19. The method according to any one of Examples 17 to 18 further includes: when a determination is made to provide an LTM handover configuration to the source distribution unit, the source central unit starts an validity timer for the LTM handover configuration.

[0156] Example 20. The method according to any one of Examples 18 to 19 further includes: wherein the handover of the user equipment to the first target cell is performed after either: 1) the validity timer expires, or 2) the user equipment performs an LTM handover to the second target cell based on the LTM handover configuration for the second target cell.

[0157] Example 21. The method according to any one of Examples 18 to 20 further includes: receiving an LTM handover indication from a source centralization unit, the LTM handover indication indicating that an LTM handover from a user equipment to a second target cell has been triggered; and sending a radio resource control (RRC) message from the source centralization unit to a source distribution unit associated with the second target cell, the RRC message including a handover command or conditional handover configuration to instruct the user equipment to perform a handover or conditional handover to a first target cell associated with the target centralization unit.

[0158] Example 22. The method according to Example 21 further includes: stopping the validity timer for LTM handover configuration based on the receipt of the LTM handover indication.

[0159] Example 23. A method according to any one of Examples 18 to 22, comprising: detecting that a validity timer for LTM handover configuration has expired prior to an LTM handover indication indicating that an LTM handover to a second target cell has been triggered; and sending a Radio Resource Control (RRC) message from a source centralization unit to a source distribution unit associated with the second target cell, the RRC message including a handover command or conditional handover configuration to instruct the user equipment to perform a handover or conditional handover to a first target cell associated with the target centralization unit.

[0160] Example 24. The method according to Example 23, wherein the RRC message includes an incremental configuration that includes one or more updated parameters for handover of the user equipment to a first target cell, the one or more updated parameters referencing a complete configuration known to the user equipment, wherein the complete configuration corresponds to the configuration of the serving cell.

[0161] Example 25. The method according to Example 23, wherein the RRC message includes an incremental configuration that includes one or more updated parameters for handover of the user equipment to a first target cell, the one or more updated parameters referencing a complete configuration known to the user equipment, wherein the complete configuration corresponds to the configuration of the second target cell.

[0162] Example 26. The method according to Example 25, wherein after the user equipment performs a handover from the serving cell to the second target cell, it uses an incremental configuration for the handover to the first target cell.

[0163] Example 27. The method according to any one of Examples 17 to 26, wherein the LTM handover configuration includes one or more of the following values ​​or updated values: a trigger time value, an incremental value, or a threshold value for handover of the user equipment.

[0164] Example 28. The method according to any one of Examples 17 to 27, wherein the relaxed handover requirements for the LTM handover configuration of the user equipment are easier to meet than the non-relaxed handover requirements, so as to more easily trigger the LTM handover to the second target cell based on the L1 measurement report, or the relaxed handover requirements for the LTM handover configuration trigger the LTM handover to the second target cell based on a wider range of L1 measurements compared to the non-relaxed handover requirements.

[0165] Example 29. The method according to any one of Examples 17 to 28, wherein the LTM switching configuration is user-specific to the device.

[0166] Example 30. The method according to any one of Examples 17 to 29, comprising: detecting, by the source centralization unit, based on the reception of an L3 measurement report, that the user equipment is under radio conditions below a predetermined threshold relative to the serving cell; and transmitting, by the source centralization unit, an LTM handover configuration for a second target cell to the source distribution unit based on the detection.

[0167] Example 31. The method according to any one of Examples 17 to 30, comprising: the source centralization unit detecting, based on the reception of an L3 measurement report, that the user equipment is under radio conditions below a predetermined threshold relative to the serving cell; the source centralization unit confirming, based on the source centralization unit not having received an indication for LTM handover of the user equipment from the serving cell to a second target cell; and the source centralization unit sending an LTM handover configuration for the second target cell to the source distribution unit based on the detection and confirmation.

[0168] Example 32. The method according to any one of Examples 17 to 31, wherein the LTM handover configuration for LTM handover from the user equipment to the second target cell is an intermediate step handover or a transitional step handover, in order to reduce the likelihood of radio link failure of the user equipment before the user equipment performs a handover to the first target cell based on the handover configuration for the first target cell.

[0169] Example 33. 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, from a source central unit a Layer 1 / Layer 2 triggered Mobility (LTM) LTM handover configuration and a timer value, by a source distribution unit associated with a serving cell, a Layer 1 / Layer 2 triggered LTM handover configuration having lenient handover requirements for an LTM handover from a user equipment to a target cell, and the timer value for the LTM handover configuration to be used for an effectiveness timer, wherein the target cell is associated with a source central unit and a different distribution unit; initiate an effectiveness timer for the LTM handover configuration by the source distribution unit, the effectiveness timer indicating a validity period of the LTM handover configuration; receive a Layer 1 measurement report from the user equipment by the source distribution unit before the effectiveness timer for the LTM handover configuration expires; determine, based on the Layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met by the source distribution unit; and send a Media Access Control (MAC) control element (MAC CE) to the user equipment by the source distribution unit to trigger the user equipment to perform an LTM handover to the target cell.

[0170] Example 34. The apparatus according to Example 33, wherein the target cell includes a second target cell, and wherein a handover configuration for handover to a first target cell associated with a target central cell has been prepared for the user equipment, wherein the LTM handover configuration for LTM handover from the user equipment to the second target cell is an intermediate step handover or a transitional step handover to reduce the likelihood of radio link failure of the user equipment before the user equipment performs a handover to the first target cell based on the handover configuration for the first target cell.

[0171] Example 35. A method includes: receiving, from a source central unit, a layer 1 / layer 2 triggered mobility (LTM) LTM handover configuration and a timer value, by a source distribution unit associated with a serving cell, a layer 1 / layer 2 triggered mobility (LTM) LTM handover configuration having lenient handover requirements for an LTM handover from a user equipment to a target cell, the timer value being used for an validity timer of the LTM handover configuration, wherein the target cell is associated with a source central unit and a different distribution unit; starting a validity timer for the LTM handover configuration by the source distribution unit, the validity timer indicating a validity period of the LTM handover configuration; receiving a layer 1 measurement report from the user equipment before the validity timer for the LTM handover configuration expires by the source distribution unit; determining, based on the layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met by the source distribution unit; and sending a media access control (MAC) control element to the user equipment to trigger the user equipment to perform an LTM handover to the target cell.

[0172] Example 36. The method according to Example 35, wherein the target cell includes a second target cell, and wherein a handover configuration for handover to a first target cell associated with a target central cell has been prepared for the user equipment, wherein the LTM handover configuration for LTM handover of the user equipment to the second target cell is an intermediate or transitional step handover to reduce the likelihood of radio link failure of the user equipment before the user equipment performs a handover to the first target cell based on the handover configuration for the first target cell.

[0173] Figure 9 This is a block diagram of a wireless station or node (e.g., UE, user equipment, AP, BS, eNB, gNB, RAN node, network node, TRP, or other node) 1300 according to an example embodiment. The wireless station 1300 may include, for example, one or more (e.g., such as...) Figure 9 The two RF (radio frequency) or wireless transceivers 1302A and 1302B shown are provided, each of which includes a transmitter for transmitting signals and a receiver for receiving signals. The wireless station also includes a processor or control unit / entity (controller) 1304 for executing instructions or software and controlling the transmission and reception of signals, and a memory 1306 for storing data and / or instructions.

[0174] Processor 1304 may also make decisions or determinations, generate frames, packets, or messages for transmission, decode received frames or messages for further processing, and perform other tasks or functions described herein. Processor 1304, for example, may be a baseband processor, and may generate messages, packets, frames, or other signals for transmission via wireless transceiver 1302 (1302A or 1302B). Processor 1304 may control the transmission of signals or messages through a wireless network and may control the reception of signals or messages, such as via a wireless network (e.g., after being down-converted by wireless transceiver 1302). Processor 1304 may be programmable and capable of executing software or other instructions stored in memory or other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 1304 may be (or may include) hardware, programmable logic, a programmable processor executing software or firmware, and / or any combination of these. Using other terminology, processor 1304 and transceiver 1302 together may be considered, for example, a wireless transmitter / receiver system.

[0175] In addition, refer to Figure 9 The controller (or processor) 1308 can execute software and instructions, and can provide overall control for station 1300, and can provide... Figure 9Other systems, not shown, provide control, such as controlling input / output devices (e.g., a display, a keyboard), and / or can execute software for one or more applications available on the wireless station 1300, such as, for example, an email program, an audio / video application, a word processor, a VoIP application, or other applications or software.

[0176] In addition, a storage medium may be provided, the storage medium including stored instructions, which, when executed by a controller or processor, may cause the processor 1304 or other controller or processor to perform one or more of the functions or tasks described above.

[0177] According to another example embodiment, the RF or wireless transceiver 1302A / 1302B can receive signals or data and / or send or transmit signals or data. The processor 1304 (and possibly the transceiver 1302A / 1302B) can control the RF or wireless transceiver 1302A or 1302B to receive, send, broadcast, or transmit signals or data.

[0178] Example embodiments are provided or described for each example method, including: apparatus (e.g., 1300, Figure 9 ), including components (e.g., processor 1304, RF transceiver 1302A and / or 1302B, and / or memory 1306, in Figure 9 (in the middle), used to execute any of the methods; a non-transient computer-readable storage medium (e.g., memory 1306, Figure 9 ), including instructions stored thereon, which, when processed by at least one processor (processor 1304, Figure 9 When executed, it is configured to cause the computing system or device (e.g., 1300, Figure 9 ) execute any example method; and the device (e.g., 1300, Figure 9 ), including at least one processor (e.g., processor 1304, Figure 9 ) and at least one memory (e.g., memory 1306, Figure 9 The at least one memory includes computer program code, and the at least one memory (1306) and the computer program code are configured together with at least one processor (1304) to cause the device (e.g., 1300) to perform at least any of the example methods.

[0179] Embodiments of the various technologies described herein can be implemented in digital electronic circuits, or in computer hardware, firmware, software, or a combination thereof. Embodiments can be implemented as computer program products, i.e., computer programs tangibly embodied in an information carrier, such as in a machine-readable storage device or in a transmitted signal, for execution by or control of the operation of a data processing device, such as a programmable processor, computer, or a plurality of computers. Embodiments can also be provided on a computer-readable medium or a computer-readable storage medium, which may be a non-transient medium. Embodiments of the various technologies may also include embodiments provided via transient signals or media, and / or program and / or software embodiments downloadable via the Internet or other networks, whether wired or wireless. Furthermore, embodiments can be provided via machine-type communication (MTC) or via the Internet of Things (IoT).

[0180] As used herein, the term "circuit system" or "circuit" means all of the following: (a) hardware circuit implementations only, such as implementations only in analog and / or digital circuits; and (b) combinations of circuits and software (and / or firmware), such as (if applicable): (i) combinations of processors or (ii) portions of processor / software, including digital signal processors, software, and memory, which work together to enable a device to perform various functions; and (c) circuits, such as microprocessors or portions of microprocessors, which require software or firmware to operate, even if the software or firmware is not physically present. This definition of "circuit system" applies to all uses of the term in this application. As a further example, as used herein, the term "circuit system" will also cover implementations only of processors (or processors) or portions of processors and their accompanying software and / or firmware. For example, if applicable to a particular element, the term "circuit system" will also cover baseband integrated circuits or application processor integrated circuits for mobile phones, or similar integrated circuits in servers, cellular network devices, or other network devices.

[0181] Computer programs can be in the form of source code, object code, or some intermediate form, and they can be stored on some carrier, distribution medium, or computer-readable medium, which can be any entity or device capable of carrying the program. Such carriers include, for example, recording media, computer memory, read-only memory, photoelectric and / or electrical carrier signals, telecommunication signals, and software distribution packages. Depending on the required processing power, a computer program can be executed in a single electronic digital computer, or it can be distributed among multiple computers.

[0182] Furthermore, embodiments of the various technologies described herein can utilize cyber-physical systems (CPS) (systems that control collaborative computing elements of physical entities). CPS enables the embodiment and utilization of a large number of interconnected ICT devices (sensors, actuators, processors, microcontrollers, etc.) embedded in physical objects in different locations. Mobile cyber-physical systems, where the physical systems under discussion possess inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robots and electronic devices transported by humans or animals. The proliferation of smartphones has increased interest in the field of mobile cyber-physical systems. Therefore, various embodiments of the technologies described herein can be provided via one or more of these technologies.

[0183] Computer programs, such as those described above, can be written in any programming language, including compiled or interpreted languages, and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units or parts thereof suitable for use in a computing environment. Computer programs can be deployed to execute on a single computer, or on multiple computers at a single site, or distributed across multiple sites interconnected by a communication network.

[0184] The method steps can be executed by one or more programmable processors that execute a computer program or a portion thereof by manipulating input data and generating output. The method steps can also be executed by special-purpose logic circuitry, and the apparatus can be implemented as special-purpose logic circuitry, such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit).

[0185] Processors suitable for executing computer programs include (by example) general-purpose and special-purpose microprocessors, as well as any type of digital computer, chip, or chipset and any one or more processors. Typically, a processor receives instructions and data from read-only memory or random access memory, or both. The components of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Typically, a computer may also include one or more mass storage devices for storing data, or be operatively coupled to one or more mass storage devices for storing data to receive data from or transfer data to, or both, such as magnetic disks, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including (by example) semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. Processors and memory may be supplemented by or incorporated into special-purpose logic circuitry.

[0186] To provide interaction with the user, embodiments can be implemented on a computer with a display device (such as a cathode ray tube (CRT) or liquid crystal display (LCD) monitor) for displaying information to the user, and a user interface (such as a keyboard and pointing device, such as a mouse or trackball), through which the user can provide input to the computer. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, voice, or tactile input.

[0187] The embodiments can be implemented in a computing system that includes backend components (e.g., as a data server), middleware components (e.g., an application server), or frontend components (e.g., a client computer with a graphical user interface or web browser through which a user can interact with the embodiments), or any combination of these backend, middleware, or frontend components. The components can be interconnected via digital data communication (e.g., a communication network) of any form or medium. Examples of communication networks include local area networks (LANs) and wide area networks (WANs), such as the Internet.

[0188] While certain features of the described embodiments have been illustrated herein, many modifications, substitutions, alterations, and equivalents will now occur to those skilled in the art. Therefore, it should be understood that the appended claims are intended to cover all such modifications and alterations falling within the true spirit of the various embodiments.

Claims

1. An apparatus comprising: At least one processor; as well as At least one memory stores instructions that, when executed by the at least one processor, cause the device to at least: The Layer 3 measurement report is received from the user equipment by the source centralization unit via the source distribution unit. The Layer 3 measurement report provides the results of radio signal measurements of at least one cell. The source centralization unit determines, based on the Layer 3 measurement report, that a handover should be performed for the user equipment from the serving cell associated with the source centralization unit to a first target cell associated with the target centralization unit, wherein the handover configuration for the handover from the user equipment to the first target cell has not yet been prepared, and wherein the target centralization unit is different from the source centralization unit; The source centralization unit determines, based on the received Layer 3 measurement report, a Layer 1 / Layer 2 triggered mobility LTM LTM handover configuration to the source distribution unit associated with the serving cell, the LTM handover configuration having lenient handover requirements for LTM handover from the user equipment to a second target cell, wherein the second target cell is also associated with the source centralization unit. The source centralization unit sends the LTM handover configuration for the second target cell to the source distribution unit; as well as The source centralization unit sends a handover request to the target centralization unit associated with the first target cell to prepare a handover configuration for the user equipment to perform a handover to the first target cell.

2. The apparatus of claim 1, wherein the apparatus is further configured to: The source central unit initiates a validity timer for the LTM handover configuration, the validity timer indicating a validity period for the LTM handover configuration.

3. The apparatus of claim 2, wherein the apparatus is further configured to: When a determination is made to provide the LTM handover configuration to the source distribution unit, the source centralization unit starts the validity timer for the LTM handover configuration.

4. The apparatus according to any one of claims 2 to 3, wherein the apparatus is further configured to: The handover from the user equipment to the first target cell is performed after either: 1) the expiration of the validity timer, or 2) the LTM handover from the user equipment to the second target cell based on the LTM handover configuration for the second target cell.

5. The apparatus according to any one of claims 2 to 4, wherein the apparatus is configured such that: The source centralization unit receives an LTM handover indication, which indicates that an LTM handover from the user equipment to the second target cell has been triggered; and The source centralization unit sends a Radio Resource Control (RRC) message to the source distribution unit associated with the second target cell. The RRC message includes a handover command or conditional handover configuration to instruct the user equipment to perform a handover or conditional handover to the first target cell associated with the target centralization unit.

6. The apparatus of claim 5, wherein the apparatus is configured to: The reception stops the validity timer used for the LTM handover configuration based on the LTM handover indication.

7. The apparatus according to any one of claims 2 to 4, wherein the apparatus is configured such that: Before the LTM handover indication is triggered to indicate that an LTM handover from the user equipment to the second target cell has been triggered, the expiration of the validity timer for the LTM handover configuration is detected; and The source centralization unit sends a Radio Resource Control (RRC) message to the source distribution unit associated with the second target cell. The RRC message includes a handover command or conditional handover configuration to instruct the user equipment to perform a handover or conditional handover to the first target cell associated with the target centralization unit.

8. The apparatus of claim 7, wherein the RRC message includes an incremental configuration, the incremental configuration including one or more updated parameters for the handover from the user equipment to the first target cell, the one or more updated parameters referencing a known full configuration of the user equipment, wherein the full configuration corresponds to the configuration of the serving cell.

9. The apparatus of claim 7, wherein the RRC message includes an incremental configuration, the incremental configuration including one or more updated parameters for the handover from the user equipment to the first target cell, the one or more updated parameters referencing a known full configuration of the user equipment, wherein the full configuration corresponds to the configuration of the second target cell.

10. The apparatus of claim 9, wherein after the user equipment performs the handover from the serving cell to the second target cell, the user equipment uses the incremental configuration for the handover to the first target cell.

11. The apparatus according to any one of claims 1 to 10, wherein the LTM switching configuration includes one or more of the following values ​​or updated values ​​for switching of the user equipment: a trigger time value, an increment value, or a threshold value.

12. The apparatus according to any one of claims 1 to 11, wherein the relaxed handover requirement for the LTM handover configuration of the user equipment is more easily satisfied compared to the non-relaxed handover requirement, so as to more easily trigger the LTM handover to the second target cell based on the L1 measurement report, or the relaxed handover requirement for the LTM handover configuration triggers the LTM handover of the user equipment to the second target cell based on a wider range of L1 measurements compared to the non-relaxed handover requirement.

13. The apparatus according to any one of claims 1 to 12, wherein the LTM switching configuration is user-specific to the device.

14. The apparatus according to any one of claims 1 to 13, wherein the apparatus is configured to: Based on the L3 measurement report received by the source unit, it is detected that the user equipment is under radio conditions below a predetermined threshold relative to the serving cell; and The source centralization unit sends the LTM handover configuration for the second target cell to the source distribution unit based on the detection.

15. The apparatus according to any one of claims 1 to 14, wherein the apparatus is configured to: Based on the L3 measurement report received by the source concentration unit, it is detected that the user equipment is under radio conditions below a predetermined threshold relative to the serving cell; The source centralization unit confirms that it has not yet received an instruction for the user equipment to perform an LTM handover from the serving cell to the second target cell; as well as The source centralization unit sends the LTM handover configuration for the second target cell to the source distribution unit based on the detection and the confirmation.

16. The apparatus of any one of claims 1 to 15, wherein the LTM handover configuration for the LTM handover from the user equipment to the second target cell is an intermediate step handover or a transitional step handover, in order to reduce the likelihood of radio link failure of the user equipment before the user equipment performs a handover to the first target cell based on the handover configuration for the first target cell.

17. A method comprising: The Layer 3 measurement report is received from the user equipment by the source centralization unit via the source distribution unit. The Layer 3 measurement report provides the results of radio signal measurements of at least one cell. The source centralization unit determines, based on the Layer 3 measurement report, that a handover should be performed for the user equipment from the serving cell associated with the source centralization unit to a first target cell associated with the target centralization unit, wherein the handover configuration for the handover from the user equipment to the first target cell has not yet been prepared, and wherein the target centralization unit is different from the source centralization unit; The source centralization unit determines, based on the received Layer 3 measurement report, a Layer 1 / Layer 2 triggered mobility LTM LTM handover configuration to the source distribution unit associated with the serving cell, the LTM handover configuration having lenient handover requirements for LTM handover from the user equipment to a second target cell, wherein the second target cell is also associated with the source centralization unit. The source centralization unit sends the LTM handover configuration for the second target cell to the source distribution unit; as well as The source centralization unit sends a handover request to the target centralization unit associated with the first target cell to prepare a handover configuration for the user equipment to perform a handover to the first target cell.

18. An apparatus comprising: At least one processor; as well as At least one memory stores instructions that, when executed by the at least one processor, cause the device to at least: The source distribution unit associated with the serving cell receives a Layer 1 / Layer 2 triggered mobility LTM LTM handover configuration and a timer value from the source central unit. The LTM handover configuration has lenient handover requirements for LTM handover from user equipment to the target cell. The timer value is used for the LTM handover configuration to be used as an validity timer, wherein the target cell is associated with the source central unit and with a different distribution unit. The source distribution unit initiates a validity timer for the LTM handover configuration, the validity timer indicating a validity period for the LTM handover configuration; The source distribution unit receives a Layer 1 measurement report from the user equipment before the expiration of the validity timer used for the LTM handover configuration; The source distribution unit determines, based on the Layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met; as well as The source distribution unit sends a Medium Access Control (MAC) control element (MAC CE) to the user equipment to trigger the user equipment to perform an LTM handover to the target cell.

19. The apparatus of claim 18, wherein the target cell includes a second target cell, and wherein a handover configuration for the user equipment has been prepared for a handover to a first target cell associated with a target centralization unit, wherein the LTM handover configuration for the LTM handover from the user equipment to the second target cell is an intermediate step handover or a transitional step handover to reduce the likelihood of radio link failure of the user equipment before the user equipment performs a handover to the first target cell based on the handover configuration for the first target cell.

20. A method comprising: The source distribution unit associated with the serving cell receives a layer 1 / layer 2 triggered mobility LTMLTM handover configuration and a timer value from the source central unit. The LTM handover configuration has lenient handover requirements for LTM handover from user equipment to the target cell. The timer value is used for the LTM handover configuration to be used as an validity timer, wherein the target cell is associated with the source central unit and with a different distribution unit. The source distribution unit initiates a validity timer for the LTM handover configuration, the validity timer indicating a validity period for the LTM handover configuration; The source distribution unit receives a Layer 1 measurement report from the user equipment before the expiration of the validity timer used for the LTM handover configuration; The source distribution unit determines, based on the Layer 1 measurement report, that the lenient handover requirements of the LTM handover configuration have been met; as well as The source distribution unit sends a Medium Access Control (MAC) element to the user equipment to trigger the user equipment to perform an LTM handover to the target cell.

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