Base station

Abstract

This base station is provided with a central device. The central device is provided with: a transmitting / receiving unit for transmitting, to another base station, a message related to mobility in lower layer control for causing a terminal that connects to a first cell controlled by the base station to transition to a second cell controlled by the other base station; and a control unit for including, in the message, an information element requiring the mobility which maintains the connection between the terminal and the central device. The control unit generates, with respect to the other base station, a confirmation message for confirming whether the other base station can support the mobility which maintains the connection between the terminal and the central device, and the transmitting / receiving unit transmits the confirmation message, before transmitting the message, to the other base station.

Description

base station

[0001] The present disclosure relates to a base station that performs Inter-CU LTM.

[0002] The 3rd Generation Partnership Project (3GPP (registered trademark)) has specified the 5th generation mobile communication system (5G, also known as New Radio (NR) or Next Generation (NG)), and is also working on specifications for next-generation mobile communication systems called Beyond 5G, 5G Evolution, or 6G.

[0003] 3GPP Release 19 discusses Lower Layer Triggered Mobility (LTM), which triggers a handover (HO) in which a terminal changes cells at a lower layer. Specifically, as an extension of Intra-CU LTM, which performs LTM between multiple cells controlled by a Central Unit (CU) of a base station, Inter-CU LTM, which performs LTM for a cell controlled by a CU of another base station, is being discussed. Note that the word "cell" may be interpreted as a Distributed Unit (DU) of the base station.

[0004] Inter-CU LTM is a mechanism that combines conventional HO with Intra-CU LTM. In other words, in Inter-CU LTM, not only the cell to which the terminal connects but also the CU connected via that cell changes. This type of Inter-CU LTM is called Inter-CU LTM with PDCP reset because it switches the connection with the CU at the PDCP layer.

[0005] On the other hand, in Inter-CU LTM, in order to reduce communication interruptions that occur when changing a CU, it has been proposed to change the cell to which a terminal connects without changing the CU to which the terminal connects. This type of Inter-CU LTM is called Inter-CU LTM without PDCP reset because it does not switch the connection with the CU in the PDCP layer (Non-Patent Document 1).

[0006] “Inter-gNB LTM and keep PDCP anchor”, R3-243522, 3GPP TSG-RAN WG3 #124, 3GPP, May 20-24, 2024

[0007] A base station (source base station) requesting an Inter-CU LTM must notify a base station (target base station) requesting an Inter-CU LTM of whether or not a PDCP reset has occurred in the Inter-CU LTM.

[0008] However, there are cases where the target base station does not support Inter-CU LTM without PDCP reset in the first place, and in such cases, the request for Inter-CU LTM without PDCP reset may end in failure.

[0009] Therefore, an object of the present disclosure is to provide a base station that can check with a target base station whether it supports Inter-CU LTM with PDCP reset.

[0010] One aspect of the disclosure is a base station including a central device, the central device including: a transceiver unit (radio signal transceiver unit 110) that transmits to another base station a message related to lower layer controlled mobility that transitions a terminal connected to a first cell controlled by the base station to a second cell controlled by the other base station; and a control unit (control unit 170) that includes in the message an information element requesting the mobility that maintains the connection between the terminal and the central device, the control unit generating a confirmation message for the other base station to confirm whether the other base station can support the mobility that maintains the connection between the terminal and the central device, and the transceiver unit transmitting the confirmation message to the other base station before transmitting the message.

[0011] FIG. 1 is a diagram showing an overall schematic configuration of a wireless communication system. FIG. 2 is a diagram showing frequency ranges used in the wireless communication system. FIG. 3 is a diagram showing example configurations of radio frames, subframes, slots, and symbols used in the wireless communication system. FIG. 4 is a functional block diagram of a base station. FIG. 5 is a functional block diagram of a terminal. FIG. 6 is a sequence diagram of Inter-CU LTM without PDCP reset (Enhanced LTM). FIG. 7 is an example of an IE indicating an indication of Enhanced LTM. FIG. 8 is an example of an IE indicating lower layer configuration. FIG. 9 is an example of an IE included in RRCReconfigComp Transfer. FIG. 10 is an example of an IE included in LTM Success Notification. FIG. 11 is a sequence diagram showing the first half of the overall operation in Enhanced LTM, focusing on the user plane. FIG. 12 is a sequence diagram showing the second half of the overall operation in Enhanced LTM, focusing on the user plane. FIG. 13 is a sequence diagram focusing on the operation of a source CU-CP managing bearer context in Enhanced LTM. Fig. 14 is a sequence diagram showing the first half of the overall operation in Enhanced LTM, focusing on the user plane. Fig. 15 is a sequence diagram showing the second half of the overall operation in Enhanced LTM, focusing on the user plane. Fig. 16 is a sequence diagram focusing on the operation of the target CU-CP managing the bearer context in Enhanced LTM. Fig. 17 is an example of an IE included in an HO Request. Fig. 18 is an example of an IE included in an HO Request Ack. Fig. 19 is an example of an IE indicating a UE ID, included in an HO Request. Fig. 20 is an example of an IE indicating a UE ID, included in a Bearer Context Setup / Modification Request. Fig. 21 is a diagram showing the relationship between gNB capabilities requested in Enhanced LTM and the components of the gNB (CU-CP, CU-UP, DU).Fig. 22 is a schematic sequence diagram showing an Xn Setup procedure related to reporting of gNB capability. Fig. 23 is a detailed sequence diagram showing an Xn Setup procedure related to reporting of gNB capability. Fig. 24 is an example of an IE included in an Xn Setup Request. Fig. 25 is an example of an IE included in an Xn Setup Response. Fig. 26 is an example of an IE included in a gNB-CU-CP Configuration Update. Fig. 27 is an example of an IE included in a gNB-CU Configuration Update. Fig. 28 is a diagram showing an example of the hardware configuration of a base station and a terminal. Fig. 29 is a diagram showing an example of the configuration of a vehicle.

[0012] Hereinafter, embodiments will be described with reference to the drawings. Note that the same or similar reference numerals are used to designate the same functions or configurations, and descriptions thereof will be omitted as appropriate.

[0013] (1) Configuration of Wireless Communication System The wireless communication system 10 shown in Fig. 1 is a wireless communication system conforming to a method called 5G. Alternatively, the wireless communication system 10 may be a wireless communication system conforming to a method called Beyond 5G, 5G Evolution, or 6G.

[0014] The wireless communication system 10 can support Massive Multiple-Input Multiple-Output (Massive MIMO), which generates more directional beams by controlling wireless signals transmitted from multiple antenna elements, Carrier Aggregation (CA), which uses multiple component carriers (CCs) as a bundle, and Dual Connectivity (DC), which enables simultaneous communication with two base stations.

[0015] 1 , the wireless communication system 10 includes a base station 100 (hereinafter also referred to as a gNodeB (gNB) 100) constituting a Next Generation-Radio Access Network (NG-RAN) 20, and a terminal 200 (hereinafter also referred to as a user equipment (UE) 200) that performs wireless communication with the gNB 100. The NG-RAN 20 may be read as the gNB 100.

[0016] The NG-RAN 20 is connected to a core network (CN) 30. The CN 30 is composed of multiple network functions (NFs). The NFs are, for example, an Access and Mobility Management Function (AMF) 300 and a Network Data Analytics Function (NWDAF) 400. The AMF 300 performs, for example, registration of the UE 200. The NWDAF 400 performs, for example, optimization of the CN 30. Note that the specific configuration of the wireless communication system 10, for example, the number of gNBs 100 and UEs 200, is not limited to the example shown in FIG. 1 . The NG-RAN 20 and the CN 30 may be simply referred to as a "network (NW)."

[0017] The gNB100 may be divided into a central unit (CU) that is connected to the network and controls the connection with the UE200, and a distributed unit (DU) that is connected to the UE200. The CU may be divided into a CU-CP that controls the control plane (CP) and a CU-UP that controls the user plane (UP). That is, the gNB100 may be divided into a CU-CP, a CU-UP, and a DU. In this specification, the following terms are understood to mean the same thing and may be read interchangeably: CU / CU-CP and gNB DU and a cell (formed by the DU)

[0018] 2, the wireless communication system 10 may support multiple frequency ranges (FR), namely, the following FRs: FR1: 410 MHz to 7.125 GHz FR2-1: 24.25 GHz to 52.6 GHz FR2-2: Over 52.6 GHz to 71 GHz

[0019] In FR1, a subcarrier spacing (SCS) of 15, 30, or 60 kHz and a bandwidth (BW) of 5 to 100 MHz may be used, while in FR2-1, an SCS of 60 or 120 kHz (or even 240 kHz) and a BW of 50 to 400 MHz may be used.

[0020] In FR2-2, Cyclic Prefix-Orthogonal Frequency Division Multiplexing (CP-OFDM) or Discrete Fourier Transform-Spread-Orthogonal Frequency Division Multiplexing (DFT-S-OFDM) with a larger SCS may be used to avoid increased phase noise.

[0021] As shown in Fig. 3, one slot in the wireless communication system 10 consists of 14 symbols. If this configuration is maintained, the larger (wider) the SCS, the shorter the symbol period (and slot period). Note that the SCS is not limited to the frequency shown in Fig. 3 and may be, for example, 480 kHz, 960 kHz, or other frequencies.

[0022] Furthermore, the number of symbols constituting one slot does not necessarily have to be 14, but may be, for example, 28 or 56. Furthermore, the number of slots per subframe may differ depending on the SCS.

[0023] (2) Functional block configuration of wireless communication system (2.1) Functional block configuration of base station As shown in Figure 4, the gNB 100 includes a wireless signal transceiver unit 110, an amplifier unit 120, a modulation / demodulation unit 130, a control signal / reference signal processing unit 140, an encoding / decoding unit 150, a data transceiver unit 160, and a control unit 170.

[0024] The gNB100 of the embodiment may be interpreted as a concept including a source base station (gNB100A) that controls the cell from which UE200 transitions when HO or LTM is executed, and target base stations (gNB100B, gNB100C) that control the cell to which UE200 transitions.

[0025] The gNB100 of the embodiment may include a central unit (CU) connected to a network and controlling a connection with the UE200, and a distributed unit (DU) connected to the UE200. The CU may include a CU-CP that controls a control plane (CP) and a CU-UP that controls a user plane (UP). That is, the gNB100 may include a CU-CP, a CU-UP, and a DU.

[0026] As described above, the gNB 100 of the embodiment may be interpreted as a CU (or a CU-CP). That is, the CU (or the CU-CP) may be understood to include a radio signal transceiver 110, an amplifier 120, a modem 130, a control signal / reference signal processor 140, an encoder / decoder 150, a data transceiver 160, and a controller 170.

[0027] The radio signal transmitting / receiving unit 110 transmits and receives radio signals to and from the UE 200. The radio signal transmitting / receiving unit 110 may be configured with a transmitting unit that transmits radio signals to the UE 200 and a receiving unit that receives radio signals from the UE 200. The radio signals may include data or may be interpreted as data. Transmission may be interpreted as configuration, instruction, notification, etc. Reception may be interpreted as (reported), notification, etc. Note that configuration may be realized by configuration information (information element (IE)) of a radio resource control (RRC) layer, and instruction may be realized by a control element (CE) or downlink control information (DCI) of a medium access control (MAC) layer.

[0028] The radio signal transceiver 110 of the embodiment can receive a message related to lower layer controlled mobility from another gNB100 (gNB100A) for transitioning a UE200 connected to a first cell controlled by the other gNB100 (gNB100A) to a second cell controlled by the gNB100 (gNB100B or gNB100C). The lower layer controlled mobility may be interpreted as corresponding to the LTM described above. This message is, for example, a request message requesting an LTM from the gNB100 (gNB100B or gNB100C). Note that the first cell may be interpreted as a DU (i.e., a source DU) included in the other gNB100 (gNB100A). Similarly, the second cell may be interpreted as a DU (i.e., a target DU) included in the gNB100 (gNB100B or gNB100C).

[0029] The radio signal transceiver 110 of the embodiment can transmit a response message to the message related to the above-mentioned LTM to another gNB100 (gNB100A). This response message is, for example, an authorization message that authorizes the LTM requested by the other gNB100 (gNB100A). In addition, the radio signal transceiver 110 of the embodiment may receive lower layer configuration information generated by a DU constituting the gNB100 (gNB100B or gNB100C) from the DU. Note that the lower layer configuration information (lower layer configuration) will be described later.

[0030] The radio signal transceiver 110 of the embodiment can receive a completion message indicating completion of LTM from the UE 200 and transmit this completion message to another gNB 100 (gNB100A). That is, the radio signal transceiver 110 can forward the completion message received from the UE 200 to the other gNB 100 (gNB100A). Furthermore, the radio signal transceiver 110 can receive, from the other gNB 100 (gNB100A), the contents of the completion message decoded by the other gNB 100 (gNB100A).

[0031] The radio signal transceiver 110 of the embodiment can transmit, to another gNB100 (gNB100B or gNB100C), a message related to lower layer controlled mobility that causes a UE200 connected to a first cell controlled by the gNB100 (gNB100A) to transition to a second cell controlled by the other gNB100 (gNB100B or gNB100C). The lower layer controlled mobility may be interpreted as corresponding to the above-mentioned LTM. Note that the first cell may be replaced with a DU (i.e., a source DU) included in the other gNB100 (gNB100A). Similarly, the second cell may be replaced with a DU (i.e., a target DU) included in the gNB100 (gNB100B or gNB100C).

[0032] The radio signal transceiver 110 of the embodiment can transmit a confirmation message to the other gNB100 (gNB100B or gNB100C) to confirm whether the other gNB100 (gNB100B or gNB100C) supports Inter-CU LTM without PDCP reset (Enhanced LTM) before transmitting the message related to the LTM described above to the other gNB100. The confirmation message may include an information element to confirm whether an interface can be established between a CU-UP (which may be referred to as a second control unit) included in the gNB100 (gNB100A) and the other gNB100 (gNB100B or gNB100C). The confirmation message may also include an information element to confirm whether a bearer can be established between a CU-CP (which may be referred to as a first control unit) included in the gNB100 (gNB100A) and a DU constituting the other gNB100 (gNB100B or gNB100C). Inter-CU LTM without PDCP reset (Enhanced LTM) will be described later.

[0033] The radio signal transceiver 110 of the embodiment can receive, from the other gNB100 (gNB100B or gNB100C), capability information of the other gNB100 (gNB100B or gNB100C) indicating whether the above-mentioned support is available. Furthermore, the radio signal transceiver 110 can receive, from the other gNB100 (gNB100B or gNB100C), capability information of the other gNB100 (gNB100B or gNB100C) indicating whether the above-mentioned interface can be established. Furthermore, the radio signal transceiver 110 can receive, from the other gNB100 (gNB100B or gNB100C), capability information of the other gNB100 (gNB100B or gNB100C) indicating whether the above-mentioned bearer can be established. Note that the gNB capability information may be referred to as a gNB capability.

[0034] The amplifier unit 120 is configured by a power amplifier (PA) / low noise amplifier (LNA), etc. The amplifier unit 120 amplifies the radio signal output from the radio signal transmitting / receiving unit 110. The amplifier unit 120 also amplifies the radio signal output from the modulation / demodulation unit 130.

[0035] The modem unit 130 performs data modulation / demodulation, transmission power setting, resource block allocation, etc. for each predetermined communication destination (UE 200 or another UE 200). CP-OFDM / DFT-S-OFDM may be applied to the modem unit 130. Furthermore, DFT-S-OFDM may be used not only for the uplink (UL) but also for the downlink (DL).

[0036] The control signal and reference signal processor 140 performs processing related to control signals transmitted and received between the UE 200, such as radio resource control (RRC) signaling.

[0037] The control signal / reference signal processing unit 140 performs processing related to reference signals transmitted and received between the UE 200, such as a Demodulation Reference Signal (DMRS), a Phase Tracking Reference Signal (PTRS), a Channel State Information-Reference Signal (CSI-RS), a Sounding Reference Signal (SRS), and a Positioning Reference Signal (PRS).

[0038] The channels include control channels and data channels. The control channels include a physical uplink control channel (PUCCH), a physical downlink control channel (PDCCH), a physical random access channel (PRACH), a physical broadcast channel (PBCH), etc. The data channels include a physical uplink shared channel (PUSCH), a physical downlink shared channel (PDSCH), etc.

[0039] The encoding / decoding unit 150 performs division / concatenation and coding / decoding of data included in a radio signal for each predetermined communication destination (UE 200 or another UE 200).

[0040] Specifically, the encoding / decoding unit 150 decodes the data output from the modem unit 130 and concatenates the decoded data. In addition, the encoding / decoding unit 150 divides the data output from the data transmitter / receiver 160 into pieces of a predetermined size and performs coding on the divided data.

[0041] The data transmitter / receiver 160 assembles and disassembles data units (Protocol Data Units (PDUs) / Service Data Units (SDUs)) that make up data between each layer. The multiple layers include a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and a Packet Data Convergence Protocol (PDCP) layer. The data transmitter / receiver 160 also performs data error correction and retransmission control based on Hybrid Automatic Repeat Request (HARQ).

[0042] The control unit 170 controls the gNB 100. The control unit 170 controls, for example, transmission and reception of radio signals by the radio signal transceiver unit 110, amplification by the amplifier unit 120, data modulation / demodulation by the modem unit 130, signal processing by the control signal and reference signal processor 140, coding / decoding by the encoder / decoder unit 150, and assembly / disassembly of data units by the data transceiver unit 160.

[0043] The control unit 170 can execute HO of the UE 200 and LTM that triggers the HO in a lower layer. HO and LTM may be interpreted as transitioning the UE 200 between cells controlled by the gNB 100. Furthermore, an LTM that transitions the UE 200 between multiple cells controlled by the same gNB 100 (CU) may be referred to as an Intra-CU LTM, and an LTM that transitions the UE 200 to a cell controlled by a different gNB 100 (CU) may be referred to as an Inter-CU LTM. Note that HO and LTM may be interpreted as terms such as cell transition, cell change, and beam change.

[0044] The control unit 170 according to the embodiment can permit LTM that maintains a connection between the UE 200 and another central unit (CU) included in another gNB 100 (gNB100A) based on the message related to the LTM described above. Such an LTM may be referred to as Inter-CU LTM without PDCP reset (Enhanced LTM).

[0045] The control unit 170 of the embodiment can generate a response message to the message related to the LTM described above. The control unit 170 can include lower layer configuration information in this response message without including upper layer configuration information. Note that the upper layer configuration information may be called upper layer configuration (RRC configuration). Also, the lower layer configuration information may be called lower layer configuration.

[0046] Based on the message related to the LTM described above, the control unit 170 of the embodiment can permit an LTM that establishes a connection between the UE200 and a CU included in a gNB100 (gNB100B or gNB100C) instead of permitting an LTM that maintains a connection between the UE200 and another central unit (CU) included in another gNB100 (gNB100A). Such an LTM may be called an Inter-CU LTM with PDCP reset (Basic LTM).

[0047] The control unit 170 of the embodiment can perform LTM while maintaining a connection between UE200 and the central unit (CU) provided in gNB100 (gNB100A) based on a response message from another gNB100 (gNB100B or gNB100C) in response to the message related to the LTM described above.

[0048] The control unit 170 according to the embodiment can set a communication path (bearer context) of the UE 200 based on the bearer setting information for the second cell included in the response message. Note that the term "setting" here may be interpreted as meaning "changing" or "managing."

[0049] The control unit 170 of the embodiment can permit LTM that maintains the connection between the UE 200 and another central unit (CU) included in another gNB 100 (gNB 100B or gNB 100C) based on the message related to the LTM described above. Such an LTM may be called Inter-CU LTM without PDCP reset (Enhanced LTM).

[0050] The control unit 170 of the embodiment can generate a response message to the message related to the LTM described above. The control unit 170 can include lower layer configuration information in this response message without including upper layer configuration information. Note that the upper layer configuration information may be called upper layer configuration (RRC configuration). Also, the lower layer configuration information may be called lower layer configuration.

[0051] The control unit 170 of the embodiment may include a CU-CP (which may be referred to as a first control unit) that controls the control plane and a CU-UP (which may be referred to as a second control unit) that controls the user plane. In this case, the CU-CP can instruct the CU-UP to start data transmission from the CU-UP to the second cell before the LTM is completed. Furthermore, in this case, the CU-CP can instruct the CU-UP to end data transmission from the CU-UP to the first cell after the LTM is completed. Furthermore, the "CU-UP that controls the user plane" referred to here is not limited to a CU-UP (i.e., a source CU-UP) included in the gNB100 (gNB100A), but may also be another CU-UP (i.e., a target CU-UP) included in another gNB100 (gNB100B or gNB100C). In other words, these instructions may be interpreted as instructions from a CU-CP provided in a gNB100 (gNB100A) to another CU-UP provided in another gNB100 (gNB100B or gNB100C).

[0052] In the embodiment, the control unit 170 can include an information element requesting an LTM that maintains the connection between the UE 200 and the CU provided in the gNB 100 (gNB 100A) in the message related to the LTM described above.

[0053] In the embodiment, the control unit 170 can generate a confirmation message to another gNB100 (gNB100B or gNB100C) to confirm whether the other gNB100 (gNB100B or gNB100C) can support LTM that maintains a connection between the UE200 and the CU provided in the gNB100 (gNB100A).

[0054] (2.2) Functional Block Configuration of Terminal As shown in FIG. 5, the UE 200 includes a radio signal transmitting / receiving unit 210 and a control unit 220.

[0055] The radio signal transceiver 210 transmits and receives radio signals to and from the gNB 100. The radio signal transceiver 210 may be configured with a transmitter that transmits radio signals to the gNB 100 and a receiver that receives radio signals from the gNB 100. The radio signals may include data or may be interpreted as data. Transmission may be interpreted as report, notification, etc. Reception may be interpreted as (configured), (instructed), (notified), etc. Note that configuration may be realized by configuration information (information element (IE)) of the radio resource control (RRC) layer, and instruction may be realized by a control element (CE) or downlink control information (DCI) of the medium access control (MAC) layer.

[0056] The control unit 220 controls the UE 200. The control unit 220 controls, for example, the transmission and reception of radio signals by the radio signal transmission and reception unit 210.

[0057] (3) Operation of the wireless communication system (3.1) Problems Problems of the embodiment will be described. Note that the numbers of the problems may be interpreted as corresponding to the numbers of the operation examples, but this should not be interpreted as preventing the combination of the operation examples to solve the problems.

[0058] (3.1.1) Issue 1: There was room for optimizing the sequence between gNBs in Inter-CU LTM without PDCP reset (Enhanced LTM). In particular, there was much room for optimization in the behavior of the target gNB that received an Enhanced LTM request.

[0059] (3.1.2) Issue 2: Inter-CU LTM without PDCP reset (Enhanced LTM) had room for optimizing the sequence for managing the bearer context of UE 200. In addition, the sequence to be considered differed between when the source CU-CP manages the bearer context and when the target CU-CP manages the bearer context.

[0060] (3.1.3) Problem 3 Inter-CU LTM without PDCP reset (Enhanced LTM) may trigger Enhanced LTM preparation for a target gNB that does not support Enhanced LTM. In this case, the Enhanced LTM request may fail or be canceled.

[0061] (3.2) Operational Examples An operational example of the embodiment will be described. In each operational example described below, gNB100A is a source gNB that controls a source cell of UE200, and gNB100B and gNB100C are target gNBs that control destination cells of UE200. Furthermore, the CU-CP, CU-UP, and DU of gNB100A may be referred to as source CU-CP, source CU-UP, and source DU, respectively. Similarly, the CU-CP, CU-UP, and DU of gNB100B and gNB100C may be referred to as target CU-CP, target CU-UP, and target DU, respectively. Note that the term "target" may be interchangeable with the term "candidate." Furthermore, the term "establishment" may be interchangeable with the term "foundation." Furthermore, the term "Inter-CU LTM without PDCP reset" may be interchangeable with the term "Enhanced LTM." Similarly, the term Inter-CU LTM with PDCP reset may be read interchangeably with the term Basic LTM.

[0062] (3.2.1) Operation Example 1 Operation example 1 will be described with reference to Figures 6 to 10. Operation example 1 is the operation of a target gNB when an Inter-CU LTM without PDCP reset (Enhanced LTM) is requested from a source gNB, and also the operation of the source gNB corresponding to this.

[0063] 6 is a sequence diagram of Inter-CU LTM without PDCP reset (Enhanced LTM). In FIG. 6, the sequence before Cell Switch execution may be referred to as LTM preparation. First, the CU-CP (source CU-CP) of gNB100A, which has received an L3 measurement report from UE200, decides to execute LTM (LTM decision in the figure). Next, the source CU-CP transmits an HO Request requesting LTM to the CU-CPs (target CU-CPs) of gNB100B and gNB100C. This HO Request may include an indication of whether the LTM is the above-mentioned Enhanced LTM.

[0064] Fig. 7 shows an example of an IE indicating an Enhanced LTM indication. In Fig. 7, when the PDCP anchor keep indicator is true, it indicates Enhanced LTM, and when the PDCP anchor keep indicator is false, it indicates Inter-CU LTM with PDCP reset (Basic LTM). The Enhanced LTM indication may be included in the LTM configuration IE, or may be included for each candidate configuration or candidate cell in the LTM configuration list, or may be an independent IE.

[0065] The Enhanced LTM indication may be included not only in the HO Request shown in Fig. 6 but also in the following messages: HO Request Ack, SN Addition Request / SN Addition Request Ack, SN Modification Request / SN Modification Request Ack, SN Modification Required / SN Modification Confirm, SN Change Required / SN Change Confirm, Existing Xn message, New Xn message

[0066] Returning to Fig. 6, upon receiving the Enhanced LTM indication, the target CU-CP triggers LTM configuration for the subordinate DU (target DU). That is, the target CU-CP requests the target DU to configure lower layers. Furthermore, the target CU-CP receives the lower layer configuration generated by the target DU from the target DU (UE Context Setup in the figure).

[0067] Next, the target CU-CP sends an HO Request Ack to the source CU-CP, authorizing LTM. The target CU-CP includes the lower layer configuration received from the target DU in the HO Request Ack. Here, when the target CU-CP receives the above-mentioned Enhanced LTM indication, it does not need to include its own generated upper layer configuration (RRC Configuration) in the HO Request Ack. Note that when the target CU-CP receives the above-mentioned Basic LTM indication, it includes its own generated upper layer configuration (RRC Configuration) in the HO Request Ack.

[0068] The lower layer configuration may include the following IEs: DU to CU RRC Information (including CellGroupConfig) LTM Configuration

[0069] 8 shows an example of an IE indicating a lower layer configuration. The IE indicating the lower layer configuration may be included in an IE of the LTM configuration, may be included for each candidate configuration or candidate cell in the LTM configuration list, or may be an independent IE. Furthermore, the lower layer configuration may be included in an RRC container (Target NG-RAN node To Source NG-RAN node Transparent Container in the figure). In this case, LTMLowerLayerConfiguration as an inter-node RRC message may be defined in 3GPP TS 38.331 as an IE including CellGroupConfig for LTM.

[0070] The lower layer configuration may be included not only in the HO Request Ack shown in Fig. 6 but also in the following messages: SN Addition Request Ack, SN Modification Request Ack, SN Modification Required, SN Change Required / SN Change Confirm, an existing Xn message, and a new Xn message.

[0071] Returning to Fig. 6, upon receiving the HO Request Ack, the source CU-CP performs UE Context Modification with the DU, and then performs LTM Update with the target CU-CP. Finally, the source CU-CP transmits an RRCReconfiguration message to the UE 200. The RRCReconfiguration message may include information obtained by merging the above-described low layer configuration generated by the target DU and the upper layer configuration generated by the source CU-CP.

[0072] After transmitting the RRCReconfiguration message, the source CU-CP executes Inter-CU LTM without PDCP reset and changes the cell to which UE 200 connects (Cell Switch execution in the figure). After completing the cell change, UE 200 transmits RRCReconfigComplete (RRCReconfigComp in the figure) to the target CU-CP to notify that the cell change has been completed.

[0073] Here, in Inter-CU LTM without PDCP reset, UE 200 connects to the target DU while maintaining connection with the source CU-CP. Therefore, the target CU-CP cannot decode the RRCReconfigComplete received from UE 200. Therefore, the target CU-CP may transfer the RRCReconfigComplete to the source CU-CP (RRCReconfigComp Transfer in the figure).

[0074] Fig. 9 shows an example of an IE included in RRCReconfigComp Transfer. This IE may be included not only in RRCReconfigComp Transfer shown in Fig. 6 but also in the following messages: RRC Transfer Handover Success Existing Xn message New Xn message

[0075] 6 , the source CU-CP that has received the RRCReconfigComp Transfer may decode the contents and transmit them to the target CU-CP (LTM Success Notification in the figure). Furthermore, the target CU-CP may determine that the cell change of the UE 200 has been completed upon receiving the LTM Success Notification.

[0076] 10 shows an example of an IE included in the LTM Success Notification. This IE may be included in the LTM configuration IE, may be included for each candidate configuration or candidate cell in the LTM configuration list, or may be an independent IE. This IE may also be included in an RRC container. In this case, LTMRRCReconfigComp as an inter-node RRC message may be defined in 3GPP TS 38.331 as an IE including RRCReconfigurationComplete received from UE 200 after completion of LTM Cell Switch.

[0077] This IE may be included in the following messages as well as the LTM Success Notification shown in Fig. 6: Handover Success, an existing Xn message, and a new Xn message.

[0078] In the above description, it is assumed that the target gNB in ​​Operation Example 1 supports Enhanced LTM, but this is not limited to this. The target gNB in ​​Operation Example 1 does not have to support Enhanced LTM. When a target gNB that does not support Enhanced LTM receives an indication of Enhanced LTM, it may transmit to the source gNB that it can perform Basic LTM instead of rejecting the request for Enhanced LTM. In this case, the target gNB that does not support Enhanced LTM may perform preparation for Basic LTM.

[0079] (3.2.2) Operation Example 2 Operation example 2 will be described with reference to Figures 11 to 20. Operation example 2 is an operation for managing the communication path (bearer context) of UE200 between a source CU-UP and a target DU when executing Inter-CU LTM without PDCP reset (Enhanced LTM). Hereinafter, a case where the source CU-CP manages the bearer context between the source CU-UP and the target DU will be described as operation example 2-1, and a case where the target CU-CP manages the bearer context between the source CU-UP and the target DU will be described as operation example 2-2.

[0080] (3.2.2.1) Operation Example 2-1 Operation example 2-1 will be described with reference to Fig. 11 to Fig. 13. Fig. 11 to Fig. 13 are sequence diagrams focusing on user plane operations in Inter-CU LTM without PDCP reset (Enhanced LTM). The user plane operations may be understood as operations (Bearer Context Modification in the figures) that manage (change) the communication path (bearer context) of UE 200 between source CU-UP and target DU.

[0081] Figures 11 and 12 show the overall sequence of Enhanced LTM. Specifically, Figure 11 shows the sequence before Early Sync, and Figure 12 shows the sequence after Early Sync. Figure 13 shows a sequence focusing on the operation of the source CU-CP in Enhanced LTM (operation to change the bearer context of UE 200). Therefore, hereinafter, Figure 13 will be mainly referred to, and Figures 11 and 12 will be referred to only when necessary.

[0082] First, step 1 in Fig. 13 will be described. The following operations may be performed to establish a bearer between the source CU-UP and the target DU and realize DL / UL transmission and reception in the user plane: The source CU-CP sends an Xn message to the target CU-CP to request LTM preparation or LTM modification. The source CU-CP may include information about the bearer established in the source CU-UP in this Xn message (Handover Request, HO Request in the figure). The target CU-CP may use information about the bearer established in the source CU-UP when triggering LTM setup (requesting lower layer setup) for the subordinate DU (target DU) (UE Context Setup Request / Response, UE Context Setup in the figure). The target CU-CP may send information about the bearer established in the subordinate DU (target DU) to the source CU-CP in response to the Xn message (requesting LTM preparation or LTM modification) received from the source CU-CP. The information about the bearer may be DL / UL TNL information for each DU / target cell / UE (Handover Request Ack, HO Request Ack in the figure). The source CU-CP may send information about the bearer of the target DU received from the target CU-CP and information about the target CU-CP to the source CU-UP (Bearer Context Modification Request, Bearer Context Modification in the figure).

[0083] Next, step 2 in Fig. 13 will be described. Before the Cell Switch in the figure (before receiving the Cell Switch Notification in Fig. 12), the following operations may be performed to start the Early Data Transmission in Fig. 11: The source CU-CP may instruct the source CU-UP to start Early data transmission to the target DU (Bearer Context Modification in the figure).

[0084] Next, step 3 in Fig. 13 will be described. After the Cell Switch in the figure and before the LTM completion (after the Cell Switch Notification in Fig. 12 is received and before the RRCReconfigurationComplete (RRCReconfigComp) indicating the completion of the Cell Switch is received), the following operations may be performed to start the Early Data Transmission in Fig. 12: The source CU-CP may instruct the source CU-UP to start Early data transmission to the target DU (Bearer Context Modification in the figure).

[0085] Finally, step 4 in Fig. 13 will be described. After LTM completion in the figure (after receiving RRCReconfigurationComplete (RRCReconfigComp) indicating the completion of Cell Switch in Fig. 12), the following operations may be performed to notify the source CU-UP that data transmission from the source CU-UP to the source DU will be terminated and data transmission will be switched to the target DU. The source CU-CP may instruct the source CU-UP to switch user plane DL / UL transmission from the source DU to the target DU (Bearer Context Modification in the figure).

[0086] In addition, the instruction to the source CU-UP in steps 2-4 may be an instruction for each target gNB / each target DU / each target cell.

[0087] (3.2.2.2) Operation Example 2-2 Operation example 2-2 will be described with reference to Fig. 14 to Fig. 16. Fig. 14 to Fig. 16 are sequence diagrams focusing on user plane operations in Inter-CU LTM without PDCP reset (Enhanced LTM). The user plane operations may be understood as operations (Bearer Context Modification in the figures) that manage (change) the communication path (bearer context) of UE 200 between source CU-UP and target DU.

[0088] Figures 14 and 15 show the overall sequence of Enhanced LTM. Specifically, Figure 14 shows the sequence before Early Sync, and Figure 15 shows the sequence after Early Sync. Figures 14 and 15 differ from Figures 11 and 12 in that the entity that changes the bearer context of UE 200 is the target CU-CP, not the source CU-CP. Figure 16 shows a sequence that focuses on the operation of the target CU-CP in Enhanced LTM (the operation that changes the bearer context of UE 200). Therefore, hereinafter, Figure 16 will be mainly referred to, and Figures 14 and 15 will be referred to only when necessary.

[0089] First, step 1 in Fig. 16 will be described. The following operations may be performed to establish a bearer between a source CU-UP and a target DU and realize DL / UL transmission and reception in the user plane: The source CU-CP sends an Xn message to the target CU-CP to request LTM preparation or LTM modification. The source CU-CP may include information about the bearer established with the source CU-UP in this Xn message (Handover Request, HO Request in the figure). At this time, this Xn message may include the E1AP ID (gNB-CU-CP UE E1AP ID, gNB-CU-UP UE E1AP ID) or RAN UE ID assigned when the source CU-CP established the bearer context with the source CU-UP (corresponding to i) described below). This Xn message may also include an ID uniquely assigned to the UE between gNBs (corresponding to ii) described below). - When triggering LTM configuration (requesting lower layer configuration) for a subordinate DU (target DU), the target CU-CP may use information about the bearer established in the source CU-UP (UE Context Setup Request / Response, UE Context Setup in the figure). - The target CU-CP may send information about the target DU's bearer to the source CU-UP (Bearer Context Modification Request, Bearer Context Modification in the figure). At this time, in case i) below, the gNB-CU-UP UE E1AP ID received from the source CU-CP may be used. On the other hand, in case ii), the RAN UE ID received from the source CU-CP and the gNB-CU-CP UE E1AP ID assigned by the target CU-CP may be used.Note that i) and ii) assume the case where multiple CU-CP and CU-UP pairs assign E1AP IDs to the same UE. i): The E1AP ID (gNB-CU-UP UE E1AP ID) assigned by the CU-UP to the UE when the UE's bearer context was initially established with the CU-UP is also used when another target CU-CP sends a Bearer Context Modification. ii): The E1AP ID assigned by the CU-UP to the UE when the UE's bearer context was initially established with the CU-UP is not used, and a new E1AP ID (gNB-CU-CP UE E1AP ID, gNB-CU-UP UE E1AP ID) is assigned between another target CU-CP and the CU-UP. - The target CU-CP may send information about the bearers established by its subordinate DUs (target DUs) to the source CU-CP in response to an Xn message (LTM preparation or LTM modification request) received from the source CU-CP. The bearer information may be DL / UL TNL information for each DU / target cell / UE (Handover Request Ack, HO Request Ack in the figure). In this case, the bearer information may include the E1AP ID (gNB-CU-CP UE E1AP ID) assigned when the target CU-CP sends a Bearer Context Modification Request to the source CU-UP.

[0090] Next, step 2 in Fig. 16 will be described. Before the Cell Switch in the figure (before receiving the Cell Switch Notification in Fig. 15), the following operations may be performed to start the Early Data Transmission in Fig. 14: The target CU-CP may instruct the source CU-UP to start Early data transmission to the target DU (Bearer Context Modification in the figure).

[0091] Next, step 3 in Fig. 16 will be described. After the Cell Switch in the figure and before the LTM completion (after the Cell Switch Notification in Fig. 15 is received and before the RRCReconfigurationComplete (RRCReconfigComp) indicating the completion of the Cell Switch is received), the following operations may be performed to start the Early Data Transmission in Fig. 15: The target CU-CP may instruct the source CU-UP to start Early data transmission to the target DU (Bearer Context Modification in the figure).

[0092] Finally, step 4 in Fig. 16 will be described. After LTM completion in the figure (after receiving RRCReconfigurationComplete (RRCReconfigComp) indicating the completion of Cell Switch in Fig. 15), the following operations may be performed to notify the source CU-UP that data transmission from the source CU-UP to the source DU will be terminated and that data transmission will be switched to the target DU. The target CU-CP may instruct the source CU-UP to switch user plane DL / UL transmission from the source DU to the target DU (Bearer Context Modification in the figure).

[0093] Note that the instruction to the source CU-UP in steps 2-4 may be an instruction for each target gNB / each target DU / each target cell. Furthermore, in the above-mentioned case ii), the Establish Bearer Context in FIG. 16 may associate the bearer context with an ID (UE ID) uniquely assigned to the UE between gNBs. The UE ID may be an existing RNTI or an existing AMF UE NGAP ID. Furthermore, the UE ID may be other than the RNTI or NGAP ID system, and may be an existing or new ID that can uniquely identify the UE between RAN nodes.

[0094] (3.2.2.3) Examples of IE in Operation Example 2 Examples of IE in Operation Example 2 (Operation Example 2-1 and Operation Example 2-2) will be described with reference to FIGS.

[0095] FIG. 17 shows an example of an IE included in an HO Request. FIG. 18 shows an example of an IE included in an HO Request Ack. "9.2.1.XX" in FIGS. 17 and 18 may be an IE that contains information about the bearer context and is included in an E1AP message transmitted from the CU-CP to the CU-UP. The E1AP message may be a Bearer Context Setup Request / Response or a Bearer Context Modification Request / Response. "9.2.1.YY" in FIG. 18 may be an IE that contains information about the bearer context and is included in an F1AP message transmitted from the CU-CP to the DU. The F1AP message may be a UE Context Setup Request / Response or a UE Context Modification Request / Response.

[0096] Fig. 19 shows an example of an IE indicating a UE ID included in an HO Request. Fig. 20 shows an example of an IE indicating a UE ID included in a Bearer Context Setup / Modification Request. "9.2.3.XX" in Fig. 19 may be an ID (UE ID) that can uniquely identify a UE across gNBs. The UE ID may also be an existing RNTI. "9.3.1.YY" in Fig. 20 may be an ID (UE ID) that can uniquely identify a UE across gNBs. The UE ID may also be an existing RNTI or an existing AMF UE NGAP ID. The Bearer Context Setup Request may also include the gNB-CU-UP UE E1AP ID that was acquired during LTM preparation and assigned to the UE when the CU-CP established the bearer context.

[0097] (3.2.2.4) Examples of Messages in Operation Example 2 Examples of messages in operation example 2 (operation example 2-1 and operation example 2-2) will be described.

[0098] (Xn Message) The source CU-CP may send an Xn message to the target CU-CP to request LTM preparation or LTM modification. This Xn message may be a Handover Request. The source CU-CP may include information about the bearer established with the source CU-UP in the Xn message. The bearer information may be information included in a Response message when the source CU-CP performs Bearer Context Setup for the source CU-UP, or may be information exchanged when E1 Setup is performed between the source CU-UP and the source CU-CP.

[0099] The target CU-CP may transmit information about the bearer established in the subordinate DU (target DU) to the source CU-CP in response to the above-mentioned Xn message. This response message may be a Handover Request Ack. The bearer information may be information included in a Response message when the target CU-CP performs UE Context Setup for the target DU, or may be information exchanged when F1 Setup is performed between the target CU-CP and the target DU.

[0100] Information about these bearers may be included in an IE in the LTM configuration, may be included for each candidate configuration or candidate cell in a list of LTM configurations, or may be an independent IE.

[0101] Information about these bearers may be included in the following messages, not limited to Handover Request / Handover Request Ack: SN Addition Request / SN Addition Request Ack, SN Modification Request / SN Modification Request Ack, SN Modification Required / SN Modification Confirm, SN Change Required / SN Change Confirm, Existing Xn message, New Xn message

[0102] (E1 Message) The source CU-CP may send information about the bearer of the target DU received from the target CU-CP and information about the target CU-CP to the source CU-UP. This information may be included in a Bearer Context Modification Request. Furthermore, the target CU-CP may send information about the bearer of the subordinate DU (target DU) to the source CU-UP. This information may be included in a Bearer Context Modification Request.

[0103] The source CU-UP may transmit to the target CU-CP information about the bearer of the target DU received from the source CU-CP and information about the bearer it holds. Note that the information about the bearer it holds may be selected based on the information of the target CU-CP. This information may be included in Bearer Context Modification Required.

[0104] This information may be included in the following messages, not limited to Bearer Context Modification Request / Bearer Context Modification Required: Bearer Context Modification Response Bearer Context Modification Confirm Existing E1 message New E1 message

[0105] (3.2.3) Operation Example 3 Operation Example 3 will be described with reference to Figures 21 to 27. Operation Example 3 is an operation in which capabilities (gNB capability) are exchanged between gNBs before executing Inter-CU LTM without PDCP reset (Enhanced LTM).

[0106] (Contents of Capability) gNB capability may be defined as Conditions 1 to 6 shown below. FIG. 21 is a diagram showing the relationship between the gNB capability (Conditions 1 to 6) required in Enhanced LTM and the components of the gNB (CU-CP, CU-UP, DU). Reference numerals 1 to 6 in FIG. 21 correspond to Conditions 1 to 6. Note that the term "gNB capability" may be interchangeable with the terms "CU-CP / CU-UP / DU capability."

[0107] Condition 1: Whether the target CU-CP can establish an E1 interface with an adjacent or specific CU-UP 1a: This capability may be defined as a capability for any adjacent CU-UP without specifying the target CU-UP. 1b: This capability may be defined as a capability for a specific CU-UP.

[0108] Condition 2: Whether the target DU can establish a bearer with an adjacent or specific CU-UP 2a: This capability may be defined as a capability for any adjacent CU-UP without specifying the target CU-UP. 2b: This capability may be defined as a capability for a specific CU-UP.

[0109] Condition 3: When the target CU-CP receives an Enhanced LTM request from an adjacent CU-CP (source CU-CP), can it send only the lower layer configuration of the target DU to the source CU-CP?

[0110] Condition 4: Can the source CU-CP trigger Enhanced LTM?

[0111] Condition 5: Whether the source CU-UP can establish an E1 interface with an adjacent or specific CU-CP. 5a: This capability may be defined as a capability for any adjacent CU-CP without specifying the target CU-CP. 5b: This capability may be defined as a capability for a specific CU-CP.

[0112] Condition 6: Whether the source CU-UP can establish a bearer with a DU (target DU) under an adjacent or specific CU-CP 6a: This capability may not specify a target DU and may be defined as a capability for any DU (target DU) under an adjacent CU-CP 6b: This capability may be defined as a capability for a specific DU

[0113] (Capability reporting) The gNB capabilities of conditions 1 to 6 may be reported in the Xn procedure using any of the following methods. ・The source CU-CP may send information about the CU-UP it is using / connected to to the target CU-CP to learn the capabilities of 1b and 2b possessed by the target CU-CP. ・The source CU-CP may report its own capabilities of 1a, 2a, 3, 4, 5a, 5b, 6a, and 6b to the target CU-CP. In this case, capabilities may be defined / reported for each CU-UP or DU as necessary. ・The source CU-CP may request a report on whether the target CU-CP has capabilities of 1a, 1b, 2a, 2b, 3, 4, 5a, 5b, 6a, and 6b. In this case, the CU-UP or DU to which the capability is to be reported may be specified as necessary. The target CU-CP may determine whether the target DU has capability 2b based on the CU-UP information received from the source CU-CP. The target CU-CP may determine whether it has capability 1b based on the CU-UP information received from the source CU-CP. The target CU-CP may determine whether it has capability 5b based on the source CU-CP information. The target CU-CP may send the requested capability in response to a capability report request of 1a, 1b, 2a, 2b, 3, 4, 5a, 5b, 6a, or 6b received from the source CU-CP. In this case, the capability may be reported for each CU-UP or DU as necessary.

[0114] The gNB capabilities under conditions 1 to 6 may be reported in the E1 procedure using any of the following methods: ・The CU-CP may send information about specific neighboring CU-CPs and their subordinate DUs to the CU-UP to learn the 5b and 6b capabilities that the CU-UP has. ・The CU-CP may request a report on whether the CU-UP has the 5a, 5b, 6a, and 6b capabilities. At this time, the CU-CP or DU to which the capability report is to be sent may be specified as necessary. ・The CU-UP may determine whether it has the 5b and 6b capabilities based on the information about neighboring CU-CPs and their subordinate DUs received from the CU-CP. ・The CU-UP may send the requested capabilities in response to a request for reporting the 5a, 5b, 6a, and 6b capabilities received from the source CU-CP. At this time, the capabilities may be reported for each CU-UP or DU as necessary.

[0115] (Variations regarding capabilities) These gNB capabilities may be defined / requested / reported per gNB node, or per cell served by the gNB node. Furthermore, these gNB capabilities may be defined / requested / reported via an interface of an OAM or O-RAN node, rather than via an interface of an NG-RAN node. This interface may be the E2 / A1 interface or O1 interface specified in O-RAN.

[0116] 22 and 23 are sequence diagrams showing the Xn Setup procedure related to reporting of gNB capability. Note that the Xn Setup procedure may be replaced with the NG-RAN node Configuration Update procedure or an existing / new Xn procedure. Also, the gNB-CU-CP Configuration Update procedure in FIG. 23 may be replaced with the E1 Setup procedure or an existing / new E1 procedure. Similarly, the gNB-CU Configuration Update procedure may be replaced with the F1 Setup procedure or an existing / new F1 procedure.

[0117] The Xn SetUp Request in Figures 22 and 23 may include the following information: Presence or absence of capabilities 1a, 2a, 3, 4, 5a, and 6a possessed by the source gNB Report request for capabilities 1a, 1b, 2a, 2b, 3, 4, 5a, 5b, 6a, and 6b possessed by the target gNB Information on CU-UPs targeted by capabilities 1b and 5b Information on DUs targeted by capabilities 2b and 6b

[0118] 22 and 23 may include the following information: - Presence or absence of 2b capability in target DU (or each target DU, if multiple) - Presence or absence of 5b and 6b capabilities in target CU-UP (or each target CU-UP, if multiple) - Presence or absence of 1a, 1b, 2a, 3, 4, 5a, and 6a capabilities in target gNB

[0119] The gNB-CU-CP Configuration Update in Fig. 23 may include the following information: - Report request for capabilities 5a, 5b, 6a, and 6b - Information on the CU-UP that is the target of capability 5b - Information on the DU that is the target of capability 6b - Presence or absence of capabilities 5a, 5b, 6a, and 6b for target CU-UP (if multiple, for each target CU-UP)

[0120] The gNB-CU Configuration Update in Fig. 23 may include the following information: - Report request for capabilities 2a and 2b - Information on the DU that is the target of capability 2b - Presence or absence of capabilities 2a and 2b for target DU (if multiple, for each target DU)

[0121] Figure 24 is an example of an IE included in an Xn Setup Request. Figure 25 is an example of an IE included in an Xn Setup Response. "9.2.1.XX" in Figures 24 and 25 may be a gNB capability report request to a neighboring CU-CP. "9.2.1.YY" in Figures 24 and 25 may be a gNB capability report from a CU-UP. These IEs may include information on the CU-UP or DU to which the capability is connected.

[0122] Figure 26 is an example of IEs included in a gNB-CU-CP Configuration Update. Figure 27 is an example of IEs included in a gNB-CU Configuration Update. "9.3.2.XX" in Figures 26 and 27 may be a gNB capability report request sent from a CU-CP to a CU-UP or DU. "9.3.2.YY" in Figures 26 and 27 may be a gNB capability report sent from a CU-UP or DU to a CU-CP. These IEs may include information on the CU-UP or DU that is the connection target of the capability.

[0123] (4) Actions and Effects According to the above-described embodiment, it is possible not only to notify Inter-CU LTM without PDCP reset but also to realize a sequence between gNBs 100 that is optimized for Inter-CU LTM without PDCP reset. In particular, it is possible to optimize the operation of the target gNB.

[0124] According to the above-described embodiment, it is possible not only to notify Inter-CU LTM without PDCP reset but also to realize bearer context management of UE 200 that is optimized for Inter-CU LTM without PDCP reset. In particular, even when entities that manage the bearer context are different, it is possible to optimize the sequence for managing the bearer context depending on each case.

[0125] According to the above-described embodiment, before notifying Inter-CU LTM without PDCP reset, gNBs can exchange their capabilities (gNB capability). This reduces the risk that Enhanced LTM preparation will be triggered for a target gNB that does not support Enhanced LTM, resulting in a failed / cancelled Enhanced LTM request.

[0126] (5) Other Embodiments The contents of the present invention have been described above in accordance with the embodiments, but it will be obvious to those skilled in the art that the present invention is not limited to these descriptions and that various modifications and improvements are possible.

[0127] The above-described operation examples may be combined and applied in a composite manner, as long as no contradiction occurs.

[0128] The block diagrams used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of hardware and / or software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are directly or indirectly connected (e.g., wired, wireless, etc.) and these multiple devices. The functional block may also be realized by combining software with the single device or multiple devices.

[0129] Functions include, but are not limited to, judgment, determination, judgment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how these functions are implemented.

[0130] For example, the base station 100, the terminal 200, etc. according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 28 is a diagram illustrating an example of the hardware configuration of the base station 100 and the terminal 200 according to an embodiment of the present disclosure. The base station 100 and the terminal 200 described above may be physically configured as a computer device including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0131] In the following description, the term "apparatus" can be interpreted as a circuit, a device, a unit, etc. The hardware configuration of base station 100 and terminal 200 may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0132] Each function in the base station 100 and the terminal 200 is realized by loading predetermined software (programs) onto hardware such as the processor 1001 and the memory 1002, causing the processor 1001 to perform calculations, control communication by the communication device 1004, and control at least one of reading and writing data in the memory 1002 and the storage 1003.

[0133] The processor 1001 controls the entire computer by running, for example, an operating system, and may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc.

[0134] The processor 1001 also reads programs (program codes), software modules, data, etc. from at least one of the storage 1003 and the communication device 1004 into the memory 1002 and executes various processes in accordance with these. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. While the above-described various processes have been described as being executed by one processor 1001, they may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may be transmitted from a network via a telecommunications line.

[0135] The memory 1002 is a computer-readable recording medium and may be configured by, for example, at least one of a read-only memory (ROM), an erasable programmable ROM (EPROM), an electrically erasable programmable ROM (EEPROM), a random access memory (RAM), etc. The memory 1002 may also be called a register, a cache, a main memory (primary storage device), etc. The memory 1002 can store executable programs (program codes), software modules, etc. for implementing a wireless communication method according to one embodiment of the present disclosure.

[0136] Storage 1003 is a computer-readable recording medium and may be, for example, at least one of an optical disk such as a Compact Disc ROM (CD-ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray disc), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy disk, a magnetic strip, etc. Storage 1003 may also be referred to as an auxiliary storage device. The above-mentioned storage medium may be, for example, a database, a server, or other suitable medium including at least one of memory 1002 and storage 1003.

[0137] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize, for example, at least one of Frequency Division Duplex (FDD) and Time Division Duplex (TDD).

[0138] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0139] Furthermore, each device, such as the processor 1001 and the memory 1002, is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0140] Furthermore, base station 100 and terminal 200 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, processor 1001 may be implemented using at least one of these pieces of hardware.

[0141] The notification of information is not limited to the aspects / embodiments described in the present disclosure and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling), broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0142] Each aspect / embodiment described in this disclosure may apply to at least one of a system using Long Term Evolution (LTE), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, a 4th generation mobile communication system (4G), a 5th generation mobile communication system (5G), a 6th generation mobile communication system (6G), an xth generation mobile communication system (xG) (where x is, for example, an integer or a decimal), Future Radio Access (FRA), New Radio (NR), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, Ultra-WideBand (UWB), Bluetooth (registered trademark), or any other suitable system, and next generation systems extended, modified, created, or defined based on these. In addition, multiple systems may be applied in combination (for example, a combination of at least one of LTE and LTE-A with 5G).

[0143] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described in this disclosure may be changed unless it is consistent. For example, the methods described in this disclosure present elements of various steps using an example order, and are not limited to the particular order presented.

[0144] In the present disclosure, a specific operation described as being performed by a base station may be performed by its upper node in some cases. In a network consisting of one or more network nodes having a base station, it is clear that various operations performed for communication with a terminal may be performed by at least one of the base station and another network node other than the base station (for example, an MME or an S-GW, etc., but are not limited to these). Although the above example illustrates a case where there is one other network node other than the base station, a combination of multiple other network nodes (for example, an MME and an S-GW) may also be used.

[0145] Information, signals (information, etc.) may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input / output via multiple network nodes.

[0146] Input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. Input and output information may be overwritten, updated, or added to. Output information may be deleted. Input information may be transmitted to another device.

[0147] The determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0148] The aspects / embodiments described in this disclosure may be used alone, in combination, or switched depending on the implementation. Notification of predetermined information (e.g., notification that "X is true") is not limited to explicit notification, but may be implicit (e.g., not notifying the predetermined information).

[0149] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0150] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0151] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0152] Note that terms described in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0153] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0154] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, may be expressed using relative values ​​from a predetermined value, or may be expressed using other corresponding information. For example, a radio resource may be indicated by an index.

[0155] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0156] In this disclosure, terms such as "base station (BS)," "radio base station," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. Base stations may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0157] A base station can accommodate one or more (e.g., three) cells (also called sectors). When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be divided into multiple smaller areas, and each smaller area can be provided with communication services by a base station subsystem (e.g., a small indoor base station (Remote Radio Head, RRH)). The term "cell" or "sector" refers to a part or the entire coverage area of ​​a base station and / or a base station subsystem that provides communication services within this coverage.

[0158] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0159] In this disclosure, terms such as "terminal," "user terminal," "Mobile Station (MS)," and "User Equipment (UE)" may be used interchangeably.

[0160] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0161] At least one of the base station and the mobile station may be referred to as a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a mobile object, the mobile object itself, etc. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. The mobile object may also be an autonomous mobile object operating based on an operational command. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an Internet of Things (IoT) device such as a sensor.

[0162] Furthermore, the base station in the present disclosure may be read as a terminal. For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a terminal is replaced with communication between multiple terminals (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the terminal 200 may be configured to have the functions of the base station 100 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to communication between terminals (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel.

[0163] Similarly, the term "terminal" in the present disclosure may be read as "base station." In this case, the base station 100 may be configured to have the functions of the terminal 200 described above.

[0164] 29 shows an example of the configuration of a vehicle 2001. As shown in Fig. 29, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, left and right front wheels 2007, left and right rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013.

[0165] The drive unit 2002 is composed of, for example, an engine, a motor, or a hybrid of an engine and a motor.

[0166] The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user.

[0167] The electronic control unit 2010 is composed of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals are input to the electronic control unit 2010 from various sensors 2021 to 2027 provided in the vehicle. The electronic control unit 2010 may also be called an Electronic Control Unit (ECU).

[0168] The signals from the various sensors 2021 to 2029 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0169] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs for controlling these devices. The information service unit 2012 uses information acquired from external devices via the communication module 2013, etc., to provide various types of multimedia information and multimedia services to the occupants of the vehicle 2001.

[0170] The information service unit 2012 may include input devices (e.g., keyboards, mice, microphones, switches, buttons, sensors, touch panels, etc.) that accept input from the outside, and may also include output devices (e.g., displays, speakers, LED lamps, touch panels, etc.) that output to the outside.

[0171] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driver's driving burden, such as millimeter-wave radar, Light Detection and Ranging (LiDAR), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., inertial measurement units (IMUs), inertial navigation systems (INSs), etc.), artificial intelligence (AI) chips, and AI processors, as well as one or more ECUs that control these devices. The driving assistance system unit 2030 also transmits and receives various information via the communication module 2013 to realize driving assistance functions or autonomous driving functions.

[0172] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, left and right front wheels 2007, left and right rear wheels 2008, axle 2009, microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 2029, which are provided in the vehicle 2001.

[0173] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a mobile station, or the like.

[0174] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021 to 2029 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012 to an external device via wireless communication. The electronic control unit 2010, the various sensors 2021 to 2029, the information service unit 2012, etc. may be referred to as input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above-mentioned input.

[0175] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle distance information, etc.) transmitted from external devices and displays it on the information service unit 2012 provided in the vehicle. The information service unit 2012 may also be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH received by the communication module 2013 (or data / information decoded from the PDSCH)).

[0176] Furthermore, the communication module 2013 stores various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, left and right front wheels 2007, left and right rear wheels 2008, axle 2009, sensors 2021 to 2029, and the like provided in the vehicle 2001.

[0177] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching a table, database, or other data structure), and ascertaining, all of which are considered to be "judging" and "determining." "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, and accessing (e.g., accessing data in memory), all of which are considered to be "judging" and "determining." "Determining" and "determining" may also include resolving, selecting, choosing, establishing, comparing, and other actions, all of which are considered to be "judging" and "determining." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Also, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0178] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0179] The reference signal may also be abbreviated as RS, and may be called a pilot depending on the applicable standard.

[0180] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0181] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must in some way precede the second element.

[0182] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0183] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0184] A radio frame may be composed of one or more frames in the time domain. Each of the one or more frames in the time domain may be called a subframe. A subframe may further be composed of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that is independent of numerology.

[0185] Numerology may be a communication parameter applied to the transmission and / or reception of a signal or channel, such as subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame structure, specific filtering operations performed by the transceiver in the frequency domain, specific windowing operations performed by the transceiver in the time domain, etc.

[0186] A slot may consist of one or more symbols in the time domain (such as Orthogonal Frequency Division Multiplexing (OFDM) symbols, Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols, etc.) A slot may be a time unit based on numerology.

[0187] A slot may include multiple minislots. Each minislot may consist of one or multiple symbols in the time domain. A minislot may also be called a subslot. A minislot may consist of fewer symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a minislot may be called PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a minislot may be called PDSCH (or PUSCH) mapping type B.

[0188] The radio frame, subframe, slot, minislot, and symbol all represent time units for transmitting signals, and may be referred to by other names corresponding to the radio frame, subframe, slot, minislot, and symbol.

[0189] For example, one subframe may be referred to as a transmission time interval (TTI), multiple consecutive subframes may be referred to as a TTI, or one slot or one minislot may be referred to as a TTI. That is, at least one of the subframe and the TTI may be a subframe (1 ms) in existing LTE, a period shorter than 1 ms (e.g., 1 to 13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be referred to as a slot, minislot, etc., instead of a subframe.

[0190] Here, TTI refers to, for example, the smallest time unit for scheduling in wireless communication. For example, in an LTE system, a base station schedules each terminal by allocating radio resources (such as frequency bandwidth and transmission power that can be used by each terminal) in TTI units. However, the definition of TTI is not limited to this.

[0191] The TTI may be a transmission time unit for a channel-encoded data packet (transport block), a code block, a code word, etc., or may be a processing unit for scheduling, link adaptation, etc. When a TTI is given, the time interval (e.g., the number of symbols) to which a transport block, a code block, a code word, etc. is actually mapped may be shorter than the TTI.

[0192] In addition, when one slot or one minislot is called a TTI, one or more TTIs (i.e., one or more slots or one or more minislots) may be the minimum time unit for scheduling. Furthermore, the number of slots (minislots) constituting the minimum time unit for scheduling may be controlled.

[0193] A TTI having a time length of 1 ms may be referred to as a regular TTI (TTI in LTE Rel. 8 to 12), normal TTI, long TTI, regular subframe, normal subframe, long subframe, slot, etc. A TTI shorter than a regular TTI may be referred to as a shortened TTI, short TTI, partial or fractional TTI, shortened subframe, short subframe, minislot, subslot, slot, etc.

[0194] In addition, a long TTI (e.g., a normal TTI, a subframe, etc.) may be interpreted as a TTI having a time length of more than 1 ms, and a short TTI (e.g., a shortened TTI, etc.) may be interpreted as a TTI having a TTI length shorter than the TTI length of a long TTI and equal to or greater than 1 ms.

[0195] A resource block (RB) is a resource allocation unit in the time domain and the frequency domain, and may include one or more consecutive subcarriers in the frequency domain. The number of subcarriers included in an RB may be the same regardless of numerology, for example, 12. The number of subcarriers included in an RB may be determined based on numerology.

[0196] The time domain of an RB may include one or more symbols and may have a length of one slot, one minislot, one subframe, or one TTI. One TTI, one subframe, etc. may each be composed of one or more resource blocks.

[0197] Note that one or more RBs may also be called a physical resource block (PRB), a sub-carrier group (SCG), a resource element group (REG), a PRB pair, an RB pair, etc.

[0198] Furthermore, a resource block may be composed of one or more resource elements (REs). For example, one RE may be a radio resource region of one subcarrier and one symbol. A bandwidth part (BWP) (which may also be referred to as a partial bandwidth) may represent a subset of contiguous common resource blocks (RBs) for a certain numerology in a certain carrier. Here, the common RBs may be identified by their indexes relative to the common reference point of the carrier. PRBs may be defined in a certain BWP and numbered within the BWP.

[0199] The BWP may include a BWP for UL (UL BWP) and a BWP for DL ​​(DL BWP). One or more BWPs may be configured for a UE within one carrier.

[0200] At least one of the configured BWPs may be active, and the UE may not expect to transmit or receive a predetermined signal / channel outside the active BWP. Note that the terms "cell," "carrier," etc. in this disclosure may be read as "BWP."

[0201] The above-described structures of radio frames, subframes, slots, minislots, symbols, etc. are merely examples, and various configurations, such as the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, the number of symbols in a TTI, the symbol length, and the cyclic prefix (CP) length, can be changed.

[0202] The "maximum transmit power" in this disclosure may mean the maximum value of the transmit power, the nominal UE maximum transmit power, or the rated UE maximum transmit power.

[0203] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0204] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0205] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure.

[0206] (Additional Note) The above disclosure may be expressed as follows.

[0207] A first feature is a base station including a central device, the central device including: a transceiver unit that transmits, to another base station, a message related to lower layer controlled mobility that causes a terminal connected to a first cell controlled by the base station to transition to a second cell controlled by the other base station; and a control unit that includes, in the message, an information element that requests the mobility that maintains a connection between the terminal and the central device, the control unit generates a confirmation message for the other base station to confirm whether the other base station can support the mobility that maintains the connection between the terminal and the central device, and the transceiver unit transmits the confirmation message to the other base station before transmitting the message.

[0208] A second feature is the base station according to the first feature, wherein the control unit includes a first control unit that controls a control plane and a second control unit that controls a user plane, and the confirmation message includes an information element that confirms whether an interface can be established between the second control unit and the other base station.

[0209] A third feature is a base station according to the first or second feature, wherein the control unit includes a first control unit that controls a control plane and a second control unit that controls a user plane, and the confirmation message includes an information element that confirms whether a bearer can be established between the second control unit and a distributed device that constitutes the other base station.

[0210] A fourth feature is the base station according to any one of the first to third features, wherein the transceiver unit receives capability information indicating whether the other base station is capable of supporting the communication.

[0211] A fifth feature is the base station based on any one of the second to fourth features, wherein the transceiver unit receives capability information indicating whether the interface can be established from the other base station.

[0212] A sixth feature is the base station according to any one of the third to fifth features, wherein the transceiver unit receives capability information indicating whether the bearer can be established from the other base station.

[0213] 10 Wireless communication system 20 NG-RAN 30 CN 100 Base station 110 Wireless signal transmitting / receiving unit 120 Amplifier unit 130 Modulation / demodulation unit 140 Control signal / reference signal processing unit 150 Encoding / decoding unit 160 Data transmitting / receiving unit 170 Control unit 200 Terminal 210 Wireless signal transmitting / receiving unit 220 Control unit 300 AMF 400 NWDAF 1001 Processor 1002 Memory 1003 Storage 1004 Communication device 1005 Input device 1006 Output device 1007 Bus 2001 Vehicle 2002 Drive unit 2003 Steering unit 2004 Accelerator pedal 2005 Brake pedal 2006 Shift lever 2007 Left and right front wheels 2008 Left and right rear wheels 2009 Axle 2010 Electronic control unit 2012 Information service unit 2013 Communication module 2021 Current sensor 2022 RPM sensor 2023 Air pressure sensor 2024 Vehicle speed sensor 2025 Acceleration sensor 2026 Brake pedal sensor 2027 Shift lever sensor 2028 Object detection sensor 2029 Accelerator pedal sensor 2030 Driving assistance system unit 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port (IO port)

Claims

1. A base station having a central device, wherein the central device comprises: a transceiver unit that transmits to another base station a message related to lower layer controlled mobility that transitions a terminal connected to a first cell controlled by the base station to a second cell controlled by the other base station; and a control unit that includes in the message an information element that requests the mobility that maintains the connection between the terminal and the central device, wherein the control unit generates a confirmation message to the other base station to confirm whether the other base station can support the mobility that maintains the connection between the terminal and the central device, and the transceiver unit transmits the confirmation message to the other base station before transmitting the message.

2. The base station according to claim 1, wherein the control unit comprises: a first control unit that controls a control plane; and a second control unit that controls a user plane; and the confirmation message includes an information element that confirms whether an interface can be established between the second control unit and the other base station.

3. The base station according to claim 1, wherein the control unit comprises: a first control unit that controls a control plane; and a second control unit that controls a user plane; and the confirmation message includes an information element that confirms whether a bearer can be established between the second control unit and a distributed device that constitutes the other base station.

4. The base station according to claim 1, wherein the transmitting / receiving unit receives capability information indicating whether the other base station is capable of supporting the communication.

5. The base station according to claim 2, wherein the transmitting / receiving unit receives capability information indicating whether the interface can be established from the other base station.

6. The base station according to claim 3, wherein the transmitting / receiving unit receives capability information indicating whether the bearer can be established from the other base station.

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