Terminal, wireless communication system, and wireless communication method

Abstract

This terminal executes cell switching, if mobility control by a lower layer fails, and transmits a connection reconfiguration request if the cell switching is not to a candidate cell that is in accordance with the mobility control. The terminal also receives a message including an update instruction for key information used for ensuring security with a network. If receiving the update instruction in the cell switching, the terminal updates the key information.

Description

Terminal, wireless communication system, and wireless communication method

[0001] The present disclosure relates to a terminal, a wireless communication system, and a wireless communication method that support LTM (L1 / L2 mobility).

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

[0003] For example, 3GPP Release 18 has expanded functionality related to Layer 1 / Layer 2 mobility (L1 / L2 mobility) (see Non-Patent Document 1). L1 / L2 mobility, also known as Lower Layer Triggered Mobility (LTM), is a technology related to the mobility of a terminal (User Equipment, UE) in Layer 1 or Layer 2, and includes the transition of a UE to another cell (handover (HO)). HO using LTM is realized by lower layers such as the Medium Access Control layer (MAC).

[0004] In addition, the document also specifies LTM fast failure recovery (which may also be referred to as LTM fast recovery), which is a mechanism in which, in the event of an LTM failure, the UE selects a cell to transition to, and if the selected cell is an LTM candidate cell, the UE directly applies the settings of the candidate cell without sending an RRC Reestablishment Request to the radio base station (gNB).

[0005] However, LTM fast recovery has a problem of key stream reuse, which is used to ensure security (Non-Patent Document 2). Therefore, it has been agreed that for signaling radio bearers (SRBs), the continuous use of Packet Data Convergence Protocol (PDCP) entities, i.e., the use of continuous COUNT values ​​(Count continuation), is required (Non-Patent Documents 3 and 4).

[0006] 3GPP TS 38.331 V18.1.0, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; NR; Radio Resource Control (RRC) protocol specification (Release 18), 3GPP, March 2024 "Keystream reuse issue caused by fast recovery after LTM cell switch", R2-2313310, 3GPP TSG-RAN WG2 Meeting #124, 3GPP, November 2023 "Report of 3GPP TSG RAN WG2 meeting #125", R2-2403994, 3GPP TSG-RAN WG2 meeting #125bis, 3GPP, April 2024 "Miscellaneous corrections on further mobility enhancements in NR", R2-2403174, 3GPP TSG-RAN WG2 meeting #125bis, 3GPP, April 2024

[0007] Since the Count continuation intentionally generates a gap in the sequence number (SN) of the COUNT value in the PDCP entity, the network must wait until the timer for correcting the order of data units, specifically the reordering timer, expires. Unlike Data Radio Bearers (DRBs), SRBs do not generally assume data unit loss, so the timer expiration time is often set very long.

[0008] Therefore, since the operation according to LTM fast recovery is also suspended until the reordering timer expires, there is a risk that the effectiveness of LTM fast recovery may be significantly impaired.

[0009] The following disclosure has been made in light of the above circumstances, and aims to provide a terminal, a wireless communication system, and a wireless communication method that can quickly apply LTM fast recovery while resolving the problem of security key reuse (key stream reuse) in LTM fast recovery.

[0010] One aspect of the present disclosure includes a control unit (control unit 240) that executes cell switching when mobility control by a lower layer fails, a transmission unit (handover execution unit 230) that transmits a connection reconfiguration request when the cell switching to a candidate cell is not in accordance with the mobility control, and a reception unit that receives a message including an instruction to update key information used to ensure security with the network, wherein the control unit is a terminal (UE 200) that updates the key information when the update instruction is received during the cell switching.

[0011] FIG. 1 is a schematic diagram of the overall configuration of a wireless communication system 10. FIG. 2 shows an example of control using L1 / L2 mobility (LTM). FIG. 3 is a functional block diagram of a gNB 100. FIG. 4 is a functional block diagram of a UE 200. FIG. 5 is a diagram showing an example of a basic sequence of cell switching according to LTM. FIG. 6 is a diagram showing an example of the configuration of an ltm-CandidateId list. FIG. 7 is a diagram showing an example of the configuration of an ltm-CandidateId list. FIG. 8 is a diagram showing example 1 of association between LTM-masterKeyUpdate and ltm-CandidateId. FIG. 9 is a diagram showing example 1 of association between LTM-masterKeyUpdate and ltm-CandidateId. FIG. 10 is a diagram showing example 2 of association between LTM-masterKeyUpdate and ltm-CandidateId. FIG. 11 is a diagram showing example 2 of association between LTM-masterKeyUpdate and ltm-CandidateId. FIG. 12 is a diagram showing an example of UE operation specifications related to an LTM cell switch. Fig. 13 is a diagram showing an example of the configuration of an LTM-config including two types of attemptLTM-switch. Fig. 14 is a diagram showing an example of the hardware configuration of the gNB 100 and the UE 200. Fig. 15 is a diagram showing an example of the configuration of a vehicle 2001.

[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) Overall Schematic Configuration of Wireless Communication System Fig. 1 is a diagram showing the overall schematic configuration of a wireless communication system 10 according to this embodiment. The wireless communication system 10 is a wireless communication system conforming to 5G New Radio (NR) and includes a Next Generation-Radio Access Network 20 (hereinafter, NG-RAN 20) and a terminal 200 (User Equipment 200, hereinafter, UE 200).

[0014] The wireless communication system 10 may be a wireless communication system conforming to a method called Beyond 5G, 5G Evolution, or 6G, or may include a wireless communication system conforming to a method called Long Term Evolution (LTE) or 4G. The wireless communication system 10 may support functions related to the Industrial Internet of Things (IIoT) and Ultra-Reliable and Low Latency Communications (URLLC).

[0015] The NG-RAN 20 includes a radio base station 100 (hereinafter, gNB 100). Note that the specific configuration of the radio communication system 10, including the number of gNBs (or eNBs, etc.) and UEs, is not limited to the example shown in FIG. 1 .

[0016] The gNB 100 may also employ a fronthaul (FH) interface defined by the Open Radio Access Network Alliance (O-RAN). The gNB 100 may include an O-RAN Distributed Unit (O-DU) and an O-RAN Radio Unit (O-RU). The gNB 100 can function as a type of NG-RAN node.

[0017] The NG-RAN 20 actually includes multiple NG-RAN nodes, specifically, gNBs (or ng-eNBs), and is connected to a 5G core network (5GC, not shown). The NG-RAN 20 and the 5GC may be simply referred to as a "network." The 5GC may introduce the concept of CUPS (Control and User Plane Separation), which clearly separates the functions of the user plane and the control plane.

[0018] The gNB100 is a radio base station conforming to NR and performs radio communication with the UE200 conforming to NR. The gNB100 may be configured to include a CU (Central Unit) and a DU (Distributed Unit), and the DU may be separated from the CU and installed in a different geographical location. One or more DUs may be connected to the CU. The gNB100 (gNB-CU) may be connected to each other via an Xn interface, and the CU and DU may be connected to each other via an F1 interface (such as an F1-AP).

[0019] The gNB100 and UE200 are capable of supporting Massive MIMO, which generates more directional beams by controlling radio signals transmitted from multiple antenna elements; Carrier Aggregation (CA), which aggregates and uses multiple component carriers (CCs); and Dual Connectivity (DC), which enables simultaneous communication between the UE and multiple NG-RAN nodes.

[0020] The type of DC may be Multi-RAT Dual Connectivity (MR-DC) that uses multiple radio access technologies, or NR-NR Dual Connectivity (NR-DC) that uses only NR. For example, one gNB may constitute a master node (MN), and one or more other gNBs may constitute secondary nodes (SNs).

[0021] In the wireless communication system 10, not only mobility control of the UE 200 at layer 3 (which may be referred to as L3 Mobility), but also mobility control at layer 1 and / or layer 2 (which may be referred to as L1 / L2 Mobility or LTM) may be applied. L3 Mobility may be interpreted as mobility control at the Radio Resource Control layer (RRC). On the other hand, L1 / L2 Mobility may be interpreted as mobility control at the physical layer (PHY), medium access control layer (MAC), radio link control layer (RLC), and packet data convergence protocol layer (PDCP) (mobility control by a lower layer).

[0022] In addition, in UE-based LTM, like conditional handover (CHO), the UE receives a specific execution condition from the radio base station (gNB), monitors the status according to the execution condition, and if the execution condition is satisfied, it may execute LTM.

[0023] It should be noted that LTM may include LTM fast failure recovery (LTM fast recovery). LTM fast recovery is a mechanism in which, in the event of an LTM failure, UE 200 performs cell selection, and if the selected cell is an LTM candidate cell, the UE 200 directly applies the configuration of the candidate cell (LTM cell switch) without transmitting an RRC Reestablishment Request to gNB 100. It should be noted that LTM fast recovery may be applied only to Intra-CU LTM, but does not exclude application to Inter-CU LTM.

[0024] In a broad sense, the mobility of UE200 may mean the ease of movement and maneuverability of UE200, but in this embodiment, it may also mean minimizing call drops, radio link (including beam) failures, unnecessary handovers, ping-pong states, etc.

[0025] Figure 2 shows an example of control by L1 / L2 mobility (LTM). As shown in Figure 2, MAC included in the lower layer (Layer 1 / Layer 2), rather than RRC included in Layer 3, can perform measurement reporting, handover (HO) decision from a source cell to a target cell (which may include candidates), and timer management for determining whether HO is successful.

[0026] The MAC may report information related to the measurement report, the HO decision, and the timer to a higher layer (RRC). The RRC may manage the state of radio resources associated with the cell transition of the UE 200 based on the report.

[0027] In this embodiment, the channels include a control channel and a data channel, such as a physical downlink control channel (PDCCH), a physical uplink control channel (PUCCH), a physical random access channel (PRACH), and a physical broadcast channel (PBCH).

[0028] The data channels include a physical downlink shared channel (PDSCH) and a physical uplink shared channel (PUSCH).

[0029] The reference signal includes a Demodulation Reference Signal (DMRS), a Sounding Reference Signal (SRS), a Phase Tracking Reference Signal (PTRS), and a Channel State Information-Reference Signal (CSI-RS), and the signal includes a channel and a reference signal. Furthermore, the data may refer to data transmitted via a data channel.

[0030] (2) Functional Block Configuration of Wireless Communication System Next, the functional block configuration of the wireless communication system 10 will be described. Specifically, the functional block configurations of the gNB 100 and the UE 200 will be described. Fig. 3 is a functional block configuration diagram of the gNB 100. Fig. 4 is a functional block configuration diagram of the UE 200.

[0031] (2.1) gNB100 As shown in FIG. 3, the gNB100 includes a radio communication unit 110, a handover processing unit 120, a measurement setting unit 130, and a control unit 140.

[0032] The wireless communication unit 110 transmits a downlink signal (DL signal) conforming to NR. The wireless communication unit 110 also receives an uplink signal (UL signal) conforming to NR. In this embodiment, the wireless communication unit 110 may transmit to the UE 200 a message related to ensuring security between the UE 200 and the network (specifically, the gNB 100) under the control of the control unit 140.

[0033] Specifically, the radio communication unit 110 may transmit a message regarding key information used to ensure security with the network. Here, the key information may be interpreted as information indicating the configuration of a key such as a private key used for encryption, signing, etc. to ensure security (which may mean confidentiality or integrity) between the UE 200 and the gNB 100 (which may be read as a cell).

[0034] More specifically, the key information may refer to a master key or a secondary key applied to a signaling radio bearer (SRB) and a data radio bearer (DRB). The SRB may include SRB0 to SRB3. SRB0 to SRB3 may be defined as follows:

[0035] SRB0: A radio bearer for RRC messages that uses the CCCH (Common Control Channel) logical channel.

[0036] SRB1: Radio bearer for RRC messages (which may include piggybacked NAS messages) and NAS messages before the establishment of SRB2, which uses the Dedicated Control Channel (DCCH) logical channel.

[0037] SRB2: Radio bearer for NAS messages using all DCCH logical channels. SRB2 has a lower priority than SRB1 and is always configured by the network after security is activated.

[0038] SRB3: A radio bearer for specific RRC messages when the UE 200 is in the MR-DC state, and uses the DCCH logical channel.

[0039] The DRB is a radio bearer mainly used for transmitting and receiving user data. The SRB and the DRB may be established between the UE 200 and the gNB 100.

[0040] The radio communication unit 110 may transmit a message including the above-described instruction to update the key information to the UE 200. In this embodiment, the radio communication unit 110 may constitute a transmission unit that transmits a message including the instruction to update the key information.

[0041] The key information update instruction may be, for example, an indication to update a master key (masterKeyUpdate). However, it is not necessarily limited to a master key. The update instruction may also be transmitted in LTM fast recovery. In other words, the update instruction may be applied only to LTM fast recovery.

[0042] The layer in which the message is transmitted may not be particularly limited, but typically, an RRC message may be used. The update instruction may also be included in an existing information element (IE) defined in the 3GPP specifications (e.g., LTM-config).

[0043] The handover processing unit 120 executes handover of the UE 200. Specifically, the handover processing unit 120 executes handover of the UE 200 from a serving cell to another nearby cell.

[0044] In particular, in this embodiment, the handover processing unit 120 can handle mobility control by a lower layer of the UE 200, specifically, handover (cell transition) according to LTM. Furthermore, the handover processing unit 120 can handle candidate cell selection and switching (LTM cell switch) according to LTM fast recovery of the UE 200.

[0045] The serving cell may be simply interpreted as a cell to which the UE 200 is connected, but more precisely, in the case of an RRC_CONNECTED UE in which carrier aggregation (CA) is not configured, there is only one serving cell that constitutes the primary cell. In the case of an RRC_CONNECTED UE configured using CA, the serving cell may be interpreted as indicating a set of one or more cells including the primary cell and all secondary cells.

[0046] The handover may also include a conditional handover (CHO) and / or a dual active protocol stack (DAPS) handover. CHO can execute a handover initiated by the UE 200 when a specific execution condition is met. If CHO is not applicable, a normal handover may be executed (which may be called CHO recovery). In CHO recovery, the UE 200 executes cell selection after a CHO failure. If a CHO candidate cell is selected, the UE 200 can directly apply conditional RRCReconfiguration of the selected cell to reconnect without transmitting an RRC Reestablishment Request to the candidate target cell.

[0047] The execution condition may consist of one or two trigger conditions (CHO event A3 / A5 specified in 3GPP TS38.331). A single reference signal (RS) type may be triggered, and up to two different trigger quantities (e.g., Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ), RSRP and Signal-to-Interference plus Noise power Ratio (SINR)) may be simultaneously set for the evaluation of the CHO execution condition for a single candidate cell.

[0048] In addition, the transition (handover) between candidate secondary nodes (which may also be read as target secondary nodes, target cells, or candidate cells, etc.) of a UE according to LTM may be called Inter-SN LTM.

[0049] The measurement configuration unit 130 performs configuration (measurement configuration) of quality measurements of the serving cell and neighboring cells by the UE 200. Specifically, the measurement configuration unit 130 may perform measurement configuration in layer 3, or may perform measurement configuration in layer 1 and / or layer 2.

[0050] The measurement configuration unit 130 can notify the UE 200 of the contents of the measurement configuration. The UE 200 can measure the quality of the serving cell and / or neighboring cells based on the notified measurement configuration. The measurement configuration unit 130 can receive a measurement report from the UE 200 indicating the measurement result of the cell quality.

[0051] The control unit 140 controls each functional block constituting the gNB 100. In particular, in this embodiment, the control unit 140 can perform mobility control with the UE 200. Specifically, the control unit 140 can perform not only mobility control according to L3 Mobility but also mobility control with the UE 200 according to L1 / L2 Mobility (LTM).

[0052] Furthermore, the control unit 140 can execute control related to the selection and switching of candidate cells in accordance with LTM fast recovery (LTM cell switch).

[0053] (2.2) UE 200 As shown in FIG. 4, the UE 200 includes a radio communication unit 210, a measurement reporting unit 220, a handover execution unit 230, and a control unit 240.

[0054] The wireless communication unit 210 transmits an uplink signal (UL signal) conforming to NR. The wireless communication unit 210 also receives an uplink signal (DL signal) conforming to NR. In this embodiment, the wireless communication unit 210 may receive a message including an instruction to update key information used to ensure security with the network (specifically, the gNB 100) under the control of the control unit 240. In this embodiment, the wireless communication unit 210 may constitute a receiving unit that receives a message including an instruction to update key information.

[0055] The key information update instruction may be, for example, an indication of "masterKeyUpdate" as described above. The wireless communication unit 210 may receive an update instruction associated with a list of identification information of candidate cells according to the LTM or a list for adding or changing the candidate cells.

[0056] The identification information of the candidate cell may be, for example, an ID (LTMcandidateId) of an LTM candidate. Furthermore, the list for adding or modifying candidate cells may be, for example, an LTM-candidateToAddModList (see 3GPP TS38.331). In this way, masterKeyUpdate may be associated with one or more LTMcandidateIds. Alternatively, masterKeyUpdate may be associated with at least one LTMcandidate in an LTM-candidateToAddModList that includes one or more LTMcandidateIds.

[0057] The measurement reporting unit 220 can measure the quality of the serving cell of the UE 200 and neighboring cells of the serving cell and report the measurement results (Measurement Report) to the network. The measurement reporting unit 220 can perform measurement reporting of the source cell and the target cell during handover.

[0058] The quality to be measured may be, for example, the quality included in the Measurement Report specified in 3GPP TS38.331 (e.g., Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ)).

[0059] The handover execution unit 230 executes handover of the UE 200. Specifically, the handover execution unit 230 may execute handover to a transfer destination cell (NG-RAN node) based on control by the gNB 100.

[0060] Furthermore, the handover execution unit 230 can execute processes related to normal handover (legacy handover), conditional handover (CHO), and DAPS handover.

[0061] In the case of CHO, the handover execution unit 230 may transition to the candidate cell when an execution condition is satisfied. As described above, the execution condition may be determined based on the quality of the reference signal (RS), specifically, the value of RSRP, RSRQ, or SINR.

[0062] In addition, the destination of the CHO may or may not be accompanied by an SCG. In other words, the destination cell of the CHO may be a single cell or may be composed of multiple cells (which may be read as a cell group) according to the DC.

[0063] Furthermore, the handover execution unit 230 may execute handover based on not only L3 mobility but also L1 / L2 mobility. Handover may be interpreted as transition, cell transition, cell selection, etc. Specifically, the handover execution unit 230 may execute handover based on L1 / L2 mobility based on at least one command of layer 1 and / or layer 2.

[0064] The type of the command is not particularly limited, and may be, for example, an L1 / L2 Mobility command. The L1 / L2 Mobility command may be replaced with another command in the RRC layer or a control element (CE) in the MAC layer. The handover executing unit 230 may receive configuration information related to L1 / L2 Mobility (LTM). The configuration information may mean configuration related to LTM (LTM-config). However, the information does not necessarily have to be LTM-config as long as it indicates configuration related to LTM (which may include execution conditions, etc.).

[0065] Furthermore, the handover execution unit 230 may transmit a reconfiguration request when the cell selected by the control unit 240 (which may be interpreted as a transition destination cell or a handover destination cell) is not a candidate cell (LTM candidate cell) according to L1 / L2 Mobility (LTM). In this embodiment, the handover execution unit 230 may constitute a transmission unit that transmits the reconfiguration request.

[0066] Specifically, the handover executing unit 230 may transmit an RRC Reestablishment Request to the network (gNB 100). Here, the destination of the RRC Reestablishment Request may be a CU or a DU. Note that the message is not necessarily limited to an RRC Reestablishment Request, and may be another message (for example, an RRC Resume Request) as long as it requests reconnection in the RRC layer.

[0067] The control unit 240 controls each functional block constituting the UE 200. Specifically, the control unit 240 can execute control relating to the registration of the UE 200 to the network (standby in a specific cell), measurement reporting, and handover of the UE 200.

[0068] The control unit 240 can also perform L1 / L2 mobility, i.e., mobility control of at least one of layer 1 and layer 2. Mobility control using L1 / L2 mobility may include quality measurement of service areas and neighboring cells in layer 1 or layer 2, setting of destination candidate cells, cell reselection (transition), handover, etc.

[0069] Furthermore, when L1 / L2 Mobility (LTM) fails (LTM failure), the control unit 240 can execute a cell switch of the transfer destination (LTM cell switch). Such an operation may be interpreted as the above-mentioned LTM fast recovery. Note that an LTM failure may include a failure in a measurement or transfer (handover) procedure accompanying a cell transfer by LTM.

[0070] When receiving a key update instruction in a cell switch accompanying an LTM fast recovery (LTM cell switch), the control unit 240 may update the key used to ensure security with the network. However, this is not necessarily limited to an LTM cell switch accompanying an LTM fast recovery.

[0071] For example, when the control unit 240 receives a masterKeyUpdate instruction, it may update the master key used for the SRB. Updating the master key may involve replacing the entire master key or changing some of the parameters of the master key.

[0072] The update instruction is not necessarily limited to the master key, but may also be directed to a secondary key. Also, the update instruction may be directed to not only the SRB but also the key used for the DRB. The SRB may be directed to all or some of the SRBs (SRB0 to SRB3).

[0073] On the other hand, if the control unit 240 has not received the update instruction as described above in the LTM cell switch, the control unit 240 may continue to use the PDCP entity. Specifically, the control unit 240 may use a continuous COUNT value in the PDCP entity (which may be called Count continuation). For example, if the COUNT value included in an RRC Reconfiguration Complete transmitted to the network at an arbitrary timing is "N," the control unit 240 may set a continuous count value (for example, "N+1") without reusing "N" at any timing after the arbitrary timing, and transmit the RRC Reconfiguration Complete again, even if the RRC Reconfiguration Complete does not arrive at the network.

[0074] Note that the control unit 240 may continue to use the PDCP entity for the SRB, but this does not preclude the control unit 240 from continuing to use the PDCP entity for the DRB.

[0075] (3) Operation of Wireless Communication System Next, we will explain the operation of the wireless communication system 10. Specifically, we will explain the operation that can quickly apply LTM fast recovery while solving the problem of security key reuse (key stream reuse) in LTM fast recovery.

[0076] (3.1) Assumptions and Issues Figure 5 shows an example of a basic sequence for cell switching according to LTM. As shown in Figure 5, the UE transmits a measurement report including quality measurement results of neighboring cells to the gNB (step 1). The gNB prepares candidate cells (LTM candidates) based on the quality of the neighboring cells, and transmits an RRC Reconfiguration including configuration information (LTM-config) related to LTM to the UE (step 2).

[0077] The UE returns RRC Reconfiguration Complete, performs early synchronization with the candidate cell, and transmits an L1 measurement report (steps 3 to 5).

[0078] The gNB decides to perform LTM (LTM cell switch) based on the quality of neighboring cells included in the measurement report, and sends a cell switch command to the UE (step 6).

[0079] The UE applies the configuration of the candidate target cell and completes the LTM (steps 7 and 8). Note that in the LTM, a random access channel (RACH) may be performed, or in certain cases, the RACH may be omitted.

[0080] Furthermore, in such a series of LTM sequences, if some kind of failure occurs, such as a message not being delivered, the UE selects a cell to transition to, and if the selected cell is an LTM candidate cell, an LTM fast recovery may be performed to directly apply the settings of the candidate cell without sending an RRC Reestablishment Request to the gNB.

[0081] That is, according to the current 3GPP specifications, if a radio link failure (RLF) or a re-configuration with sync failure occurs, attemptLTM-switch is configured, and the selected cell is an LTM candidate cell, LTM fast recovery may be performed.

[0082] In this case, the count continuation is applied to the state variable of the SRB1 of the PDCP. As described above, this count continuation can solve the problem of security key reuse (key stream reuse).

[0083] On the other hand, since Count continuation intentionally generates a gap in the sequence number (SN) of the COUNT value in the PDCP entity, the network must wait until the reordering timer expires.

[0084] Because the SRB reordering timer is set very long (perhaps by default it is infinite), the current procedure of having to wait until the reordering timer expires before each LTM fast recovery significantly reduces the effectiveness of LTM fast recovery.

[0085] An example of operation that can solve this problem will be described below.

[0086] (3.2) Operation Example The network may configure the UE with an indication (LTM-masterKeyUpdate) indicating that masterKeyUpdate is to be performed during LTM fast recovery. Specifically, the indication may be configured in RRC. That is, the network may transmit an RRC message including the indication to the UE.

[0087] This indication may be included in the LTM-config (see 3GPP TS38.331) (see step 2 in Fig. 2). Also, this indication may be set for each LTM candidate cell (ltm-candidate) or for each LTM-config.

[0088] The indication may be a list associated with the ID (LTMcandidateId) of the candidate cell, or may be associated with an LTM-candidate in the LTM-candidateToAddModList.

[0089] 6 and 7 show configuration examples of the ltm-CandidateId list. As shown in Fig. 6, LTM-config may include LTM-masterKeyUpdateList-r18 (which may be a tentative name) that indicates the list of LTM-masterKeyUpdates in sequence. Also, as shown in Fig. 7, ltm-CandidateId may be included in LTM-masterKeyUpdateList and associated with ltm-CandidateId in LTM-candidateToAddModList.

[0090] Figures 8 and 9 show example 1 of the association between LTM-masterKeyUpdate and ltm-CandidateId. As shown in Figure 8, LTM-config may include LTM-masterKeyUpdateList-r18 (this may be a tentative name), which indicates a list of LTM-masterKeyUpdate as a bit string. Also, as shown in Figure 9, LTM-masterKeyUpdateList, which indicates the presence or absence of an LTM-masterKeyUpdate, may be associated with ltm-CandidateId in LTM-candidateToAddModList.

[0091] 10 and 11 show example 2 of the association between LTM-masterKeyUpdate and ltm-CandidateId. As shown in Fig. 10, LTM-config may include LTM-masterKeyUpdateList-r18 (which may be a tentative name) indicating a list of LTM-masterKeyUpdate as a bit string, and LTM-CandidateIdList-r18 (which may be a tentative name) indicating a list of ltm-CandidateId as a bit string. Furthermore, as shown in Fig. 11, LTM-masterKeyUpdateList indicating the presence or absence of LTM-masterKeyUpdate, LTM-CandidateIdList indicating the presence or absence of ltm-CandidateId, and ltm-CandidateId in LTM-candidateToAddModList may be associated with each other.

[0092] Furthermore, if LTM-masterKeyUpdate is configured when performing an LTM cell switch by LTM fast recovery, the UE may perform masterKeyUpdate during LTM fast recovery. Specifically, when applying LTM fast recovery, the UE may update the master key used to ensure the security of the SRB.

[0093] On the other hand, if LTM-masterKeyUpdate is not configured when the UE performs an LTM cell switch by LTM fast recovery, the UE may perform one of the following operations without performing masterKeyUpdate during LTM fast recovery.

[0094] ・Perform PDCP Count continuation.

[0095] - PDCP Count continuation is performed and any SN gaps that occur are resolved.

[0096] As a method for resolving the SN gap, for example, the UE may transmit an RRC Reconfiguration Complete to the network (gNB) including an instruction to expire, stop, or reset the reordering timer on the gNB side, or an instruction to clear buffered PDCP data. Alternatively, the UE may add a PDCP header including an instruction to expire, stop, or reset the reordering timer, or may transmit a PDCP control PDU. In other words, the SN gap may be resolved by a method other than the RRC Reconfiguration Complete.

[0097] Fig. 12 shows an example of a specification of UE operation regarding an LTM cell switch. Specifically, Fig. 12 shows an example of a description of LTM cell switch execution specified in 3GPP TS38.331 Chapter 5.3.5.18.6.

[0098] As shown in Figure 12, when LTM-masterKeyUpdate is configured, the UE may revert to the configuration used in the source primary cell (PCell), including the state variables (see underlined part), i.e., the master key used to ensure the security of the SRB is updated, so the configuration used in the source primary cell (PCell), including the state variables, may be applied.

[0099] Furthermore, the network may configure the UE with a distinction between an indication of LTM fast recovery with count continuation and an indication of LTM fast recovery without count continuation. For example, "attemptLTM-switch-WithCountCont" (may be a tentative name) and "attemptLTM-switchWithoutCountCont" (may be a tentative name) may be defined.

[0100] Similarly, the network may configure the UE with a distinguishable indication of LTM fast recovery with masterKeyUpdate and an indication of LTM fast recovery without masterKeyUpdate. For example, "attemptLTM-switch-WithMasterKeyUpdate" (tentative names may be used) and "attemptLTM-switch-WithoutMasterKeyUpdate" may be specified.

[0101] Fig. 13 shows an example of the configuration of an LTM-config that includes two types of attemptLTM-switch. As shown in Fig. 13, the LTM-config may include an indication of LTM fast recovery with masterKeyUpdate (attemptLTM-switch-WithMasterKeyUpdate) and an indication of LTM fast recovery without masterKeyUpdate (attemptLTM-switch-WithoutMasterKeyUpdate).

[0102] Note that, while Figure 13 shows an example configuration in which attemptLTM-switch-WithMasterKeyUpdate and attemptLTM-switch-WithoutMasterKeyUpdate are set separately, in LTM-config, attemptLTM-switch-WithCountCont and attemptLTM-switchWithoutCountCont may also be set separately.

[0103] According to the above-described operation example, when the UE receives a masterKeyUpdate indication from the network, the UE may update the master key used for the SRB. The UE can also support PDCP Count continuation. Therefore, when the UE receives a masterKeyUpdate indication, the master key used for the SRB can be updated without waiting for the reordering timer to expire due to an SN gap, enabling LTM fast recovery to be applied quickly. Furthermore, updating the master key can also solve the problem of key stream reuse.

[0104] Furthermore, if the UE does not receive this indication, it can apply PDCP Count continuation, thereby continuing to solve the problem of key stream reuse.

[0105] In this embodiment, the UE can receive a list of identification information (LTMcandidateId) of candidate cells according to the LTM, or an indication of masterKeyUpdate associated with a list for adding or modifying the candidate cells (LTM-candidateToAddModList). This allows for flexible masterKeyUpdate according to cell classification, etc.

[0106] (4) Other Embodiments Although the embodiments have been described above, it will be obvious to those skilled in the art that the present invention is not limited to the description of the embodiments, and that various modifications and improvements are possible.

[0107] For example, although the above-described embodiment is premised on LTM fast recovery, LTM fast recovery does not necessarily have to be premised. In other words, the masterKeyUpdate indication may be applied not only to LTM fast recovery but also to LTM cell switch.

[0108] For example, in the above description, configure, activate, update, indicate, enable, specify, and select may be interchangeable. Similarly, link, associate, correspond, and map may be interchangeable, and allocate, assign, monitor, and map may be interchangeable.

[0109] Furthermore, specific, dedicated, UE-specific, and UE-dedicated may be interchangeable. Similarly, common, shared, group-common, UE-common, and UE-shared may be interchangeable.

[0110] The block diagrams (FIGS. 3 and 4) used to explain the above-described 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 the single device or multiple devices with software.

[0111] 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 each is implemented.

[0112] Furthermore, the above-described gNB 100 and UE 200 (the devices) may function as a computer that performs processing of the wireless communication method of the present disclosure. Figure 14 is a diagram showing an example of the hardware configuration of the devices. As shown in Figure 14, the devices may be configured as a computer 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.

[0113] In the following description, the term "apparatus" can be interpreted as a circuit, a device, a unit, etc. The hardware configuration of the apparatus 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.

[0114] Each functional block of the device (see FIGS. 3 and 4) is realized by any hardware element of the computer device or a combination of the hardware elements.

[0115] In addition, each function of the device is realized by loading specified software (programs) onto hardware such as processor 1001 and memory 1002, causing processor 1001 to perform calculations, control communication via communication device 1004, and control at least one of reading and writing data in memory 1002 and storage 1003.

[0116] 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 unit, an arithmetic unit, and registers.

[0117] 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. Furthermore, the various processes described above may be executed by a single processor 1001, or 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.

[0118] The memory 1002 is a computer-readable recording medium and may be configured by at least one of, for example, 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 may store a program (program code), a software module, etc., capable of executing a method according to an embodiment of the present disclosure.

[0119] 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 recording medium may be, for example, a database, a server, or other suitable medium including at least one of memory 1002 and storage 1003.

[0120] 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 called, for example, a network device, a network controller, a network card, or a communication module.

[0121] 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).

[0122] 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).

[0123] Furthermore, each device such as the processor 1001 and the memory 1002 is connected to 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.

[0124] Furthermore, the device 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, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0125] Furthermore, 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., 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.

[0126] Each aspect / embodiment described in the present disclosure may be applied 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), 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 other suitable system, and a next-generation system extended based on these. Furthermore, a combination of multiple systems (e.g., a combination of at least one of LTE and LTE-A with 5G) may also be applied.

[0127] 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.

[0128] In the present disclosure, a specific operation described as being performed by a base station may also 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 (e.g., MME or 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 (e.g., MME and S-GW) may also be used.

[0129] 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 and output via multiple network nodes.

[0130] The input and output information may be stored in a specific location (for example, a memory) or may be managed using a management table. The input and output information may be overwritten, updated, or added. The output information may be deleted. The input information may be transmitted to another device.

[0131] 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).

[0132] 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).

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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)).

[0142] The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage area.

[0143] 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.

[0144] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," etc. may be used interchangeably.

[0145] 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.

[0146] 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 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 also include devices that do 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.

[0147] Furthermore, a base station in the present disclosure may be read as a mobile station (user terminal, the same applies hereinafter). For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a mobile station is replaced with communication between multiple mobile stations (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the mobile station may be configured to have the functions of a base station. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel (or sidelink).

[0148] Similarly, a mobile station in the present disclosure may be interpreted as a base station, in which case the base station may have the functions of a mobile station.

[0149] 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.

[0150] Numerology may be communication parameters that apply 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, and specific windowing operations performed by the transceiver in the time domain.

[0151] A slot may consist of one or more symbols in the time domain (such as an Orthogonal Frequency Division Multiplexing (OFDM) symbol, a Single Carrier Frequency Division Multiple Access (SC-FDMA) symbol, etc.) A slot may be a numerology-based time unit.

[0152] A slot may include multiple minislots. Each minislot may consist of one or more 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.

[0153] 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.

[0154] 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., 1-13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, minislot, etc., instead of a subframe.

[0155] 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 user terminal to allocate radio resources (such as frequency bandwidth and transmission power that can be used by each user terminal) in TTI units. Note that the definition of TTI is not limited to this.

[0156] 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.

[0157] 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, and the number of slots (minislots) constituting the minimum time unit for scheduling may be controlled.

[0158] A TTI having a time length of 1 ms may be referred to as a regular TTI (TTI in LTE Rel. 8-12), 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.

[0159] 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.

[0160] 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.

[0161] 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, each of which may consist of one or more resource blocks.

[0162] 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.

[0163] 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.

[0164] A Bandwidth Part (BWP) (which may also be referred to as a fractional bandwidth) may represent a subset of contiguous common resource blocks (RBs) for a given numerology on a given carrier, where the common RBs may be identified by their index relative to a common reference point of the carrier. PRBs may be defined in a given BWP and numbered within that BWP.

[0165] 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.

[0166] At least one of the configured BWPs may be active, and the UE may not expect to transmit or receive a given signal / channel outside the active BWP. Note that the terms "cell," "carrier," etc. in this disclosure may be read as "BWP."

[0167] The above-described structures of the radio frame, subframe, slot, minislot, and symbol are merely examples. For example, 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, the cyclic prefix (CP) length, and other configurations may be changed in various ways.

[0168] 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.

[0169] The reference signal may also be abbreviated as Reference Signal (RS) and may be called a pilot depending on the applicable standard.

[0170] 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."

[0171] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0172] 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 therein or that the first element must precede the second element in some way.

[0173] 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.

[0174] 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.

[0175] 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 in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0176] 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."

[0177] 15 shows an example of the configuration of a vehicle 2001. As shown in Fig. 15, 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.

[0178] The drive unit 2002 is composed of, for example, an engine, a motor, or a hybrid of an engine and a motor. 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. The electronic control unit 2010 is composed of a microprocessor 2031, memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals from various sensors 2021 to 2027 provided in the vehicle are input to the electronic control unit 2010. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0179] The signals from the various sensors 2021 to 2028 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.

[0180] 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 1.

[0181] 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.

[0182] 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, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) 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.

[0183] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 1 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from a driving 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, a microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 2028, which are provided in the vehicle 2001.

[0184] 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.

[0185] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021 to 2028 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 2028, 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.

[0186] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle-to-vehicle information, etc.) transmitted from external devices and displays it on an 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 (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the 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, axles 2009, sensors 2021 to 2028, and the like provided in the vehicle 2001.

[0187] 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.

[0188] (Additional Note) The above disclosure may be expressed as follows.

[0189] The first feature is that the terminal includes a control unit that executes cell switching when mobility control by a lower layer fails, a transmission unit that transmits a connection reconfiguration request when the cell switching is not to a candidate cell in accordance with the mobility control, and a reception unit that receives a message including an instruction to update key information used to ensure security with the network, and the control unit is a terminal that updates the key information when the update instruction is received during the cell switching.

[0190] In a second feature based on the first feature, when the control unit has not received the update instruction in the cell switching, the control unit continues to use an entity of a packet data convergence protocol layer.

[0191] A third feature is the first or second feature, wherein the control unit continues to use the entity for a signaling radio bearer.

[0192] A fourth feature in any one of the first to third features is that the receiving unit receives the update instruction associated with a list of identification information of the candidate cells or a list for adding or changing the candidate cells.

[0193] 10 Wireless communication system 20 NG-RAN 100 gNB 110 Wireless communication unit 120 Handover processing unit 130 Measurement setting unit 140 Control unit 200 UE 210 Wireless communication unit 220 Measurement reporting unit 230 Handover execution unit 240 Control unit 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 section 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port

Claims

1. A terminal comprising: a control unit that executes cell switching when mobility control by a lower layer fails; a transmission unit that transmits a connection re-establishment request when the cell switching is not to a candidate cell in accordance with the mobility control; and a reception unit that receives a message including an instruction to update key information used to ensure security with a network, wherein the control unit updates the key information when the update instruction is received during the cell switching.

2. The terminal according to claim 1, wherein the control unit continues to use an entity of a packet data convergence protocol layer when the update instruction is not received during the cell switch.

3. The terminal according to claim 2, wherein the control unit continues to use the entity for a signaling radio bearer.

4. The terminal according to claim 1, wherein the receiving unit receives the update instruction associated with the list of identification information of the candidate cells or the list for adding or changing the candidate cells.

5. A wireless communication system including a terminal and a wireless base station, wherein the wireless base station comprises a transmitting unit that transmits to the terminal a message including an instruction to update key information used to ensure security with the network, and the terminal comprises: a control unit that executes cell switching when mobility control by a lower layer fails; a transmitting unit that transmits a request to reconfigure a connection when the cell switching is not to a candidate cell in accordance with the mobility control; and a receiving unit that receives the message including the update instruction, and the control unit updates the key information when the update instruction is received during the cell switching.

6. A wireless communication method in a terminal, comprising: a step of executing cell switching when mobility control by a lower layer fails; a step of sending a connection re-establishment request when the cell switching is not to a candidate cell in accordance with the mobility control; a step of receiving a message including an instruction to update key information used to ensure security with a network; and a step of updating the key information when the update instruction is received during the cell switching.

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