Terminal, wireless communication system, and wireless communication method

Abstract

The terminal performs cell handover in a case where low-layer-based mobility control fails, and transmits a connection reconfiguration request in a case where the cell handover is not to a candidate cell following the mobility control. In addition, the terminal receives a message including an update indication of key information for securing security with a network. The terminal updates the key information in a case where the update indication is received in the cell handover.

Description

Technical Field

[0001] This disclosure relates to terminals, wireless communication systems, and wireless communication methods that support LTM (L1 / L2 mobility). Background Technology

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

[0003] For example, 3GPP Release 18 expanded functionality related to Layer 1 / L2 mobility (Non-Patent Document 1). L1 / L2 mobility, also known as Lower Layer Triggered Mobility (LTM), is a technology related to the mobility of user equipment (UE) in Layer 1 or Layer 2, including UE migration to other cells (handover (HO)). LTM-based HO is implemented through lower layers such as the Media Access Control (MAC) layer.

[0004] In addition, LTM fast failure recovery (also known as LTM fast recovery) is also specified. The LTM fast failure recovery mechanism is as follows: When LTM fails, the UE performs cell selection for the migration destination. If the selected cell is an LTM candidate cell, it does not send an RRC Reestablishment Request to the gNB, but directly applies the settings of the candidate cell.

[0005] However, LTM fast recovery presents a problem with key stream reuse for ensuring security (Non-Patent Document 2). Therefore, regarding the Signaling Radio Bearer (SRB), it was agreed to continue using the Packet Data Convergence Protocol Layer (PDCP) entity, i.e., using continuous COUNT values ​​(Non-Patent Documents 3, 4).

[0006] Existing technical documents

[0007] Non-patent literature

[0008] Non-patent document 1: 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

[0009] Non-Patent Literature 2: "Keystream reuse issue caused by fast recovery after LTMcell switch", R2-2313310, 3GPP TSG-RAN WG2 Meeting #124, 3GPP, November 2023

[0010] Non-patent document 3: "Report of 3GPP TSG RAN WG2 meeting #125", R2-2403994, 3GPP TSG-RAN WG2 meeting #125bis, 3GPP, April 2024

[0011] Non-patent literature 4: "Miscellaneous corrections on further mobility enhancements in NR", R2-2403174, 3GPP TSG-RAN WG2 meeting #125bis, 3GPP, April 2024 Summary of the Invention

[0012] The aforementioned count continuation intentionally creates a gap (SN gap) in the sequence number (SN) of the COUNT value in the PDCP entity. Therefore, the network needs to remain on standby until the timer for data unit order correction, specifically the reorderingtimer, expires. In the case of SRB, unlike Data Radio Bearer (DRB), the loss of data units is generally not anticipated, so the time until the timer expires is usually set to be very long.

[0013] Therefore, since actions following LTM fast recovery are also retained until the reordering timer expires, the effectiveness of LTM fast recovery may be significantly impaired.

[0014] Therefore, the following disclosure is made in view of the following situation, with the aim of providing a terminal, wireless communication system, and wireless communication method that can eliminate the problem of key stream reuse in LTM fast recovery and can rapidly apply LTM fast recovery.

[0015] One aspect of this disclosure is a terminal (UE 200) comprising: a control unit (control unit 240) that performs cell handover in the event of a failure of low-level mobility control; a transmission unit (handover execution unit 230) that transmits a connection reset request when the cell handover is not to a candidate cell that follows the mobility control; and a receiving unit that receives a message containing an update instruction for key information to ensure security with the network, wherein the control unit updates the key information when it receives the update instruction during the cell handover. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the wireless communication system 10.

[0017] Figure 2 An example of control based on L1 / L2 mobility (LTM) is shown.

[0018] Figure 3 This is the function block structure diagram of gNB 100.

[0019] Figure 4 This is the function block structure diagram of UE 200.

[0020] Figure 5 This is a diagram illustrating a basic timing example of cell handover following LTM.

[0021] Figure 6 This is a diagram showing an example of the structure of a list of ltm-CandidateIds.

[0022] Figure 7 This is a diagram showing an example of the structure of a list of ltm-CandidateIds.

[0023] Figure 8This is a diagram illustrating Example 1 of the association between LTM-masterKeyUpdate and ltm-CandidateId.

[0024] Figure 9 This is a diagram illustrating Example 1 of the association between LTM-masterKeyUpdate and ltm-CandidateId.

[0025] Figure 10 This is a diagram illustrating Example 2 of the association between LTM-masterKeyUpdate and ltm-CandidateId.

[0026] Figure 11 This is a diagram illustrating Example 2 of the association between LTM-masterKeyUpdate and ltm-CandidateId.

[0027] Figure 12 This is a diagram illustrating a prescribed example of UE actions related to LTM cell switching.

[0028] Figure 13 This is a diagram illustrating an example structure of an LTM-config that includes two attemptLTM-switches.

[0029] Figure 14 This is a diagram illustrating an example of the hardware structure of gNB 100 and UE 200.

[0030] Figure 15 This is a diagram showing a structural example of vehicle 2001. Detailed Implementation

[0031] The embodiments are described below based on the accompanying drawings. Furthermore, the same or similar reference numerals are used to denote the same function or structure, and their descriptions are omitted where appropriate.

[0032] (1) Overall general structure of wireless communication system

[0033] Figure 1 This is a schematic diagram of the overall structure of the wireless communication system 10 involved in this embodiment. The wireless communication system 10 is a wireless communication system that follows 5G New Radio (NR) and includes a Next Generation Radio Access Network (NG-RAN 20) and a terminal 200 (User Equipment 200, UE 200).

[0034] Furthermore, the wireless communication system 10 can be a wireless communication system following protocols known as Beyond 5G, 5G Evolution, or 6G, or it can include wireless communication systems following protocols known as Long Term Evolution (LTE) or 4G. The wireless communication system 10 can support functions related to the Industrial Internet of Things (IIoT) and Ultra-Reliable and Low Latency Communications (URLLC).

[0035] NG-RAN 20 includes a radio base station 100 (hereinafter referred to as gNB 100). Furthermore, the specific structure of the wireless communication system 10, including the number of gNBs (or eNBs, etc.) and UEs, is not limited to... Figure 1 The example shown.

[0036] Additionally, the gNB 100 can also use the fronthaul (FH) interface defined by the O-RAN (Open Radio Access Network Alliance). The gNB 100 can include an O-DU (O-RAN Distributed Unit) and an O-RU (O-RAN Radio Unit). The gNB100 can function as an NG-RAN node.

[0037] NG-RAN 20 actually comprises multiple NG-RAN nodes, specifically multiple gNBs (or ng-eNBs), connected to a 5G-compliant core network (5GC, not shown). NG-RAN 20 and 5GC can also be simply referred to as a "network." Within 5GC, the concept of CUPS (Control and User Plane Separation), which explicitly separates the functions of the user plane and the control plane, can be introduced.

[0038] The gNB 100 is a NR-compliant radio base station that performs NR-compliant wireless communication with the UE 200. Furthermore, the gNB 100 can be configured to include a CU (Central Unit) and a DU (Distributed Unit), with the DU located separately from the CU in geographically distinct locations. The CU can connect to one or more DUs. Additionally, gNB 100s (gNB-CU) can connect to each other via the Xn interface, and CUs and DUs can connect via the F1 interface (F1-AP, etc.).

[0039] The gNB 100 and UE 200 can support Massive MIMO, which generates more directional beams by controlling radio signals transmitted from multiple antenna elements; Carrier aggregation (CA), which uses multiple component carriers (CC); and Dual connectivity (DC), which enables simultaneous communication between the UE and various nodes of multiple NG-RAN nodes.

[0040] The DC can be of the following types: Multi-RAT Dual Connectivity (MR-DC) which utilizes multiple wireless access technologies, or NR-NR Dual Connectivity (NR-DC) which utilizes only NR. For example, any gNB can form the master node (MN), and one or more other gNBs can form the slave nodes (SN).

[0041] In the wireless communication system 10, not only can the mobility control of UE 200 in Layer 3 (also known as L3Mobility) be applied, but also the mobility control in Layer 1 and / or Layer 2 (also known as L1 / L2Mobility or LTM) can be applied. L3Mobility can be interpreted as mobility control in the Radio Resource Control (RRC) layer. On the other hand, L1 / L2Mobility can be interpreted as mobility control in the Physical Layer (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP) layer (based on lower-layer mobility control).

[0042] In addition, in UE-based LTM, similar to Conditional Handover (CHO), the UE can monitor the state according to the execution condition after receiving a specific execution condition from the gNB, and execute LTM when the execution condition is met.

[0043] Furthermore, LTM can also include LTM fast failure recovery. LTM fast recovery works as follows: In the event of an LTM failure, the UE 200 performs cell selection. If the selected cell is an LTM candidate cell, it does not send an RRC Reestablishment Request to the gNB 100, but directly applies the settings of the candidate cell (LTM cell switch). Moreover, LTM fast recovery can be limited to Intra-CU LTM, but its application to Inter-CU LTM is not excluded.

[0044] In a broad sense, the mobility of UE 200 can refer to the ease of movement and maneuverability of UE 200. In this embodiment, it can also refer to the minimization of call drop, radio link (including beam) failure, unnecessary handover, ping-pong state, etc.

[0045] Figure 2 This illustrates a control example based on L1 / L2 mobility (LTM). For example... Figure 2 As shown, it is not the RRC contained in layer 3, but the MAC contained in the lower layers (layer 1 / layer 2) that can perform measurement reports, handover (HO) decisions from the source cell to the target cell (which may also include candidates), and timer management to determine whether the HO is successful.

[0046] The MAC can report information related to measurement reports, HO decisions, and timers to higher layers (RRC). The RRC can then use this report to manage the status of radio resources accompanying the cell migration of UE 200.

[0047] In addition, in this embodiment, the channel includes a control channel and a data channel. The control channel includes PDCCH (Physical Downlink Control Channel), PUCCH (Physical Uplink Control Channel), PRACH (Physical Random Access Channel), and PBCH (Physical Broadcast Channel), etc.

[0048] In addition, data channels include PDSCH (Physical Downlink Shared Channel) and PUSCH (Physical Uplink Shared Channel).

[0049] In addition, reference signals include demodulation reference signals (DMRS), sounding reference signals (SRS), phase tracking reference signals (PTRS), and channel state information reference signals (CSI-RS), etc. The signals encompass both the channel and the reference signals. Furthermore, data can refer to data transmitted via a data channel.

[0050] (2) Functional block structure of wireless communication system

[0051] Next, the functional block structure of the wireless communication system 10 will be described. Specifically, the functional block structures of gNB 100 and UE200 will be described. Figure 3 This is the function block structure diagram of gNB 100. Figure 4 This is the function block structure diagram of UE 200.

[0052] (2.1) gNB 100

[0053] like Figure 3 As shown, the gNB 100 includes a wireless communication unit 110, a switching processing unit 120, a measurement setting unit 130, and a control unit 140.

[0054] The wireless communication unit 110 transmits downlink signals (DL signals) conforming to NR. Additionally, the wireless communication unit 110 receives uplink signals (UL signals) conforming to NR. In this embodiment, the wireless communication unit 110 can, under the control of the control unit 140, transmit messages related to security assurance between the UE 200 and the network (specifically, gNB 100).

[0055] Specifically, the wireless communication unit 110 can send a message about key information used to ensure security with the network. Here, key information can be interpreted as information representing the structure of keys such as private keys used for encryption, signing, etc., to ensure security (confidentiality or integrity) between the UE 200 and gNB 100 (or alternatively, the cell).

[0056] More specifically, key information can also refer to the master key or sub-key applied to the signaling radio bearer (SRB) and data radio bearer (DRB). An SRB can contain SRB0 to 3. SRB0 to 3 can also be defined as follows.

[0057] • SRB0: This is the radio bearer used for RRC messages that utilize the CCCH (Common Control Channel) logical channel.

[0058] • SRB1: This is the radio bearer used for RRC messages (which may also include piggybacked NAS messages) and NAS messages established before the establishment of SRB2. It uses the DCCH (Dedicated Control Channel) logical channel.

[0059] • SRB2: This is the radio bearer used for NAS messages using all DCCH logical channels. SRB2 has a lower priority than SRB1 and is always constructed by the network after security is activated.

[0060] • SRB3: This is a radio bearer for specific RRC messages used by UE 200 in MR-DC state, using the DCCH logical channel.

[0061] DRB is a radio bearer primarily used for transmitting and receiving user data. SRB and DRB can be configured between UE 200 and gNB 100.

[0062] The wireless communication unit 110 can send a message containing the aforementioned key information to the UE 200. In this embodiment, the wireless communication unit 110 can be configured as a sending unit that sends a message containing the key information update instruction.

[0063] The key information update indication can be, for example, an indication of a master key update (masterKeyUpdate). However, it is not limited to the master key. Furthermore, this update indication can also be sent during LTM fast recovery. That is, the update indication can also be limited to LTM fastrecovery.

[0064] Furthermore, the layer from which the message is sent is not specifically limited; typically, an RRC message can be used. Additionally, the update instruction can also be included in existing information elements (IEs) specified in the 3GPP specification (e.g., LTM-config).

[0065] The handover processing unit 120 performs the handover of UE 200. Specifically, the handover processing unit 120 performs the handover of UE 200 from the serving cell to another neighboring cell.

[0066] In particular, in this embodiment, the handover processing unit 120 is capable of handling low-layer mobility control of the UE 200, specifically, it is capable of handling handover (cell migration) following LTM. In addition, the handover processing unit 120 is capable of handling the selection of candidate cells and handover (LTM cell switch) of the UE 200 following LTM fast recovery.

[0067] Furthermore, the serving cell can be simply interpreted as the cell in the UE 200 connection, but more strictly speaking, in the case of an RRC_CONNECTED UE without carrier aggregation (CA) configured, there is only one serving cell constituting the primary cell. In the case of an RRC_CONNECTED UE using CA, the serving cell can be interpreted as a set of one or more cells that includes the primary cell and all secondary cells.

[0068] Additionally, handover can include Conditional Handover (CHO) and / or DAPS (dual-active protocol stack) handover. CHO enables UE 200-led handover when specific execution conditions are met. In cases where CHO cannot be applied, a normal handover (also known as CHO recovery) can be performed. In CHO recovery, after CHO failure, UE 200 performs cell selection. However, if a CHO candidate cell is selected, it can directly apply the conditional RRC Reconfiguration of that cell for reconnection without sending an RRC Reestablishment Request to the candidate target cell.

[0069] The execution conditions can consist of one or two trigger conditions (CHO events A3 / A5 as specified in 3GPP TS38.331). A single reference signal (RS) type is triggered. To evaluate the CHO execution conditions of a single candidate cell, up to two different trigger values ​​can be set simultaneously (e.g., Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ), RSRP and Signal-to-Interference plus Noise power Ratio (SINR), etc.).

[0070] In addition, the migration (handover) between candidate secondary nodes (which can also be replaced by target secondary nodes, target cells, or candidate cells, etc.) of UEs that follow LTM can also be called Inter-SN LTM.

[0071] The measurement setting unit 130 performs the setting (measurement setting) of the quality measurement of the serving cell and neighboring cells performed by the UE 200. Specifically, the measurement setting unit 130 can perform the measurement configuration in layer 3, or the measurement configuration in layer 1 and / or layer 2.

[0072] The measurement setting unit 130 can notify the UE 200 of the measurement settings. The UE 200 can measure the quality of the serving cell and / or neighboring cells based on the notified measurement settings. The measurement setting unit 130 can receive a measurement report from the UE 200 representing the measurement results of the cell quality.

[0073] The control unit 140 controls the functional blocks constituting the gNB 100. In particular, in this embodiment, the control unit 140 is capable of performing mobility control with the UE 200. Specifically, the control unit 140 is capable of performing mobility control with the UE 200 not only according to L3 Mobility, but also according to L1 / L2 Mobility (LTM).

[0074] In addition, the control unit 140 is capable of performing control related to the selection of candidate cells following LTM fast recovery and handover (LTM cell switch).

[0075] (2.2) UE 200

[0076] like Figure 4 As shown, the UE 200 includes a wireless communication unit 210, a measurement reporting unit 220, a handover execution unit 230, and a control unit 240.

[0077] The wireless communication unit 210 transmits an uplink signal (UL signal) conforming to NR. Additionally, the wireless communication unit 210 receives an uplink signal (DL signal) conforming to NR. In this embodiment, the wireless communication unit 210 can, under the control of the control unit 240, receive a message containing an update instruction for key information used to ensure security with the network (specifically, gNB 100). In this embodiment, the wireless communication unit 210 can be configured as a receiving unit that receives messages containing update instructions for key information.

[0078] As described above, the key information update indication may be, for example, an indication indicating masterKeyUpdate. The wireless communication unit 210 may also receive an update indication associated with a list of identification information of candidate cells following LTM, or a list of additions or changes to the candidate cells.

[0079] The identification information of a candidate cell can be, for example, the ID (LTMcandidateId) of an LTM candidate. Additionally, the list used for adding or changing candidate cells can be, for example, an LTM-candidateToAddModList (refer to 3GPP TS38.331). Thus, masterKeyUpdate can also be associated with one or more LTMcandidateIds. Alternatively, masterKeyUpdate can be associated with at least one LTMcandidate in an LTM-candidateToAddModList containing one or more LTMcandidateIds.

[0080] The measurement reporting unit 220 is capable of measuring the quality of the serving cell of the UE 200 and its neighboring cells, and reporting the measurement results to the network. The measurement reporting unit 220 can perform measurement reports for the source cell and the target cell during handover.

[0081] The quality of the measured object can be, for example, the quality contained in the measurement report specified in 3GPP TS38.331 (e.g., Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ)).

[0082] The handover execution unit 230 performs the handover of UE 200. Specifically, the handover execution unit 230 can perform the handover to the destination cell (NG-RAN node) based on the control of gNB 100.

[0083] In addition, the switching execution unit 230 can perform processing related to normal switching (traditional switching), conditional switching (CHO), and DAPS switching.

[0084] In the case of CHO, the handover execution unit 230 can migrate to the candidate cell when the execution condition is met. As mentioned above, the execution condition can be determined based on the quality of the reference signal (RS), specifically based on the values ​​of RSRP, RSRQ, or SINR.

[0085] Furthermore, the destination of a CHO migration can be either without an SCG or with an SCG. In other words, the cell that serves as the destination for a CHO-based migration can be a single cell or a group of multiple cells following a DC (or a cell group).

[0086] Furthermore, the handover execution unit 230 can perform not only L3 mobility-based handovers but also L1 / L2 mobility-based handovers. Handover can be replaced by migration, cell migration, cell selection, etc. Specifically, the handover execution unit 230 can perform L1 / L2 mobility-based handovers based on at least one command from Layer 1 and / or Layer 2.

[0087] There is no particular limitation on the type of command; for example, it can be an L1 / L2 mobility command. This L1 / L2 mobility command can also be replaced by other commands in the RRC layer or control elements (CEs) in the MAC layer.

[0088] The switching execution unit 230 can also receive setting information related to L1 / L2 Mobility (LTM). This setting information may refer to LTM-related settings (LTM-config). However, as long as it represents LTM-related settings (which may also include execution conditions, etc.), it does not necessarily have to be LTM-config.

[0089] Furthermore, the handover execution unit 230 may send a reset request if the cell selected by the control unit 240 (which can also be interpreted as the cell of the migration destination or the cell of the handover destination) is not a candidate cell (LTM candidate cell) that follows L1 / L2 Mobility (LTM). In this embodiment, the handover execution unit 230 may be configured as a sending unit that sends reset requests.

[0090] Specifically, the handover execution unit 230 can send an RRC Reestablishment Request to the network (gNB 100). The destination of the RRC Reestablishment Request can be either the CU or the DU. Furthermore, any message requesting reconnection in the RRC layer is not necessarily limited to an RRC Reestablishment Request; other messages (e.g., an RRC Resume Request) are also possible.

[0091] The control unit 240 controls the functional blocks that constitute the UE 200. Specifically, the control unit 240 can perform controls related to the UE 200's registration with the network (waiting in a specific cell), measurement reporting, and the UE 200's handover.

[0092] In addition, the control unit 240 is capable of performing mobility control based on L1 / L2 Mobility, i.e., at least one of Layer 1 and Layer 2. Mobility control based on L1 / L2 Mobility may include quality measurement of the service area and neighboring cells in Layer 1 or Layer 2, setting of candidate cells for migration destination, cell reselection (migration), handover, etc.

[0093] Furthermore, in the event of an L1 / L2 Mobility (LTM) failure, the control unit 240 can perform an LTM cell switch at the destination. This action can also be interpreted as the LTM fast recovery described above. In addition, an LTM failure may include failures in the measurement or migration (handover) process that accompany LTM-based cell migration.

[0094] The control unit 240 can update the key information used to ensure security with the network when it receives an update instruction for key information during LTM cellwitch accompanied by LTM fast recovery. However, it is not necessarily limited to LTM cellwitch accompanied by LTM fast recovery.

[0095] For example, the control unit 240 can update the master key used for SRB upon receiving an instruction to masterKeyUpdate. Updating the master key can refer to replacing the entire master key or changing a portion of its parameters.

[0096] Furthermore, update instructions are not necessarily limited to the master key; they can also target subkeys. Additionally, not only SRBs can be targets, but also keys used for DRBs. An SRB can target all SRBs 0-3, or only a portion of them.

[0097] On the other hand, even if the control unit 240 does not receive the aforementioned update instruction in the LTM cell switch, it can still continue using the PDCP entity. Specifically, the control unit 240 can use consecutive COUNT values ​​(which can be called count continuation) in the PDCP entity. For example, if the COUNT value included in the RRC Reconfiguration Complete sent to the network at any given time is "N", even if the RRC Reconfiguration Complete is not delivered to the network, the control unit 240 can, at a time after that given time, set a consecutive count value (e.g., "N+1") instead of using "N" and resend the RRC Reconfiguration Complete.

[0098] Furthermore, the control unit 240 may continue to use the PDCP entity with SRB as the target. However, it is not excluded that the control unit 240 may continue to use the PDCP entity with DRB as the target.

[0099] (3) Operation of wireless communication system

[0100] Next, the operation of the wireless communication system 10 will be explained. Specifically, the operation of eliminating the problem of key stream reuse and rapidly applying LTM fast recovery in LTM fast recovery will be explained.

[0101] (3.1) Prerequisites and topics

[0102] Figure 5 This shows a basic timing example for cell handover following LTM. For example... Figure 5 As shown, the UE sends a measurement report containing the quality measurement results of neighboring cells to the gNB (step 1). Based on the quality of neighboring cells, the gNB prepares candidate cells (LTM candidate) and sends an RRC reconfiguration containing LTM-related configuration information (LTM-config) to the UE (step 2).

[0103] The UE sends back RRC Reconfiguration Complete, performs early synchronization with the candidate cell, and sends the L1 measurement report (steps 3-5).

[0104] Based on the quality of neighboring cells included in the measurement report, the gNB determines the execution of LTM (LTM cellswitch) and sends a cell handover command to the UE (step 6).

[0105] The UE sets the candidate cell for the handover destination and completes LTM (steps 7 and 8). In addition, the Random Access Procedure (RACH) can be performed in LTM, and in certain cases, the RACH can be omitted.

[0106] In addition, in such a series of LTM timings, in the event of certain faults such as message non-delivery, the UE performs cell selection for the migration destination. If the selected cell is an LTM candidate cell, it can also perform LTM fast recovery by directly applying the settings of the candidate cell without sending an RRC Reestablishment Request to the gNB.

[0107] In other words, according to the current 3GPP specifications, in the event of a radio link failure (RLF) or a re-configuration with sync failure, if attemptLTM-switch is set and the selected cell is an LTM candidate cell, LTM fast recovery can be performed.

[0108] Additionally, in this case, Count continuation is applied to the state variable of PDCP's SRB1. As mentioned above, this Count continuation eliminates the problem of key stream reuse.

[0109] On the other hand, the Count continuation intentionally creates a gap (SN gap) in the sequence number (SN) of the COUNT value in the PDCP entity, so the network needs to standby until the reordering timer expires.

[0110] Because the reordering timer of SRB is set to be very long (and may be infinitely long by default), the current process of having to wait for each LTM fast recovery until the reordering timer expires significantly impairs the effectiveness of LTM fast recovery.

[0111] The following are examples of actions that can eliminate such problems.

[0112] (3.2) Example of an action

[0113] The network can configure the UE to perform a masterKeyUpdate (LTM-masterKeyUpdate) during LTM fast recovery. Specifically, this indication can be set in the RRC. That is, the network can send an RRC message containing this indication to the UE.

[0114] This indication can be included in the LTM-config (refer to 3GPP TS38.331) (see...). Figure 2(Step 2). Additionally, this indication can be set for each LTM candidate cell (ltm-candidate) or each LTM-config.

[0115] The indication can be a list associated with the ID of the candidate cell (LTMcandidateId), or it can be associated with an LTM-candidate in LTM-candidateToAddModList.

[0116] Figure 6 as well as Figure 7 This shows an example of the structure of a list of ltm-CandidateIds. For example... Figure 6 As shown, the LTM-config can contain an LTM-masterKeyUpdateList-r18 (which can be a temporary name) that represents a list of LTM-masterKeyUpdates using sequences. Additionally, as... Figure 7 As shown, ltm-CandidateId can also be included in LTM-masterKeyUpdateList and associated with ltm-CandidateId in LTM-candidateToAddModList.

[0117] Figure 8 as well as Figure 9 Example 1 illustrates the association between LTM-masterKeyUpdate and ltm-CandidateId. For example... Figure 8 As shown, the LTM-config can contain an LTM-masterKeyUpdateList-r18 (which can be a temporary name) that represents a list of LTM-masterKeyUpdates as bit strings. Additionally, as... Figure 9 As shown, the LTM-masterKeyUpdateList, which indicates whether LTM-masterKeyUpdate exists, can also be associated with the ltm-CandidateId in the LTM-candidateToAddModList.

[0118] Figure 10 as well as Figure 11 Example 2 illustrates the association between LTM-masterKeyUpdate and ltm-CandidateId. For example... Figure 10As shown, the LTM-config can contain LTM-masterKeyUpdateList-r18 (which can be a temporary name) which represents a list of LTM-masterKeyUpdates using bit strings, and LTM-CandidateIdList-r18 (which can be a temporary name) which represents a list of ltm-CandidateIds using bit strings. Additionally, as... Figure 11 As shown, you can also associate the LTM-masterKeyUpdateList (indicating whether LTM-masterKeyUpdate exists), the LTM-CandidateIdList (indicating whether ltm-CandidateId exists), and the ltm-CandidateId in LTM-candidateToAddModList.

[0119] Additionally, if LTM-masterKeyUpdate is configured during LTM cell handover via LTM fast recovery, the UE can perform masterKeyUpdate during LTM fast recovery. Specifically, the UE can update the master key used for SRB security assurance when applying LTM fast recovery.

[0120] On the other hand, if LTM-masterKeyUpdate is not set when performing LTM cellwitch via LTM fast recovery, the UE can perform any subsequent action without executing masterKeyUpdate during LTM fast recovery.

[0121] • Perform PDCP Count continuation.

[0122] • Perform PDCP Count continuation and eliminate any resulting SN gaps.

[0123] As a method to eliminate the SN gap, for example, the UE can send an RRC Reconfiguration Complete message to the network (gNB) containing an indication that the reordering timer on the gNB side has expired, stopped, or reset, or that data to clear the PDCP buffer. Alternatively, it can provide a PDCP header containing an indication that the reordering timer has expired, stopped, or reset, or it can send a PDCP control PDU. That is to say, the SN gap can also be eliminated by methods other than RRC Reconfiguration Complete.

[0124] Figure 12 This section illustrates examples of UE actions related to LTM cell switching. Specifically, Figure 12 This shows a documented example of LTM cell switch execution as specified in Chapter 5.3.5.18.6 of 3GPP TS38.331.

[0125] like Figure 12 As shown, with LTM-masterKeyUpdate set, the UE can return to the settings used in the source master cell (PCell) including state variables (see underlined section). That is, the master key used for SRB security assurance is updated, and therefore the settings including state variables used in the internal source master cell (PCell) can be applied.

[0126] Additionally, the network can differentiate the indication of LTM fast recovery with and without count continuation for the UE. For example, it can specify attemptLTM-switch-WithCountCont (which can be a temporary name) and attemptLTM-switchWithoutCountCont (which can also be a temporary name).

[0127] Similarly, the network can also differentiate the indication of LTM fast recovery that accompanies masterKeyUpdate from the indication of LTM fast recovery that does not accompanies masterKeyUpdate to the UE. For example, attemptLTM-switch-WithMasterKeyUpdate (which can be a temporary name) and attemptLTM-switch-WithoutMasterKeyUpdate can be specified.

[0128] Figure 13 This example shows the structure of an LTM-config that includes two attemptLTM-switch methods. For example... Figure 13 As shown, the LTM-config can contain an indication for LTM fast recovery that accompanies masterKeyUpdate (attemptLTM-switch-WithMasterKeyUpdate) and an indication for LTM fast recovery that does not accompanies masterKeyUpdate (attemptLTM-switch-WithoutMasterKeyUpdate).

[0129] In addition, Figure 13 The example shown illustrates a structure for setting `attemptLTM-switch-WithMasterKeyUpdate` and `attemptLTM-switch-WithoutMasterKeyUpdate` differently. However, in the LTM-config, `attemptLTM-switch-WithCountCont` and `attemptLTM-switchWithoutCountCont` can also be set differently.

[0130] Based on the above action example, the UE can update the master key used for SRB upon receiving the masterKeyUpdate indication from the network. Furthermore, the UE also supports PDCP count continuation. Therefore, if the masterKeyUpdate indication is received, the master key used for SRB can be updated without waiting for the reordering timer associated with the SN gap to expire, thus enabling rapid application of LTM fast recovery. Additionally, updating the master key eliminates the problem of key stream reuse.

[0131] In addition, even if the UE does not receive this indication, it can apply the PDCP count continuation, thus continuing to eliminate the key stream reuse problem.

[0132] In this embodiment, the UE can receive a masterKeyUpdate indication associated with a list of LTM-compliant candidate cell identification information (LTMcandidateId) or a list of candidate cells for addition or modification (LTM-candidateToAddModList). Therefore, flexible masterKeyUpdate corresponding to cell types can be supported.

[0133] (4) Other implementation methods

[0134] The above describes the embodiments, but the present invention is not limited to the embodiments described therein, and various modifications and improvements can be made, which will be obvious to those skilled in the art.

[0135] For example, in the above implementation, LTM fast recovery is a prerequisite, but LTM fast recovery is not necessarily a prerequisite. That is to say, it is not limited to LTM fast recovery, but the masterKeyUpdate indication can also be applied in LTM cell switch.

[0136] For example, in the above description, configure, activate, update, indicate, enable, specify, and select can be used interchangeably. Similarly, link, associate, correspond, and map can be used interchangeably, as can allocate, assign, monitor, and map.

[0137] Furthermore, specific, dedicated, UE specific, and UE dedicated can be used interchangeably. Similarly, common, shared, group-common, UE common, and UE shared can also be used interchangeably.

[0138] The block structure diagram used in the description of the above embodiments ( Figure 3 , Figure 4 The diagram illustrates blocks organized by function. These functional blocks (structural units) are implemented through any combination of at least one of hardware and software. Furthermore, there are no particular limitations on the implementation method of each functional block. That is, each functional block can be implemented using a single device that is physically or logically combined, or by directly or indirectly (e.g., using wired, wireless, etc.) connecting two or more physically or logically separate devices. Functional blocks can also be implemented by combining software within the aforementioned single or multiple devices.

[0139] The functions include judgment, decision, determination, calculation, calculation, processing, derivation, investigation, search, confirmation, receiving, sending, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assigning, but are not limited to these. For example, the functional block (structural part) that performs the sending function is called the transmitting unit or transmitter. In short, as mentioned above, there are no particular limitations on the implementation method.

[0140] Furthermore, the aforementioned gNB 100 and UE 200 (the device) can also function as a computer for processing the wireless communication method disclosed herein. Figure 14 This is a diagram illustrating an example of the hardware structure of the device. (As shown...) Figure 14 As shown, the device can also be configured as a computer device including a processor 1001, a memory 1002, a storage device 1003, a communication device 1004, an input device 1005, an output device 1006, and a bus 1007.

[0141] Furthermore, in the following description, the term "device" can be replaced with "circuit," "device," "unit," etc. The hardware structure of the device can be configured as either a device comprising one or more of the illustrated components, or a device without any components.

[0142] The functional blocks of the device (refer to) Figure 3 , Figure 4 This can be achieved through any hardware element or combination of hardware elements in the computer device.

[0143] In addition, the functions of the device are implemented by reading predetermined software (programs) into hardware such as processor 1001 and memory 1002, so that processor 1001 performs calculations and controls communication of communication device 1004 or controls at least one of reading and writing data in memory 1002 and storage device 1003.

[0144] The processor 1001 controls the computer as a whole by instructing the operating system to operate. The processor 1001 may also be a central processing unit (CPU) that includes interfaces with peripheral devices, control devices, arithmetic units, registers, etc.

[0145] Furthermore, the processor 1001 reads programs (program code), software modules, data, etc., from at least one direction of memory 1002 in the storage device 1003 and the communication device 1004, and performs various processes accordingly. The program is used to cause the computer to perform at least a portion of the actions described in the above embodiments. Moreover, the various processes described above can be executed by one processor 1001, or by two or more processors 1001 simultaneously or sequentially. The processor 1001 can also be implemented using one or more chips. Furthermore, the program can also be transmitted from a network via a telecommunications line.

[0146] The memory 1002 is a computer-readable recording medium, and may be composed of at least one of the following: read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and random access memory (RAM). The memory 1002 may be referred to as a register, cache, main memory (main storage device), etc. The memory 1002 may store programs (program code), software modules, etc., capable of executing the methods according to an embodiment of this disclosure.

[0147] Storage device 1003 is a computer-readable recording medium, and may be composed of at least one of the following: optical discs such as CD-ROM (Compact Disc ROM), hard disk drives, floppy disks, magneto-optical discs (e.g., compact discs, digital multipurpose discs, Blu-ray discs), smart cards, flash memory (e.g., cards, sticks, key drives), floppy disks, magnetic stripes, etc. Storage device 1003 may also be referred to as an auxiliary storage device. The aforementioned recording medium may, for example, be a database, server, or other suitable media that includes at least one of memory 1002 and storage device 1003.

[0148] The communication device 1004 is hardware (transceiver) used for communication between computers via at least one of a wired network and a wireless network, and is also known as a network device, network controller, network card, communication module, etc.

[0149] The communication device 1004 may also be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc., to realize at least one of frequency division duplex (FDD) and time division duplex (TDD).

[0150] Input device 1005 is an input device that accepts input from external sources (e.g., keyboard, mouse, microphone, switch, button, sensor, etc.). Output device 1006 is an output device that performs output to external sources (e.g., display, speaker, LED, etc.). Furthermore, input device 1005 and output device 1006 can also be integrated (e.g., a touch panel).

[0151] Furthermore, devices such as processor 1001 and memory 1002 are connected via bus 1007 for communicating information. Bus 1007 can be configured as a single bus or as different buses between devices.

[0152] Furthermore, the device can 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), and a field-programmable gate array (FPGA), which can be used to implement some or all of the functional blocks. For example, the processor 1001 can also be implemented using at least one of these hardware components.

[0153] Furthermore, the notification of information is not limited to the forms / implementations described in this disclosure, and other methods may also be used. For example, information notification may be implemented through 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 combinations thereof. Additionally, RRC signaling may also be referred to as an RRC message, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, etc.

[0154] The various forms / implementations described in this disclosure can also be applied to systems utilizing LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER 3G, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system (5G), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (x being, 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 The system may include at least one of 802.20, Ultra-Wideband (UWB), Bluetooth (registered trademark), other suitable systems, and next-generation systems based on these systems. Alternatively, multiple systems may be combined (e.g., a combination of at least one of LTE and LTE-A with 5G).

[0155] The processing procedures, timing, and flow of the various forms / implementations described in this disclosure may be changed in order, provided there is no contradiction. For example, the elements of various steps are indicated using an illustrative order in the methods described in this disclosure, but are not limited to the specific order indicated.

[0156] In this disclosure, certain actions performed by the base station are sometimes also performed by its upper node, depending on the circumstances. In a network consisting of one or more network nodes having a base station, it is obvious that various actions performed to communicate with a terminal can be performed by at least one of the base station and other network nodes besides the base station (e.g., considering an MME or S-GW, but not limited to these). The above illustration depicts a case where there is only one other network node besides the base station, but it can also be a combination of multiple other network nodes (e.g., an MME and an S-GW).

[0157] It can output information and signals (information, etc.) from a higher (or lower) level to a lower (or higher) level. It can also input and output through multiple network nodes.

[0158] Input and output information can be stored in a specific location (e.g., memory) or managed using a management table. Input and output information can be overwritten, updated, or appended. Output information can also be deleted. Input information can also be sent to other devices.

[0159] The determination can be made by the value represented by 1 bit (0 or 1), by a Boolean value (Boolean: true or false), or by comparing numerical values ​​(e.g., comparing with a predetermined value).

[0160] The various forms / implementations described in this disclosure can be used individually or in combination, and can be switched depending on the execution. Furthermore, the notification of predetermined information (e.g., a "It is X" notification) is not limited to being explicit, but can also be implicit (e.g., not notifying the predetermined information).

[0161] Software, whether called software, firmware, middleware, microcode, hardware description language, or by other names, should be broadly interpreted as referring to commands, command sets, code, code segments, program code, programs, subroutines, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc.

[0162] In addition, software, commands, information, etc., can be sent and received via a transmission medium. For example, when software is sent from a webpage, server, or other remote source using at least one of wired technologies (coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL) etc.) and wireless technologies (infrared, microwave, etc.), at least one of these wired and wireless technologies is included within the definition of a transmission medium.

[0163] The information, signals, etc., described in this disclosure can also be represented using any of a variety of different technologies. For example, the data, commands, instructions, information, signals, bits, symbols, chips, etc., that may be involved in the above description as a whole can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or photons, or any combination of these.

[0164] Furthermore, the terms used in this disclosure and those necessary for understanding this disclosure may be replaced with terms that have the same or similar meanings. For example, at least one of the channel and symbol may also be a signal (signaling). Additionally, a signal may also be a message. Furthermore, a component carrier (CC) may also be referred to as a carrier frequency, cell, frequency carrier, etc.

[0165] The terms “system” and “network” as used in this disclosure are used interchangeably.

[0166] Furthermore, the information, parameters, etc., described in this disclosure can be represented using absolute values, relative values ​​to predetermined values, or other corresponding information. For example, wireless resources can be indicated using indexes.

[0167] The names used for the above parameters are non-limiting in any respect. Furthermore, the formulas, etc., using these parameters may sometimes differ from those explicitly disclosed in this disclosure. Various channels (e.g., PUCCH, PDCCH, etc.) and information elements can be identified by any appropriate name, and therefore the various names assigned to these channels and information elements are non-limiting in any respect.

[0168] In this disclosure, the terms "Base Station (BS)," "wireless 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" are used interchangeably. Sometimes, terms such as macro cell, small cell, femtocell, and picocell are also used to refer to base stations.

[0169] 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 also provide communication services through the base station subsystem (e.g., a small indoor base station (Remote Radio Head: RRH)).

[0170] Terms such as “cell” or “sector” refer to a portion or the entire coverage area of ​​at least one of the base stations and base station subsystems that provide communication services within that coverage area.

[0171] In this disclosure, the base station sending information to the terminal can also be replaced by the base station instructing the terminal on information-based control / actions.

[0172] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," and "terminal" are used interchangeably.

[0173] For mobile stations, those skilled in the art sometimes also use the following terms: 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, handheld device, user agent, mobile client, client, or some other appropriate terms.

[0174] At least one of the base station and mobile station can also be referred to as a transmitting device, receiving device, communication device, etc. Furthermore, at least one of the base station and mobile station can also be a device mounted on a mobile body, the mobile body itself, etc. The mobile body can be a vehicle (e.g., a car, an airplane, etc.), a mobile body moving in an unmanned manner (e.g., a drone, an autonomous vehicle, etc.), or a robot (humanized or unmanned). In addition, at least one of the base station and mobile station also includes devices that do not necessarily move during communication. For example, at least one of the base station and mobile station can be an IoT (Internet of Things) device such as a sensor.

[0175] Furthermore, the base station in this disclosure can also be replaced by a mobile station (user terminal, hereinafter the same). For example, various forms / implementations of this disclosure can also be applied to structures that replace communication between the base station and the mobile station with communication between multiple mobile stations (e.g., also referred to as D2D (Device-to-Device), V2X (Vehicle-to-Everything), etc.). In this case, the structure can also be configured such that the mobile station has the functions of the base station. In addition, terms such as "uplink" and "downlink" can also be replaced with terms corresponding to communication between terminals (e.g., "side"). For example, uplink channel, downlink channel, etc. can also be replaced with side channel (or side link).

[0176] Similarly, the mobile station in this disclosure can be replaced by a base station. In this case, the base station can also be configured to have the functions of a mobile station.

[0177] A wireless frame can consist of one or more frames in the time domain. Each frame in the time domain is called a subframe. A subframe can also consist of one or more time slots in the time domain. A subframe can be a fixed duration (e.g., 1 ms) independent of the parameter set (numerology).

[0178] A parameter set can be communication parameters applied to at least one of the transmission and reception of a signal or channel. For example, a parameter set can represent at least one of the following: Subcarrier Spacing (SCS), bandwidth, symbol length, cyclic prefix length, Transmission Time Interval (TTI), number of symbols per TTI, radio frame structure, specific filtering processing performed by the transceiver in the frequency domain, and specific windowing processing performed by the transceiver in the time domain.

[0179] In the time domain, a time slot can be composed of one or more symbols (OFDM (Orthogonal Frequency Division Multiplexing) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols, etc.). A time slot can be a time unit based on a set of parameters.

[0180] A time slot can contain multiple mini-time slots. Each mini-time slot can consist of one or more symbols in the time domain. Additionally, a mini-time slot can also be called a sub-time slot. A mini-time slot can consist of fewer symbols than a time slot. PDSCH (or PUSCH) transmitted in time units larger than mini-time slots can be called PDSCH (or PUSCH) mapping type (type) A. PDSCH (or PUSCH) transmitted using mini-time slots can be called PDSCH (or PUSCH) mapping type (type) B.

[0181] Radio frames, subframes, time slots, mini-time slots, and symbols all represent time units for transmitting signals. Radio frames, subframes, time slots, mini-time slots, and symbols can also be referred to by their respective alternative names.

[0182] For example, a single subframe can be called a Transmission Time Interval (TTI), multiple consecutive subframes can also be called a TTI, and a single time slot or a single mini-time slot can also be called a TTI. In other words, at least one of a subframe or TTI can be a subframe (1ms) in existing LTE, a period shorter than 1ms (e.g., 1-13 symbols), or a period longer than 1ms. Furthermore, the unit representing TTI can also be called a time slot, mini-time slot, etc., instead of a subframe.

[0183] Here, TTI refers, for example, to the smallest unit of time for scheduling in wireless communication. For instance, in an LTE system, the base station schedules the allocation of radio resources (bandwidth, transmit power, etc., available to each user terminal) in units of TTI. However, the definition of TTI is not limited to this.

[0184] The Time Interval (TTI) can be a unit of time for transmitting channel-coded data packets (transmission blocks), code blocks, codewords, etc., or it can be a processing unit such as scheduling or link adaptation. Furthermore, when a TTI is given, the actual time interval (e.g., the number of symbols) that the transmission block, code block, codeword, etc., are mapped to can be shorter than that TTI.

[0185] Furthermore, when one time slot or one mini time slot is referred to as a TTI, more than one TTI (i.e., more than one time slot or more than one mini time slot) can become the minimum time unit for scheduling. In addition, the number of time slots (mini time slots) constituting the minimum time unit for scheduling can also be controlled.

[0186] A TTI with a duration of 1ms can also be called a normal TTI (TTI in LTE Rel.8-12), a long TTI, a normal subframe, a long subframe, or a time slot. A TTI shorter than a normal TTI can also be called a shortened TTI, a short TTI, a partial or fractional TTI, a shortened subframe, a short subframe, a mini time slot, a sub-time slot, or a time slot.

[0187] Furthermore, for long TTIs (e.g., normal TTIs, subframes, etc.), they can be replaced with TTIs with a duration of more than 1ms, and for short TTIs (e.g., shortened TTIs, etc.), they can be replaced with TTIs with a duration of less than that of long TTIs but more than 1ms.

[0188] A resource block (RB) is a unit of resource allocation in both the time and frequency domains. In the frequency domain, it can contain one or more consecutive subcarriers. The number of subcarriers contained in an RB can be the same regardless of the parameter set, for example, it can be 12. The number of subcarriers contained in an RB can also be determined based on the parameter set.

[0189] In addition, the time domain of an RB can contain one or more symbols, which can be a time slot, a mini time slot, a subframe, or a TTI in length. A TTI, a subframe, etc., can each be composed of one or more resource blocks.

[0190] In addition, one or more RBs can also be called Physical Resource Block (PRB), Sub-Carrier Group (SCG), Resource Element Group (REG), PRB pair, RB pair, etc.

[0191] In addition, a resource block can consist of one or more resource elements (REs). For example, one RE can be a radio resource area consisting of one subcarrier and one symbol.

[0192] The Bandwidth Part (BWP) (also known as partial bandwidth, etc.) can represent a subset of contiguous common resource blocks (RBs) used for a certain parameter set in a given carrier. Here, common RBs can be determined by indexing RBs based on a common reference point of that carrier. PRBs can be defined and numbered within a BWP.

[0193] A BWP can include a UL BWP and a DL BWP. One or more BWPs can be set for a UE within a single carrier.

[0194] At least one of the configured BWPs can be active, and the UE may not intend to transmit or receive predetermined signals / channels outside of the active BWP. Furthermore, the terms "cell," "carrier," etc., used in this disclosure can be replaced with "BWP."

[0195] The structures of radio frames, subframes, time slots, mini-time slots, and symbols described above are merely illustrative. For example, the number of subframes contained in a radio frame, the number of time slots in each subframe or radio frame, the number of mini-time slots contained within a time slot, the number of symbols and RBs contained in a time slot or mini-time slot, the number of subcarriers contained in an RB, the number of symbols in a TTI, the symbol length, the cyclic prefix (CP) length, etc., can be varied in many ways.

[0196] The terms “connected,” “coupled,” or any variations thereof are intended to indicate any direct or indirect connection or combination between two or more elements, including cases where there is one or more intermediate elements between the two elements that are “connected” or “coupled.” The combination or connection between elements can be physical, logical, or a combination of these. For example, “access” can be used instead of “connected.” In the context of this disclosure, it can be understood that two elements are “connected” or “coupled” to each other using at least one of one or more wires, cables, and printed electrical connections, and, as some non-limiting and non-inclusive examples, they are “connected” or “coupled” to each other using electromagnetic energy with wavelengths in the wireless frequency domain, microwave region, and light (both visible and invisible) region.

[0197] The reference signal can be simply called the Reference Signal (RS), or, depending on the standard applied, the pilot signal.

[0198] As used in this disclosure, the word "based on" does not mean "based on only" unless otherwise expressly stated. In other words, the word "based on" means both "based on only" and "based on at least".

[0199] Alternatively, the "unit" in the structure of the above devices can be replaced with "section", "circuit", "equipment", etc.

[0200] Any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not necessarily limit the number or order of these elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Therefore, references to "first" and "second" do not imply that only two elements can be used there, or that in some form the first element must precede the second element.

[0201] When the terms "include," "including," and their variations are used in this disclosure, these terms, like the term "comprising," imply inclusion. Furthermore, the term "or" as used in this disclosure does not refer to XOR.

[0202] In this disclosure, for example, in cases where articles are added through translation, such as in English (e.g., a, an, and the), this disclosure may also include cases where the noun following these articles is in a plural form.

[0203] As used in this disclosure, terms such as "determining" and "determining" sometimes encompass a variety of actions. For example, "determining" or "determining" may include actions such as judging, calculating, computing, processing, deriving, investigating, searching (e.g., searching in a table, database, or other data structure), and ascertaining, which are considered as actions of "determining" or "determining." Furthermore, "determining" or "determining" may include actions such as receiving (e.g., receiving information), transmitting (e.g., sending information), inputting, outputting, and accessing (e.g., accessing data in memory), which are considered as actions of "determining" or "determining." Additionally, "determining" or "determining" may include actions such as resolving, selecting, choosing, establishing, and comparing, which are considered as actions of "determining" or "determining." In other words, "judgment" and "decision" can include matters that are considered as having been "judged" or "decided". In addition, "judgment (decision)" can also be replaced by "assuming", "expecting", "considering", etc.

[0204] In this disclosure, the phrase "A and B are different" can mean "A and B are not the same." Furthermore, this phrase can also mean "A and B are each different from C." Terms such as "separate" and "combined" can also be interpreted in the same way as "different."

[0205] Figure 15 An example of the structure of vehicle 2001 is shown. For example... Figure 15 As shown, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a gear 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.

[0206] The drive unit 2002 may be composed of, for example, an engine, a motor, or a hybrid powertrain of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a steering wheel), configured to steer at least one of the front and rear wheels based on user-operated steering wheel movements. The electronic control unit 2010 consists of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals from various sensors 2021 to 2027 present in the vehicle are input to the electronic control unit 2010. The electronic control unit 2010 may also be referred to as an ECU (Electronic Control Unit).

[0207] The signals from various sensors 2021 to 2028 include current signals from current sensor 2021 that senses the current of the motor, speed signals of the front and rear wheels obtained by speed sensor 2022, air pressure signals of the front and rear wheels obtained by air pressure sensor 2023, vehicle speed signals obtained by vehicle speed sensor 2024, acceleration signals obtained by acceleration sensor 2025, accelerator pedal input signals obtained by accelerator pedal sensor 2029, brake pedal input signals obtained by brake pedal sensor 2026, gear lever operation signals obtained by gear lever sensor 2027, and detection signals obtained by object detection sensor 2028 for detecting obstacles, vehicles, pedestrians, etc.

[0208] The Information Service Unit 2012 consists of various devices such as a car navigation system, audio system, speakers, television, and radio, which provide (output) various information such as driving information, traffic information, and entertainment information, and one or more ECUs that control these devices. The Information Service Unit 2012 uses information obtained from external devices via communication modules 2013, etc., to provide various multimedia information and multimedia services to the occupants of vehicle 1.

[0209] The Information Services Department 2012 may include input devices that accept input from external sources (e.g., keyboard, mouse, microphone, switch, button, sensor, touch panel, etc.) and output devices that implement output to external sources (e.g., monitor, speaker, LED light, touch panel, etc.).

[0210] The Driver Assistance System 2030 comprises various devices used to prevent accidents or reduce driver workload, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning devices (e.g., GNSS), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps), gyroscope systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System)), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. Furthermore, the Driver Assistance System 2030 transmits and receives various information via the communication module 2013 to achieve driver assistance or autonomous driving functions.

[0211] The communication module 2013 can communicate with the microprocessor 2031 and the components of the vehicle 1 via the communication port. For example, the communication module 2013 can send and receive data with the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, gear shift lever 2006, left and right front wheels 2007, left and right rear wheels 2008, axle 2009, microprocessor 2031 in the electronic control unit 2010, memory (ROM, RAM) 2032, and sensors 2021 to 2028 in the vehicle 2001 via the communication port 2033.

[0212] The communication module 2013, controlled by the microprocessor 2031 of the electronic control unit 2010, is a communication device capable of communicating with external devices. For example, it can transmit and receive various types of information with external devices via wireless communication. The communication module 2013 can be located inside or outside the electronic control unit 2010. External devices can be, for example, base stations, mobile stations, etc.

[0213] The communication module 2013 can wirelessly transmit to an external device at least one of the signals input to the electronic control unit 2010 from the various sensors 2021-2028, information obtained based on those signals, and information obtained via the information service unit 2012 based on input from an external source (user). The electronic control unit 2010, the various sensors 2021-2028, and the information service unit 2012 can also be referred to as input units that receive input. For example, the PUSCH transmitted by the communication module 2013 can contain information based on the aforementioned input.

[0214] The communication module 2013 receives various information (traffic information, signal information, vehicle-to-vehicle information, etc.) sent from external devices and displays it on the information service unit 2012 provided by the vehicle. The information service unit 2012 can also be referred to as an output unit for outputting information (for example, outputting information to devices such as displays and speakers based on the PDSCH received by the communication module 2013 (or data / information decoded from the PDSCH). In addition, the communication module 2013 stores the various information received from external devices in a memory 2032 available to the microprocessor 2031. The microprocessor 2031 can also control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, gear lever 2006, left and right front wheels 2007, left and right rear wheels 2008, axles 2009, sensors 2021 to 2028, etc., provided by the vehicle 2001 based on the information stored in the memory 2032.

[0215] The present disclosure has been described in detail above, but it will be 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 as modifications and variations without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the present disclosure is for illustrative purposes only and is not intended to be limiting.

[0216] (Postscript)

[0217] The aforementioned disclosure can also be expressed as follows.

[0218] The first feature is a terminal comprising: a control unit that performs cell handover in the event of a failure of low-level mobility control; a transmission unit that sends a connection reset request when the cell handover is not to a candidate cell that follows the mobility control; and a receiving unit that receives a message containing an update instruction for key information to ensure security with the network, wherein the control unit updates the key information when it receives the update instruction during the cell handover.

[0219] The second feature is that, in the first feature, if the control unit does not receive the update instruction during the cell handover, it continues to use the entity of the packet data aggregation protocol layer.

[0220] The third feature is that, in the first or second feature, the control unit continues to use the entity with the signaling radio bearer as the target.

[0221] The fourth feature is that, in features 1 to 3, the receiving unit receives the update instruction associated with a list of identification information of the candidate cells or a list of additions or changes to the candidate cells.

[0222] Label Explanation

[0223] 10 Wireless Communication Systems

[0224] 20 NG-RAN

[0225] 100 gNB

[0226] 110 Wireless Communications Department

[0227] 120 Switching Processing Unit

[0228] 130 Measurement Setting Section

[0229] 140 Control Department

[0230] 200 UE

[0231] 210 Wireless Communications Department

[0232] 220 Measurement Reporting Department

[0233] 230 Switching Execution Unit

[0234] 240 Control Department

[0235] 1001 processor

[0236] 1002 Memory

[0237] 1003 Storage device

[0238] 1004 Communication device

[0239] 1005 Input Device

[0240] 1006 Output Device

[0241] 1007 bus

[0242] Vehicle 2001

[0243] 2002 Drive Unit

[0244] 2003 Steering Unit

[0245] 2004 Accelerator Pedal

[0246] 2005 Brake Pedal

[0247] 2006 gearshift lever

[0248] Front wheels around 2007

[0249] 2008 rear wheels (left and right)

[0250] 2009 axle

[0251] 2010 Electronic Control Department

[0252] 2012 Information Service Department

[0253] 2013 Communication Module

[0254] 2021 Current Sensor

[0255] 2022 Speed ​​Sensor

[0256] 2023 Barometric Pressure Sensor

[0257] 2024 vehicle speed sensor

[0258] 2025 Accelerometer

[0259] 2026 Brake Pedal Sensor

[0260] 2027 Gearshift sensor

[0261] 2028 Object Detection Sensor

[0262] 2029 Accelerator Pedal Sensor

[0263] 2030 Driver Assistance Systems Department

[0264] 2031 microprocessor

[0265] 2032 Memory (ROM, RAM)

[0266] 2033 Communication Port

Claims

1. A terminal, comprising: The control unit performs cell handover in the event of failure of low-level mobility control. The transmitting unit, when not handing over to a candidate cell that complies with the mobility control, sends a connection reset request; and The receiving unit receives a message containing an update instruction for key information used to ensure security with the network. When the control unit receives the update instruction during the cell handover, it updates the key information.

2. The terminal according to claim 1, wherein, If the control unit does not receive the update instruction during the cell handover, it continues to use the entity of the packet data aggregation protocol layer.

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

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

5. A wireless communication system comprising a terminal and a wireless base station, wherein, The wireless base station includes a transmitting unit that sends a message to the terminal containing an update instruction for key information used to ensure security with the network. The terminal has: The control unit performs cell handover in the event of failure of low-level mobility control. The transmitting unit sends a connection reset request when it is not a handover to a candidate cell that complies with the mobility control. as well as The receiving unit receives a message containing the update instruction. When the control unit receives the update instruction during the cell handover, it updates the key information.

6. A wireless communication method in a terminal, comprising the following steps: In the event of failure of low-level mobility control, a cell handover is performed; If the handover is not to a candidate cell that complies with the mobility control, a connection reset request is sent; Receive a message containing an update instruction for key information used to ensure security with the network; as well as If the update instruction is received during the cell handover, the key information is updated.

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