Security procedures for subsequent LTM and failover

Abstract

An apparatus for a user equipment is provided, comprising at least one processor; and at least one memory including instructions that, when executed by the at least one processor, cause the apparatus to: receive, via media access control layer signaling, a next-hop chain counter value from a distributed unit of an access node of the serving cell of the user equipment for a subsequent layer 1 / layer 2 triggered mobility procedure; and, based on the received next-hop chain counter value, determine a security key generation procedure to be applied to the subsequent layer 1 / layer 2 triggered mobility procedure.

Description

Technical Field

[0001] Various example embodiments generally relate to the field of wireless communications. Some example embodiments relate to security procedures for subsequent Layer 1 / Layer 2 triggered mobility (LTM) and also for fault recovery during the LTM process. Background Technology

[0002] In wireless communications, a seamless handover with security provisions is desired. In 5G, the handover process typically involves User Equipment (UE), base stations (such as gNBs), and Access and Mobility Management Functions (AMFs). The handover is triggered when a UE moves from its current gNB to another gNB, during which time the UE and gNB can be configured to perform mutual authentication and key negotiation. Summary of the Invention

[0003] The present invention is provided to present, in a simplified form, the selection of concepts further described below in the detailed embodiments. The present invention is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0004] The exemplary embodiments of this disclosure enable the forwarding of next-hop chain counter values ​​to the UE without using radio resource control reconfiguration. This and other benefits can be realized through the features of the independent claims. Further exemplary embodiments are provided in the dependent claims, description, and drawings.

[0005] According to a first aspect, an apparatus for a user equipment is disclosed. The apparatus may include: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receive, via media access control layer signaling, a next-hop chain counter value from a distributed unit of an access node of the serving cell of the user equipment for a subsequent layer 1 / layer 2 triggered mobility procedure; and, based on the received next-hop chain counter value, determine a security key generation process to be applied to the subsequent layer 1 / layer 2 triggered mobility procedure.

[0006] According to an example embodiment of the first aspect, the next-hop chain counter value is received in at least one of the individual messages received from the distributed unit before the cell handover command or prior to the cell handover command.

[0007] According to an example embodiment of the first aspect, the apparatus is further configured to: receive, via media access control layer signaling, an indication from a distributed unit of the access node regarding whether a received next-hop chain counter value will be used by the user equipment for intra-access node handover; and, based on the received indication, determine a security key generation process for intra-access node handover.

[0008] According to an example embodiment of the first aspect, at least one of the cell handover command or individual message further includes an indication of whether to use the received next-hop chain counter value for intra-access node handover.

[0009] According to an example embodiment of the first aspect, the apparatus is further configured to: in the event of radio link failure recovery, receive, via media access control layer signaling, an instruction from the distributed unit of the access node to use one of the following: the latest security key of the serving cell, or a new security key generated for the serving cell; and determine a security key generation process based on the received instruction for radio link failure recovery.

[0010] According to an example embodiment of the first aspect, at least one of the cell handover command or individual message further includes an indication to use either the latest security key of the serving cell or a new security key generated for the serving cell in the event of a radio link failure recovery.

[0011] According to an example embodiment of the first aspect, the media access control signaling includes a media access control (MAC) control element.

[0012] According to an example embodiment of the first aspect, the apparatus is further configured to: detect a radio link failure; select a candidate cell for fault recovery based on the detected radio link failure; and initiate a subsequent mobility procedure to the selected candidate cell for fault recovery, wherein the security key for the mobility procedure is updated based on a determined security key generation procedure.

[0013] According to a second aspect, a method is disclosed. The method may include: receiving a next-hop chain counter value for a subsequent Layer 1 / Layer 2 triggered mobility procedure from a distributed unit of an access node of a serving cell of a user equipment via media access control layer signaling; and determining a security key generation process to be applied to the subsequent Layer 1 / Layer 2 triggered mobility procedure based on the received next-hop chain counter value.

[0014] According to an example embodiment of the second aspect, the next-hop chain counter value is received in at least one of the individual messages received from the distributed unit before the cell handover command or prior to the cell handover command.

[0015] According to an example embodiment of the second aspect, the method may include: receiving, via media access control layer signaling, an indication from the distributed unit of the access node whether a received next-hop chain counter value will be used by the user equipment for intra-access node handover; and determining a security key generation process for the next intra-access node handover based on the received indication.

[0016] According to an example embodiment of the second aspect, at least one of the cell handover command or individual message further includes an indication of whether to use the received next-hop chain counter value for intra-access node handover.

[0017] According to an example embodiment of the second aspect, the method further includes: in the event of radio link failure recovery, receiving, via media access control layer signaling, an instruction from the distributed unit of the access node to use one of the following: the latest security key of the serving cell, or a new security key generated for the serving cell; and determining a security key generation process based on the received instruction for radio link failure recovery.

[0018] According to an example embodiment of the second aspect, at least one of the cell handover command or individual message further includes an indication to use either the latest security key of the serving cell or a new security key generated for the serving cell in the event of a radio link failure recovery.

[0019] According to an example embodiment of the second aspect, the media access control signaling includes a media access control (MAC) control element.

[0020] According to an example embodiment of the second aspect, the method includes: detecting a radio link failure; selecting a candidate cell for fault recovery based on the detected radio link failure; and initiating a subsequent mobility procedure to the selected candidate cell for fault recovery, wherein the security key for the mobility procedure is updated based on a determined security key generation procedure.

[0021] According to a third aspect, an apparatus for a distributed unit is disclosed. The apparatus may include: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: receive a message including a next-hop chain counter value from a centralized unit of an access node; update a next-hop chain counter value stored at a distributed unit of the access node associated with the serving cell of a user equipment, based on the received next-hop chain counter value; and transmit the updated next-hop chain counter value to the user equipment via media access control layer signaling for subsequent layer 1 / layer 2 triggered mobility procedures.

[0022] According to an example embodiment of the third aspect, the message includes at least one of the following: a user equipment context establishment request, or a user equipment context modification request.

[0023] According to an example embodiment of the third aspect, the apparatus is further configured to: receive from the centralized unit of the access node an indication of whether the received next-hop chain counter value will be used by the user equipment for handover within the access node; and transmit the indication to the user equipment via media access control layer signaling.

[0024] According to an example embodiment of the third aspect, the apparatus is further configured to: receive from the centralized unit of the access node an instruction for the user equipment to use one of the following for radio link failure recovery: the latest security key of the serving cell, or the generation of a new security key for the serving cell; and transmit the received instruction to the user equipment via media access control signaling.

[0025] According to an example embodiment of the third aspect, the Media Access Control (MAC) layer signaling includes a Media Access Control (MAC) element.

[0026] According to an example embodiment of the third aspect, the media access control layer signaling includes at least one of the following: a cell handover command; or a separate message preceding the cell handover command transmitted by the distributed unit.

[0027] According to a fourth aspect, a method is disclosed. The method may include: receiving a message including a next-hop chain counter value from a centralized unit of an access node; updating a next-hop chain counter value stored at a distributed unit of the access node associated with the serving cell of a user equipment based on the received next-hop chain counter value; and transmitting the updated next-hop chain counter value to the user equipment via media access control layer signaling for subsequent layer 1 / layer 2 triggered mobility procedures.

[0028] According to an example embodiment of the fourth aspect, the message includes at least one of the following: a user equipment context establishment request or a user equipment context modification request.

[0029] According to an example embodiment of the fourth aspect, the method includes: receiving an indication from a centralized unit of the access node whether a received next-hop chain counter value will be used by the user equipment for handover within the access node; and transmitting the indication to the user equipment via media access control layer signaling.

[0030] According to an example embodiment of the fourth aspect, the method includes: receiving from a centralized unit of an access node an indication for a user equipment to use one of the following for radio link failure recovery: an updated security key for the serving cell, or the generation of a new security key for the serving cell; and transmitting the received indication to the user equipment via media access control signaling.

[0031] According to an example embodiment of the fourth aspect, the Media Access Control (MAC) layer signaling includes a Media Access Control (MAC) element.

[0032] According to an example embodiment of the fourth aspect, the media access control layer signaling includes at least one of the following: a cell handover command; or a separate message preceding the cell handover command transmitted by the distributed unit.

[0033] According to a fifth aspect, an apparatus for a centralized unit is disclosed. The apparatus may include: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to at least: determine that a next-hop link counter value stored at the centralized unit of an access node has been updated; and transmit a message including the determined next-hop link counter value to a distributed unit of the access node associated with the serving cell of a user equipment, the next-hop link counter value being forwarded by the distributed unit to the user equipment for subsequent L1 / L2 triggered mobility procedures.

[0034] According to an example embodiment of the fifth aspect, the apparatus is further configured to: determine whether the next-hop chain counter value will be used by the user equipment for intra-access node handover; and based on the determination, transmit an indication to the distributed unit regarding whether the next-hop chain counter value will be used by the user equipment for intra-access node handover.

[0035] According to an example embodiment of the fifth aspect, the apparatus is further configured to: determine, in the event of a radio link failure recovery, that the user equipment uses either the latest security key of the serving cell or a new security key generated by the user equipment for the serving cell; and based on the determination, transmit to the distributed unit an instruction for the apparatus to use either the latest security key of the serving cell or a new security key generated for the serving cell in the event of a radio link failure recovery.

[0036] According to an example embodiment of the fifth aspect, at least one of the following is transmitted in at least one of the User Equipment Context Establishment Request Message or User Equipment Context Modification Request Message: a next-hop chain counter value, an indication of whether to use the next-hop chain counter for handover within the next access node, or the use of a latest key or a newly generated key.

[0037] According to a sixth aspect, a method is disclosed. The method includes: determining that a next-hop chain counter value stored at a centralized unit of an access node has been updated; and transmitting a message including the determined next-hop chain counter value to a distributed unit of the access node associated with the serving cell of a user equipment, the next-hop chain counter value being forwarded by the distributed unit to the user equipment for subsequent L1 / L2 triggered mobility procedures.

[0038] According to an example embodiment of the sixth aspect, the method includes: determining whether the next-hop chain counter value will be used by the user equipment for intra-access node handover; and based on the determination, transmitting an indication to the distributed unit whether the next-hop chain counter value will be used by the user equipment for intra-access node handover.

[0039] According to an example embodiment of the sixth aspect, the method includes: in the event of a radio link failure recovery, determining that the user equipment will use one of the following: a latest security key for the serving cell, or a new security key generated by the user equipment for the serving cell; and based on the determination, transmitting to the distributed unit an instruction for the equipment to use one of the following in the event of a radio link failure recovery: the latest security key for the serving cell, or a new security key generated for the serving cell.

[0040] According to an example embodiment of the sixth aspect, at least one of the following is transmitted in at least one of the User Equipment Context Establishment Request Message or User Equipment Context Modification Request Message: a next-hop chain counter value, an indication of whether to use the next-hop chain counter for handover within the next access node, or the use of a latest key or a newly generated key.

[0041] According to a seventh aspect, an apparatus is disclosed. The apparatus may include components for performing methods as provided in the specification and / or claims according to the second, fourth, or sixth aspects or any of the example embodiments thereof.

[0042] According to the eighth aspect, a computer program, computer program product, or (non-transitory) computer-readable medium is disclosed. The computer program, computer program product, or (non-transitory) computer-readable medium may include instructions that, when executed by a device, cause the device to perform at least the method as provided in the specification and / or claims according to the second, fourth, or sixth aspect or any of the example embodiments thereof.

[0043] Therefore, exemplary embodiments of this disclosure can provide apparatus, methods, computer programs, computer program products, or computer-readable media for improving various aspects of wireless network sharing. Any exemplary embodiment may be combined with one or more other exemplary embodiments. These and other aspects of this disclosure will become apparent from the exemplary embodiments(s) described below. The subject matter of the independent claims is provided according to some aspects. Additional aspects are defined in the dependent claims. Attached Figure Description

[0044] The accompanying drawings are included to provide a further understanding of the exemplary embodiments and form part of this specification. They illustrate exemplary embodiments and, together with the specification, help to explain the exemplary embodiments. In the drawings: Figure 1 An example of a communication network is shown; Figure 2 An example of a device configured to practice one or more example embodiments is shown; Figure 3 Examples of signaling and operations used in subsequent LTM security procedures are shown; Figure 4 Another example of signaling and operations for subsequent LTM and fault recovery procedures is shown; Figure 5 An example of a method for the subsequent LTM safety process is shown.

[0045] Figure 6 An example of another method for the subsequent LTM safety process is shown.

[0046] In the accompanying drawings, the same reference numerals are used to denote the same parts. Detailed Implementation

[0047] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below, in conjunction with the drawings, is intended as a description of this example and is not intended to represent the only form in which this example can be constructed or utilized. This description illustrates the functionality of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functionality and sequence can be implemented through different examples.

[0048] Figure 1 An example of a communication network is shown. Communication network 100 may include one or more access nodes, such as access nodes 104, 106, and / or 108. Access nodes 104, 106, and 108 may be part of a radio access network (RAN) configured to enable mobile devices, represented throughout this specification by UE 102, to access communication services provided by core network (CN) 110. In conjunction with communication network 100, access nodes 104, 106, and 108 and core network 110 may be collectively referred to as the “network.” UE 102 may include user equipment, user nodes, mobile devices, etc. UE 102 may be configured to communicate with access nodes 104, 106, and / or 108 via a radio interface (which may also be referred to as an air interface). Access nodes 104, 106, and 108 may also be referred to as network devices.

[0049] The radio interface can be configured, for example, based on the 5G NR (New Radio) standard defined by the 3rd Generation Partnership Project (3GPP) or any future standard or technology (e.g., 6G). Access nodes 104, 106, and 108 can include, for example, fifth-generation access nodes (gNBs). Transmissions from the access nodes to UE 102 can be referred to as downlink (DL) transmissions. Transmissions from UE 102 to the access nodes can be referred to as uplink (UL) transmissions. Therefore, UE 102 can be configured to operate as a transmitter for uplink transmissions and a receiver for downlink transmissions. Access nodes 104, 106, and 108 can be configured to operate as a receiver for uplink transmissions and a transmitter for downlink transmissions. The communication network 100 can include a wireless communication network or a mobile communication network, such as a cellular communication network.

[0050] Core network 110 can utilize various network functions (NFs), including, for example, one or more user plane functions (UPFs) and one or more access and mobility management functions (AMFs). The UPF can be configured to handle the user data portion of a communication session. Therefore, the UPF can provide an interconnection point between the radio access network and the data network, configured to provide application services to UE 102 via core network 110 and the radio access network. The AMF can be configured (e.g., via an access node) to receive connection and session request related data from UE 102. The AMF can be configured to control connection and mobility management within communication network 100.

[0051] Access nodes 104, 106, and 108 can be configured to communicate with the UE via one or more cells. For example, access node 104 can be configured to serve the UE in cell 112. Access node 106 can be configured to serve the UE in cell 114. Access node 108 can be configured to serve the UE in cell 116. Access nodes can be configured to serve one or more cells, although... Figure 1 The diagram only depicts one cell associated with each access node. A cell can be configured to serve a UE in a specific geographic area using a specific radio frequency or a radio frequency range around the cell's center frequency. During the handover process, a specific cell can be referred to as the serving cell and the target cell. The serving cell can refer to the access node currently serving a particular UE and its associated cell. The UE can currently connect and communicate with the serving cell. The target cell can refer to the access node to which the UE is expected to be handed over during a mobility event, such as a handover triggered by mobility or network conditions. Once the handover is successfully completed, the target cell becomes the new serving cell for the UE, and the UE continues its communication with the network through this target cell.

[0052] The UE can be configured to perform measurements on neighboring (target) cells or serving cells for mobility purposes. The configured measurements can be, for example, L3 (Layer 3) measurements, which enable the network to make decisions regarding L3 handover, or L1 (Layer 1) measurements, which enable the network to make decisions regarding L1 / L2 (Layer 1 / Layer 2) triggered mobility (LTM). LTM is also known as lower-layer triggered mobility. The UE reports measurements to the network based on a measurement reporting configuration, which can be, for example, periodic or event-triggered. The network can make handover or cell handover decisions based on the reported measurements and command the UE to perform handover / cell handover to the selected target cell.

[0053] The communication network 100 can operate based on a protocol stack comprising multiple protocol layers. The protocol stack can be arranged based on the Open Systems Interconnection (OSI) model or a layer model of a specific standard (such as 3GPP 5G NR). As an example, the protocol stack may include a Serving Data Adaptation Protocol (SDAP) layer, which receives data from the application layer for transmission. The SDAP layer can be configured to exchange data with a Packet Data Convergence (PDCP) layer. The PDCP layer can be responsible for, for example, generating data bursts comprising one or more data packets based on data obtained from the SDAP layer.

[0054] The PDCP layer can provide data to one or more instances of the Radio Link Control (RLC) layer. Each RLC instance can be associated with a corresponding MAC instance of the Media Access Control (MAC) layer. The MAC layer can provide mapping between upper-layer logical channels(s) and physical-layer transport channels, handling the multiplexing and demultiplexing of MAC Service Data Units (SDUs). Furthermore, the MAC layer can provide error correction based on packet retransmission (e.g., according to the Hybrid Automatic Repeat Request (HARQ) procedure). The RLC and / or MAC layers can be referred to as Layer 2 (L2). Physically separated transport branches can be provided by the Physical (PHY) layer (also referred to as Layer 1 (L1)). Corresponding protocol stacks can be applied at access nodes 104, 106, 108, and UE 102. The UE can be configured to perform mobility measurements based on the lower layers of the protocol stack (e.g., RLC, MAC, and L1). The Radio Resource Control (RRC) layer of the protocol stack can be configured to manage the configuration, connection, and release of radio resources. The RRC layer can also be referred to as Layer 3. L1 and L3 measurements can include parameters related to wireless channel conditions, such as signal strength, signal-to-noise ratio (SNR), and channel quality indicator (CQI).

[0055] In a split access node architecture, a portion of the protocol layer can be implemented at the centralized unit (CU) of the access node, such as the gNB-CU, which can be configured to handle the upper layers of the protocol stack, such as SDAP and PDCP layers. Furthermore, the centralized unit can be configured to handle Radio Resource Control (RRC) operations. The centralized unit of the access node can be associated with one or more distributed units (DUs) of the access node (e.g., each as a control DU), such as the gNB-DU, which can be configured to handle the lower layers of the protocol stack, such as RLC, MAC, and L1. The radio units of the (multiple) distributed units can be configured to transmit data to / receive data from (multiple) UEs via radio interfaces. The centralized unit can be referred to as the central node, and the distributed units can be referred to as distributed nodes. The gNB-CU and gNB-DU can be connected via an F1 interface. Each DU and each CU can be associated with one or more cells of the gNB. The distributed unit located at the serving cell of the UE can be referred to as the serving DU. The centralized unit located at or associated with a DU located at the serving cell can be referred to as the serving CU.

[0056] The gNB can initiate the establishment of a context for communication between the UE and the network using an Initial UE Context Establishment message. For example, the gNB-CU can initiate this process by sending a UE Context Establishment Request message to the gNB-DU. If the gNB-DU successfully establishes the UE context, it can reply to the gNB-CU with a UE Context Establishment response. If no logical F1 connection is associated with the UE, it can establish the associated logical F1 connection as part of the process.

[0057] For example, a UE context establishment message may include the PDU session context, security key, mobility restriction list, UE radio capabilities, UE security capabilities, and other configured information. The F1 Application Protocol (F1AP) can be used to transmit UE context establishment messages. F1AP refers to the protocol used for transmitting and receiving data using the F1 interface.

[0058] When it is necessary to modify the established UE context (e.g., to establish, modify, and / or release radio resources), the gNB-CU can initiate an F1AP UE context modification request to the gNB-DU.

[0059] For secure handover, a key management scheme based on horizontal and vertical key derivation was designed. The access layer security context can be based on either horizontal or vertical key derivation. For both horizontal and vertical key derivation, PCI (Physical Cell Identifier) ​​and DL (Downlink) frequencies can be used. In horizontal key derivation, the previous key already used for key generation can be reused. In vertical key derivation, key refresh can be performed by using a new NH (Next Hop) parameter value. NH is the intermediate key used to derive the session key in vertical key derivation. Vertical key derivation is used to separate the key space for each RAN node. The NH value can be provided to the RAN node by the AMF. The vertical key generated by each RAN node can use the new NH value provided by the AMF. Therefore, the security domain can be separated from the previous RAN node. The main difference between these options (horizontal / vertical key derivation) is that forward security can be provided solely by vertical key derivation. In both options, the newly derived intermediate session key KgNB... It can become the new session key after the handover is complete. The key can refer to a security key, such as a session key.

[0060] The UE can be instructed on how to generate a key by indicating the NCC value to the UE after each cell change. The NCC value can be indicated by the gNB in ​​the handover command. However, in the case of LTM dynamic handover via MAC CE cell handover command, the candidate cell configuration can be reused after a cell change without a new RRC reconfiguration. In this case, the same NCC value will be used repeatedly, and only horizontal key derivation is possible. For security reasons, this should be avoided in order to provide new keys with new NH values ​​for different gNBs.

[0061] According to the example embodiment, the serving DU can be configured to transmit the next-hop chain counter (NCC) value to the UE via MAC layer signaling. The NCC can be defined according to the 3GPP specification: NCC is a counter associated with the NH, i.e., the number of key chains executed, which allows the UE to synchronize with the gNB and determine the next key chain. Whether the NH needs to be based on the current KeNB or a refreshed one depends on the specific requirements. The NCC value can be transmitted, for example, in a cell handover command. Alternatively, the NCC value can be transmitted in a dedicated separate message (such as in a MAC CE (control element)) before the cell handover command. Therefore, the NCC value can be indicated to the UE without an RRC reconfiguration or handover command. Furthermore, when the NCC is indicated to the UE before handover / cell handover, the UE can perform LTM recovery using the NCC value in the event of a radio link failure, where the handover / cell handover command may not be received by the UE.

[0062] In an example embodiment, the NCC value to be forwarded by the DU to the UE can be received by the DU from the CU during at least one of the following periods: a handover preparation process, or a path handover process. For example, the CU can be configured to transmit the NCC value to the DU in a DL transmission message. The DL transmission message may include at least one of, for example, a UE context establishment request or a UE context modification request. The NCC can be transmitted by the CU along with one or more additional indications to be forwarded to the UE. The one or more indications may be related to a security key deduction to be performed by the UE. Furthermore, the DU can be configured to forward the received indications to the UE via MAC layer signaling, such as in a MAC CE message that includes the NCC value.

[0063] According to an example embodiment, the UE can be configured to determine, based on an NCC value received from the serving DU via MAC layer signaling, which of the following security key generation procedures—for example, vertical or horizontal key derivation—to be applied to subsequent LTM mobility procedures. The MAC layer signaling may also include one or more indications related to the determination of the security key generation procedure, and the UE may also be configured to determine the security key generation procedure to be applied based on one or more indications.

[0064] Apart from Figure 1 In addition to or as alternatives to those shown, communication network 100 may include other network functions(s), network devices(s), or protocols(s). Network devices may be configured to implement one or more network functions. Although some embodiments have been described in the context of 5G, it should be understood that embodiments of this disclosure are not limited to this example network. Therefore, the example embodiments can be applied to any current or future communication network. Apparatus (e.g., UE 102 or access node 104) may include or be configured to implement one or more protocol layers described herein, for example, by means of software.

[0065] Figure 2 Examples of apparatuses configured to practice one or more exemplary embodiments are shown. Apparatus 200 may include: a mobile device (such as UE 102), or access nodes 104, 106, 108, an access point, a base station, a radio network node, or a subset thereof (e.g., a centralized or distributed unit of an access node), a network device, or generally any apparatus configured to implement the functionality described herein. In another embodiment, the apparatus is included in UE 102, access nodes 104, 106, 108, etc. The apparatus may be, for example, a chipset for a corresponding entity in a cellular communication network.

[0066] The device 200 may include at least one processor 202. The at least one processor 202 may include one or more of various processing devices, such as a coprocessor, microprocessor, controller, digital signal processor (DSP), processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), microcontroller units (MCUs), hardware accelerators, dedicated computer chips, etc.

[0067] The device 200 may also include at least one memory 204. Memory 204 may be configured to store, for example, computer program code, such as operating system software and application software. Memory 204 may include one or more volatile memory devices, one or more non-volatile memory devices, and / or combinations thereof. For example, memory may be embodied as a magnetic storage device (such as a hard disk drive, magnetic tape, etc.), an optical magnetic storage device, or a semiconductor memory (such as a mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.). An example of memory 204 as a (non-transitory) computer-readable medium is provided. As used herein, the term "non-transitory" is a limitation on the medium itself (i.e., tangible, not tactile), rather than a limitation on the persistence of data storage (e.g., RAM and ROM).

[0068] The device 200 may also include a communication interface 208 configured to enable the device 200 to transmit and / or receive information. The communication interface 208 may include an external communication interface, such as a radio interface between the UE 102 and (multiple) access nodes 104, 106, 108, or a communication interface (e.g., an F1 interface) between a centralized unit of an access node and (multiple) distributed units. The communication interface 208 may include one or more radio transmitters or receivers that may be coupled to one or more antennas or the device 200, or configured to be coupled to one or more antennas external to the device 200.

[0069] The device 200 may also include other components and / or functions, such as a user interface (not shown) including at least one input device and / or at least one output device. The input device may take various forms, such as a keyboard, a touchscreen, or one or more embedded control buttons. The output device may include, for example, a display, a speaker, etc.

[0070] When the device 200 is configured to perform certain functions, one or more components of the device 200 (e.g., at least one processor 202 and / or at least one memory 204) may be configured to perform those functions. Furthermore, when at least one processor 202 is configured to perform certain functions, those functions may be implemented using, for example, program code 206 included in at least one memory 204.

[0071] The functions described herein can be performed, at least in part, by one or more computer program product components, such as software components. According to an example embodiment, device 200 includes a processor or processor circuitry, such as a microcontroller, configured by program code 206 to perform embodiments of the operations and functions described herein when executed. Program code 206 is provided as an example of instructions that, when executed by at least one processor 202, cause execution of device 200.

[0072] Alternatively or additionally, the functions described herein may be performed at least in part by one or more hardware logic components. For example, but not limited to, illustrative types of hardware logic components that may be used include field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), complex programmable logic devices (CPLDs), graphics processing units (GPUs), and the like.

[0073] Apparatus 200 may be configured to perform or cause the execution of the methods(s) described herein, or may include components for performing the methods(s) described herein. In one example, the components include at least one processor 202 and at least one memory 204 including instructions (e.g., program code 206) configured to cause apparatus 200 to perform the methods(s) when executed by at least one processor 202. Typically, computer program instructions can be executed on an apparatus that provides general-purpose processing capabilities. Such an apparatus may be embedded in, for example, a personal computer, a smartphone, a network device, etc. Thus, the methods(s) may be computer-implemented, for example, based on algorithms(s) executable by general-purpose processing capabilities, an example of which is at least one processor 202. The components may include transmitting or receiving components, such as one or more radio transmitters or receivers, which may be coupled or configured to be coupled to one or more antennas. Apparatus 200 may include, for example, network devices, such as access nodes, access points, base stations, or their central / distributed units. Although device 200 is shown as a single device, it should be understood that, where applicable, the functionality of device 200 can be distributed across multiple devices.

[0074] Figure 3An example of signaling and operations configured for subsequent LTM security procedures is shown. The security procedures can be performed between a UE (such as UE 102) and one or more access nodes (such as access nodes 104, 106, and / or 108) and a CN represented by AMF 308. Each access node may include a centralized unit and one or more distributed units. A first access node may include a centralized unit 302 coupled to a distributed unit 300. A second access node may include a centralized unit 306 coupled to a distributed unit 304. UE 102 may be configured to support multiple radio dual connectivity, and the first access node may be, for example, a source master node (MN1). The second access node may be, for example, a target master node (MN2). The master nodes may be configured to provide control plane connectivity to the core network.

[0075] During the initial access / PDU (Packet Data Unit) session establishment, at operation 310, UE 102 can be registered with the core network (AMF 308) via (multiple) gNBs and a PDU session can be established to provide a data path between UE 102 and the core network.

[0076] At operation 312, a handover preparation procedure can be performed. Handover preparation can be associated with the LTM mobility procedure. Furthermore, the serving CU of UE 102 (e.g., CU 302) can be configured to determine an NCC value. For example, serving CU 302 can be configured to update the NCC value to a specific value, such as NCC=0. CU 302 can then share the updated NCC value with LTM candidate target cells for handover. CU 302 can also notify UE 102 of the configuration of one or more LTM candidate target cells, for example, in an RRC reconfiguration message.

[0077] Furthermore, at operation 312, serving CU 302 can be configured to transmit an NCC value to serving DU 300 for forwarding to UE 102. The NCC value can be transmitted, for example, in a DL transmission message. For instance, the NCC value can be transmitted by CU 302 to DU 300 via a UE context-related message. The UE context-related message can be transmitted via a UE context establishment procedure or a UE context modification procedure performed between CU 302 and DU 300. The NCC value can be included by CU 302, for example, in a UE context establishment request during UE context establishment and / or in a UE context modification request when the established UE context is changed. The F1 Application Protocol (F1AP) can be used to transmit UE context-related messages.

[0078] In one example, service CU 302 can determine whether UE 102 should use the transmitted NCC value in the case of intra-gNB handover. Service CU 302 can be configured to transmit an indication based on this determination regarding whether UE 102 should use the NCC for intra-gNB handover. For example, this indication can be included in a UE context establishment request or UE context modification request sent to the DU. In one example, this indication can be included as an indication flag. For example, when the indication flag is configured to true, UE 102 can be instructed to use vertical key derivation as the selected security key generation process for intra-gNB handover; and when the indication flag is configured to false, UE 102 can be instructed to use horizontal key derivation as the selected security key generation process for intra-gNB handover, and vice versa.

[0079] Alternatively or additionally, the serving CU 302 may determine whether a new key should be used by UE 102 for fault recovery, or whether UE 102 should reuse the latest key in the event of fault recovery. A fault may refer to at least one of a radio link failure or an LTM failure, for example, when UE 102 fails to receive a cell handover command from the serving DU 300. Fault recovery may refer to a handover / cell handover process initiated by UE 102 to a configured target cell. The serving CU 302 may be configured to transmit to the serving DU 300 an indication of whether UE 102 should reuse the latest key or generate a new key for fault recovery. For example, this indication may be included in a UE context establishment request or UE context modification request sent to the DU 300.

[0080] For example, a new information element (IE) can be configured to UE 102 to provide at least one of handover-related indications or fault recovery-related indications within a gNB. One or more indications can be provided to UE 102 via a MAC CE. In one example, one or more indications can be pre-configured by one or more target gNBs, for example, via RRC reconfiguration, during handover preparation at 312.

[0081] At operation 314, UE 102 can be configured to transmit measurement reports to serving DU 300. UE 102 can be configured to measure neighboring cells and can send measurement reports when measurement criteria are detected to be met. The measurement report may include, for example, L1 measurements. Neighboring cells may include configured candidate target cells.

[0082] At operation 316, the serving DU 300 can determine to initiate LTM handover based on the received measurement report. Subsequently, at operation 318, the serving DU 300 can be configured to send a cell handover command to UE 102. The cell handover command can be transmitted via MAC CE. The cell handover command may include the NCC value received from CU 302 at 312. Optionally, the cell handover command may also include at least one of the following indications: whether the NCC will be used by the UE for in-gNB handover and / or whether the latest key or a newly generated key of the serving cell will be used in the event of a fault recovery. The serving DU 300 can be configured to forward one or more indications related to security key generation at the UE based on one or more indications received from CU 302. For example, the indication can be provided by including indication flags in the cell handover command. Alternatively, the DU 300 can be configured to provide the indication by other suitable means, such as including instructions for selecting the security key generation process based on one or more conditions (e.g., in-gNB HO and / or radio link fault recovery). The cell handover command may also include an identifier for the target cell for the inter-gNB handover to be performed by UE 102. In one example, a configuration for at least one indication may be provided in the RRC command configured for the UE. The RRC command may be, for example, an RRC command that includes a configuration of one or more LTM candidate target cells.

[0083] At operation 320, service DU 300 can be configured to send a notification to service CU 302 about a change in the serving cell.

[0084] At operation 322, UE 102 can be configured to determine the key generation process based on the received cell handover command. UE 102 can be configured to determine whether to perform horizontal key derivation or vertical key derivation based on the NCC value received at 318. For example, UE 102 can compare the received NCC value with a previous NCC value obtained by UE 102 before the cell handover. Here, the NCC value obtained by the UE during handover preparation could be NCC=0, and the NCC value received in the cell handover command is also NCC=0. UE 102 compares the two NCC values ​​and detects that the NCC values ​​are the same. Therefore, UE 102 can determine to perform horizontal key derivation.

[0085] In this embodiment, UE 102 may first determine at operation 322 whether the serving cell change is an inter-gNB handover or an intra-gNB handover. If the serving cell change is an inter-gNB handover, the procedure may be performed as described in the previous paragraph. If the serving cell change is an intra-gNB handover, UE 102 may follow the procedure in the previous paragraph or omit the procedure in the previous paragraph based on a received indication specifying whether the NCC should be used for the intra-gNB handover. If the NCC should not be used for the intra-gNB handover, UE 102 may simply continue with the horizontal key derivation. Alternatively, the UE may be configured to, or decide to, reuse an existing key generated for the serving cell earlier. If the NCC should be used for the intra-gNB handover, UE 102 may continue based on the value of the NCC, as described above. A similar procedure may be applied to any serving cell change described herein.

[0086] At operation 324, UE 102 can be configured to send an RRC reconfiguration complete message to a target cell, which may be the distributed element 304 of the second access node. The received RRC reconfiguration complete message can be transmitted by DU 304 to the centralized element 306 of the second access node. DU 304 can also be configured to transmit an access notification to CU 306 at operation 326.

[0087] Subsequently, a path switching procedure can be performed between CU 306 and AMF 308. At operation 328, the centralized unit can be configured to send a path switching request to AMF 308. At operation 330, AMF 308 can be configured to respond to the path switching command with an acknowledgment. This acknowledgment may include a new security configuration. The security configuration may include a new NH value and a new NCC value. For example, the AMF may have incremented the initial NCC value (NCC=0) by 2 and notified the distributed units of the updated value NCC=2.

[0088] At operation 332, CU 306 can be configured to use vertical key generation (K) based on a new security configuration (NH key, NCC). NG-RAN CU 306 can be configured to generate a security key. CU 306 can be configured to notify all other configured CUs (e.g., CU 302) of the new security configuration, including the new NH and the updated NCC. CU 306 can also be configured to perform UE context release at the source gNB (first access node).

[0089] At operation 334, CU 306 (which is now the serving cell after the cell handover) can be configured to indicate the updated NCC value to DU 304, which is now the new serving DU for UE 102. DU 304 can be configured to receive the updated NCC value from CU 306, for example, via an F1AP UE context modification request. DU 304 can also be configured to receive from CU 306 an indication of whether the NCC value will be used for the HO within the gNB. Optionally, DU 304 can be configured to receive from CU 306 an indication of whether UE 102 should use the latest key of the serving cell or generate a new key for the serving cell in the event of a radio link failure recovery. At least one indication can be received, for example, along with the NCC value in an F1AP UE context modification request. One or more indications can be included in the F1AP UE context modification request, for example, in the form of indication flags.

[0090] At operation 338, service DU 304 can be configured to store the NCC received at 334. Service DU 304 can also be configured to store one or more indications received from CU 306. Service DU 304 can be configured to forward the received NCC and one or more indications (if any) to UE 102, for example, by including them in the next cell handover command transmitted to UE 102.

[0091] At operation 340, DU 304 can receive measurement reports from UE 102. The measurement reports may include, for example, L1 measurements of configured candidate target cells.

[0092] At operation 342, DU 304 can perform an LTM handover decision based on the received measurement report. Based on the LTM handover decision, DU 304 can be configured to transmit a MAC CE cell handover command to UE 102, including an updated NCC value (NCC=2). The cell handover command may also include one or more indications if received from CU 306 at operation 334. The cell handover command may include an identifier of the target cell for the cell handover and an indication of the inter-gNB HO to be performed.

[0093] At operation 344, service DU 304 can send a serving cell change notification to service CU 306.

[0094] At operation 346, UE 102 can decide on an LTM cell change. UE 102 can be configured to determine the security key generation process to apply based on the NCC value received from DU 304 at operation 342. UE 102 can compare the NCC value received in the latest cell handover command (NCC=2) with the NCC value received in the previous cell handover command (NCC=0). UE 102 can detect that the NCC value has incremented and therefore determine to perform vertical key derivation. At operation 348, UE 102 can send an RCC reconfiguration complete message to DU 300 of the first access node using the new security configuration. The RCC reconfiguration complete message can be forwarded by DU 300 to CU 302. CU 302 can then decode the message using the new keys(s) received at operation 332.

[0095] Subsequently, a path handover procedure can be performed between the target CU 302 (the new serving cell) and AMF 308. At operation 350, CU 302 can be configured to transmit a path handover request to AMF 308. At operation 352, AMF 308 can respond with a path handover acknowledgment including the updated NCC value and a new NH value generated by AMF 308. For example, AMF 308 can be configured to increment the previous NCC value by 1, up to NCC=3.

[0096] At operation 354, after receiving the new security configuration (new NCC and NH keys) from AMF 308, CU 302 notifies all other configured CUs (e.g., CU 306) of the new security configuration. CU 302 can be configured to perform vertical key generation based on the received NCC value after comparing the updated NCC value (NCC=3) with the previous NCC value (NCC=2). Optionally, CU 302 can perform UE context release at the source cell (second access node). The notification sent by CU 302 may include the generated key.

[0097] At operation 356, CU 302 can be configured to indicate the updated NCC value to DU 300, which is now the new serving DU for UE 102. The updated NCC value can be indicated, for example, via an F1AP UE context modification request message or normally via any DL transmission message. The transmitted message may also include one or more indications determined by CU 302 to be forwarded to UE 102, i.e., whether the UE should use the NCC value for the in-gNB HO and / or, in the event of a radio link failure recovery, whether the UE should use the latest key for the serving cell or generate a new key for the serving cell. In one example, the indication can be provided by using indication flag(s) included in the message. At operation 358, DU 300 can be configured to acknowledge receipt of the message to CU 302, for example, using an F1AP UE context modification response message.

[0098] At operation 360, DU 300 can be configured to store the NCC received at 356. For example, DU 300 can be configured to update the NCC value (NCC=2) stored at DU based on the received NCC value (NCC=3).

[0099] At operation 362, DU 300 can receive measurement reports from UE 102. The measurement reports may include new L1 measurements.

[0100] At operation 364, DU 300 performs an LTM handover decision based on the measurement report and sends a MAC CE cell handover command to UE 102, including the updated NCC value stored at DU 300. Optionally, the cell handover command may include an indication of whether the NCC should be used for in-gNB HO, such as an indication flag. DU 300 may also optionally include an indication of whether the UE should use the latest key of the serving cell or generate a new key for the serving cell for radio link failure recovery. One or more indications transmitted by DU 300 may be based on one or more indications received from CU 302. The cell handover command may also include an identifier of the target cell and an indication to perform in-gNB HO. At operation 366, DU 300 may send a serving cell change notification to serving CU 302.

[0101] At 368, UE 102 can decide to perform an LTM cell change based on the received cell handover command. UE 102 can determine the security key generation process (e.g., vertical / horizontal key derivation) by comparing the NCC received in the cell handover command with a previously stored NCC value. If the cell handover command includes an indication as to whether the received NCC value will be used for the HO within the gNB, UE 102 can further determine the security key generation process based on that indication. At 370, UE 102 can send an RRC reconfiguration complete message to DU 300 using the new security configuration. CU 302 can then decode the message using the new key received at 354.

[0102] Figure 3 The security process shown can notify the UE of the updated NCC value via the MAC layer signaling item of the serving DU. Figure 3 In the MAC CE cell handover command, the NCC value is included. However, to provide robustness against radio link failures, the NCC value can also be configured to be transmitted before the cell handover command, such as... Figure 4 As shown.

[0103] Figure 4 Examples of signaling and operations configured for subsequent LTM and fault recovery security procedures are shown. The security procedures can be performed between a UE (such as UE 102) and one or more access nodes (such as access nodes 104, 106, and / or 108) and a CN represented by AMF 308. Each access node may include a centralized unit and one or more distributed units. A first access node may include a centralized unit 302 coupled to a distributed unit 300. A second access node may include a centralized unit 306 coupled to a distributed unit 304. The first access node may be, for example, a source master node (MN1). The second access node may be, for example, a target master node (MN2).

[0104] Figure 3 and Figure 4 Operations 310 and 312 correspond to each other, so they will not be repeated here.

[0105] At operation 400, serving DU 300 can be configured to transmit to UE 102 a separate message including an NCC value (e.g., NCC=0) received from serving CU 302. The NCC value can be transmitted via MAC layer signaling. The separate message can include, for example, a MAC CE. The separate message can also include one or more indications received from CU 302 to be forwarded to UE 102. The one or more indications can include at least one of the following: an indication to use the NCC value in the case of a HO within the gNB, an indication not to use the NCC value in the case of a HO within the gNB, and an indication not to perform security key generation in the case of a HO within the gNB, an indication to use the latest key of the serving cell in the case of a radio link failure recovery, or an indication to generate a new key for the serving cell in the case of a radio link failure recovery. At least one of the received or transmitted indications can be configured to be provided as an indication flag (false / true) included in the corresponding message. UE 102 can be pre-configured or configured by the network with instructions related to security key generation. UE 102 can be configured to execute according to the instructions based on the received indication flag.

[0106] At operation 314, DU 300 receives an L1 measurement report from UE 102. At operation 316, based on the L1 measurement report, DU 300 can perform a decision regarding the LTM HO. After the LTM HO decision, DU 300 can be configured to transmit a cell handover command to UE 102. The cell handover command may include, for example, an identifier of the target cell and / or an indication of an inter-NB HO to be performed by UE 102. Because the NCC value was previously sent to UE 102 in a separate MAC CE message, the cell handover command may not need to include the NCC value. At operation 320, DU 300 can transmit a notification regarding the cell change to serving CU 302.

[0107] At operation 404, UE 102 can determine the LTM cell change based on the received cell handover command. UE 102 can be configured to determine the security key generation to be applied based on the NCC value received at operation 400. UE 102 can compare the received NCC value with a previous NCC value obtained by UE 102 and detect that the NCC values ​​are the same. Because the NCC value has not changed, UE 102 can determine to perform horizontal key derivation. When the MAC CE message also includes one or more indications, UE 102 can be configured to further determine the security key generation process based on the received indications(s).

[0108] Then, the handover and security process can continue as follows: Figure 3Operations 324, 326, 328, 330, 332 and 334 have already been described, so their descriptions will not be repeated here.

[0109] After the new service DU 304 has received the updated NCC value from CU 306 at operation 334, DU 304 can be configured to transmit the updated NCC value to UE 102 in a separate message before the next cell handover command. At operation 406, DU 304 can be configured to transmit the updated NCC value to UE 102 via MAC layer signaling (such as in a MAC CE message). For example, DU 304 can be configured to transmit the NCC value to UE 102 as soon as it is received from CU 306. As described in operation 400, if DU 304 also receives at least one indication to be forwarded to UE 102 from CU 306, this indication can be included in the MAC CE message. After transmitting the MAC CE message to UE 102, DU 304 can be configured to transmit a UE context modification response message to CU 306. However, this is just an example; MAC CE messages can also be configured to be transmitted after the UE context modification response, as long as the MAC CE message is transmitted before the next cell handover command.

[0110] At operation 408, UE 102 can be configured to store the NCC value and any indications received at 406 for further use.

[0111] At operation 340, UE 102 can transmit an L1 measurement report to DU 304. DU 304 can then perform an LTM HO decision based on the L1 measurement report. However, a radio link failure may occur at operation 410 before DU 304 transmits the cell handover command to UE 102 at operation 412. In this case, a radio link failure may occur, preventing UE 102 from receiving the cell handover command.

[0112] UE 102 can be configured to detect radio link failure events and initiate LTM recovery at operation 414. At operation 414, UE 102 can be configured to determine to perform LTM recovery on the configured LTM candidate target cell. UE 102 can be configured to select an LTM candidate target cell and determine the security key generation process based on the NCC value already received in the MAC CE message at 406. UE 102 can be configured to compare the NCC value (NCC=3) in the MAC CE message with a previously used NCC value (NCC=2) for key derivation and detect that the received and previously used NCC values ​​are different from each other. Therefore, based on this comparison, UE 102 can determine to perform vertical key derivation by using the received NCC value. If UE 102 receives at least one indication in the MAC CE message, UE 102 can be configured to consider the indication when determining the security key generation process to be applied. For example, if the selected LTM candidate target cell for recovery is a serving / source LTM cell, UE 102 can be configured to use the old key or as instructed by the network (e.g., based on received instructions for fault recovery). If the selected LTM candidate is a target cell, UE 102 can use a previously generated key (if any) for that target cell during LTM execution on that target cell. If the selected LTM candidate cell is any other cell, UE 102 should consider whether the received NCC was previously used and that instruction to perform new key generation.

[0113] Then, at operation 414, UE 102 can transmit RRC reconfiguration messages to the DU of the selected LTM candidate target cell for recovery.

[0114] After this, the path switching process can be performed, and new security configurations can be shared, such as those already in use. Figure 3 The corresponding operations 350, 352, 354 and 356 are described in the table, so they will not be repeated here.

[0115] After the NCC value updated by AMF 308 at operation 352 is received by DU 300 at operation 356 via CU 302, DU 300 can be configured to forward the updated NCC value (NCC=3) to UE 102 in a separate MAC CE message, which is configured to be transmitted before the next cell handover command. After the MAC CE message is transmitted from DU 300 to UE 102 at operation 418, DU 300 can be configured to respond to CU 302 with a UE context response message at operation 358. The updated NCC received by UE 102 can be stored at UE 102 for subsequent (multiple) LTM handovers.

[0116] Figure 5 An example of a method 500 for a security process is shown. Method 500 may be performed by a mobile device such as a UE (e.g., UE 102) or by a means configured to control the functions of the UE when installed in the UE.

[0117] At operation 502, the method may include: receiving a next-hop chain counter value from the distributed unit of the access node of the serving cell of the user equipment for a subsequent layer 1 / layer 2 triggered mobility procedure via media access control layer signaling.

[0118] At operation 504, the method may include: determining a security key generation process to be applied to a subsequent layer 1 / layer 2 triggered mobility process based on the received next-hop chain counter value.

[0119] Figure 6 An example of a method 600 for a security procedure used in a subsequent LTM process is shown. Method 600 can be performed by a network device, such as an access node (e.g., gNB 104, 106, and / or gNB 108) or a portion thereof, such as a distributed unit of the access node (e.g., DU 300 and / or DU 304). In one example, method 600 can be performed by a means configured to control the functionality of the distributed unit when installed in it.

[0120] At 602, the method may include: receiving a message including a next-hop chain counter value from the centralized unit of the access node.

[0121] At 604, the method may include: updating the next-hop chain counter value stored in the distributed cell associated with the serving cell of the user equipment at the access node based on the received next-hop chain counter value.

[0122] At 606, the method may include transmitting an updated next-hop chain counter value to the user equipment via media access control layer signaling for a mobility procedure triggered by a subsequent layer 1 / layer 2.

[0123] In one example, the method for the security procedures used in the subsequent LTM process can be performed by a centralized unit of the access node (e.g., CU302 and / or CU 306) or by means configured to control the functions of the centralized unit when installed in the centralized unit.

[0124] The method may include: determining that a next-hop chain counter value stored at a centralized unit of the access node has been updated; and transmitting a message including the determined next-hop chain counter value to a distributed unit of the access node associated with the serving cell of the user equipment, the message being forwarded by the distributed unit to the user equipment for subsequent Layer 1 / Layer 2 triggered mobility procedures. The determined next-hop chain counter value may include a value updated by the centralized unit of the access node during the handover preparation process or an updated value received from the core network (e.g., AMF) during the path handover process.

[0125] The method may further include: determining whether the next-hop link counter value will be used by the user equipment for intra-access node handover; and based on the determination, transmitting an indication to the distributed unit whether the next-hop link counter value will be used by the user equipment for intra-access node handover.

[0126] The method may further include: in the event of a radio link failure recovery, determining that the user equipment will use one of the following: the latest security key of the serving cell, or a new security key generated by the user equipment for the serving cell; and based on the determination, transmitting to the distributed unit an instruction for the equipment to use one of the following in the event of a radio link failure recovery: the latest security key of the serving cell, or a new security key generated for the serving cell.

[0127] The method may further include transmitting at least one of the following in at least one of the User Equipment Context Establishment Request Message or User Equipment Context Modification Request Message: a next-hop chain counter value, an indication of whether to use the next-hop chain counter for handover within the access node, or the use of a latest key or a newly generated key.

[0128] Further features of these methods are derived directly, for example, from the functionality of UE 102, access nodes(s) 104, 106 and / or 108, distributed units(s) 300 and / or 304, or centralized units(s) 302 and / or 306 as described throughout the specification, claims, and drawings, and therefore will not be repeated here. Apparatus (e.g., a mobile device or access node such as UE 102) may be configured to perform or cause the performance of any aspect of the methods(s) described herein. Furthermore, a computer program, computer program product, or (non-transitory) computer-readable medium may include instructions that, when executed by the apparatus, cause the apparatus to perform any aspect of the methods(s) described herein. Additionally, the apparatus may include components for performing any aspect of the methods(s) described herein. According to an example embodiment, the components include at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus to perform at least any aspect of the methods(s).

[0129] The ranges or device values ​​given herein may be extended or modified without losing the desired effect. Furthermore, any embodiment may be combined with another embodiment unless expressly permitted.

[0130] Although the subject matter has been described in language specific to structural features and / or actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as examples of implementing the claims, and other equivalent features and actions are intended to fall within the scope of the claims.

[0131] It should be understood that the above benefits and advantages may relate to one embodiment or several embodiments. The embodiments are not limited to embodiments that solve any or all of these problems or have any or all of these benefits and advantages. It will also be understood that references to "projects" may refer to one or more of those projects.

[0132] The steps or operations of the methods described herein can be performed in any suitable order, or simultaneously where appropriate. Furthermore, individual boxes can be removed from any method without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above can be combined with aspects of any other example embodiments described to form further example embodiments without losing the desired effect.

[0133] The term “comprising” is used herein to mean including the identified method, frame, or element, but such frame or element does not include an exclusive list, and the method or apparatus may include additional frames or elements.

[0134] As used herein, “at least one of the following: ” and “at least one of ” and similar wording (where the list of two or more elements is connected by “and” or “or”) means at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0135] Although a topic may be referred to as the "first" or "second" topic, this does not necessarily indicate any order or importance of the topics. Rather, such a property can be used simply to distinguish between topics.

[0136] As used herein, the term "circuit" may refer to one or more of the following: (a) a hardware circuit implementation only (such as an implementation only in analog and / or digital circuitry), and (b) a combination of hardware circuitry and software, such as (if applicable): (i) a combination of (multiple) analog and / or digital hardware circuitry with software / firmware, and (ii) (multiple) hardware processors with any portion of software (including (multiple) digital signal processors, software, and (multiple) memories, which work together to enable a device such as a mobile phone or server to perform various functions), and (c) (multiple) hardware circuitry and / or (multiple) processors, such as (multiple) microprocessors or portions thereof, that require software (e.g., firmware) for operation, but the software may be absent when operation is not required. This definition of circuitry applies to all uses of the term herein (including in any claim).

[0137] As another example, as used in this application, the term "circuit" also encompasses only hardware circuitry or a processor (or multiple processors) or a portion thereof and its accompanying software and / or firmware. The term "circuit" also encompasses, for example and if applicable to a particular claim element, baseband integrated circuits or processor integrated circuits for mobile devices or similar integrated circuits in servers, cellular network devices, or other computing or network devices.

[0138] It should be understood that the above description is given by way of example only, and various modifications can be made by those skilled in the art. The above specification, examples, and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a degree of specificity or by reference to one or more individual embodiments, many changes can be made to the disclosed embodiments by those skilled in the art without departing from the scope of this specification.

Claims

1. An apparatus for a user equipment, comprising: At least one processor; as well as At least one memory, comprising instructions that, when executed by the at least one processor, cause the device to: The next-hop chain counter value for subsequent layer 1 / layer 2 triggered mobility procedures is received from the distributed unit of the access node of the serving cell of the user equipment via media access control layer signaling. as well as Based on the received next-hop chain counter value, a security key generation process is determined to be applied to the subsequent layer 1 / layer 2 triggered mobility process.

2. The apparatus of claim 1, wherein the next hop chain counter value is received in at least one of a cell handover command or a separate message received from the distributed unit prior to the cell handover command.

3. The apparatus according to any one of claims 1 or 2, further comprising: The system receives, via media access control layer signaling, an indication from the distributed unit of the access node regarding whether the received next-hop link counter value will be used by the user equipment for handover within the access node; and Based on the received instructions, the security key generation process for handover within the next access node is determined.

4. The apparatus of claims 2 and 3, wherein at least one of the cell handover command or the individual message further includes an indication of whether to use the received next-hop chain counter value for intra-access node handover.

5. The apparatus according to any one of claims 1 to 4, further comprising: In the event of a radio link failure recovery, an instruction to use one of the following is received from the distributed unit of the access node via media access control layer signaling: the latest security key of the serving cell, or a new security key generated for the serving cell; and The security key generation process is determined based on the received instructions for radio link failure recovery.

6. The apparatus of claim 5 and at least one of claim 2 or claim 4, wherein at least one of the cell handover command or the individual message further includes an indication to use either the latest security key of the serving cell or a new security key generated for the serving cell in the event of a radio link failure recovery.

7. The apparatus according to any one of claims 1 to 6, wherein the media access control signaling includes a media access control (MAC) control element.

8. The apparatus according to any one of claims 1 to 7, further comprising: Detecting radio link faults; Candidate cells for fault recovery are selected based on the detected radio link faults. A subsequent mobility procedure is initiated to the selected candidate cell for fault recovery, wherein the security key for the mobility procedure is updated based on the determined security key generation procedure.

9. An apparatus for a distributed unit, comprising: At least one processor; as well as At least one memory storing instructions that, when executed by the at least one processor, cause the device to at least: Receive a message including the next-hop chain counter value from the centralized unit of the access node; Based on the received next-hop chain counter value, update the next-hop chain counter value stored in the distributed unit associated with the serving cell of the user equipment in the access node; as well as The updated next-hop chain counter value is transmitted to the user equipment via media access control layer signaling for subsequent layer 1 / layer 2 mobility procedures.

10. The apparatus of claim 9, wherein the message comprises at least one of the following: User device context creation request or user device context modification request.

11. The apparatus according to any one of claims 9 to 10, further comprising: The centralized unit of the access node receives an indication of whether the received next-hop chain counter value will be used by the user equipment for handover within the access node; and The instruction is transmitted to the user equipment via media access control layer signaling.

12. The apparatus according to any one of claims 9 to 11, further comprising: The user equipment receives an instruction from the centralized unit of the access node to use one of the following for radio link failure recovery: the latest security key of the serving cell, or the generation of a new security key for the serving cell; and The received instruction is transmitted to the user equipment via media access control signaling.

13. The apparatus according to any one of claims 9 to 12, wherein the media access control layer signaling includes a media access control (MAC) element.

14. The apparatus of claim 13, wherein the media access control layer signaling comprises at least one of the following: - Cell handover command; or - A separate message preceding the cell handover command transmitted by the distributed unit.

15. A method comprising: The next-hop chain counter value for subsequent layer 1 / layer 2 triggered mobility procedures is received from the distributed unit of the access node of the serving cell of the user equipment via media access control layer signaling. as well as Based on the received next-hop chain counter value, a security key generation process is determined to be applied to the subsequent layer 1 / layer 2 triggered mobility process.

16. A method comprising: Receive a message including the next-hop chain counter value from the centralized unit of the access node; Based on the received next-hop chain counter value, update the next-hop chain counter value stored in the distributed unit associated with the serving cell of the user equipment in the access node; as well as The updated next-hop chain counter value is transmitted to the user equipment via media access control layer signaling for subsequent layer 1 / layer 2 mobility procedures.

Images