Facilitating user equipment security updates in conjunction with mobility operations

Abstract

Embodiments include methods for a user equipment (UE). Such methods include receiving from a first radio access network (RAN) node a mobility configuration including one or more mobility candidate configurations for a mobility operation to one or more mobility candidate cells provided by a second RAN node. Such methods include receiving from the first RAN node a command to execute the mobility operation to a first one of the mobility candidate cells, and executing the mobility operation to the first mobility candidate cell. Such methods include performing one or more of the following in conjunction with or after the mobility operation: a first security update based on a first set of security information related to the second RAN node, obtained before executing the mobility operation; and a second security update based on a second set of security information related to the second RAN node, obtained after executing the mobility operation.

Description

[0001] FACILITATING USER EQUIPMENT SECURITY UPDATES IN CONJUNCTION WITH MOBILITY OPERATIONS TECHNICAL FIELD

[0002] The present disclosure relates generally to wireless networks, and more specifically to techniques for providing information needed for user equipment (UE) security updates during mobility operations between cells, such as between cells served by different radio access network (RAN) nodes.

[0003] BACKGROUND

[0004] The fifth generation (5G) of cellular systems has been standardized within the Third-Generation Partnership Project (3GPP). 5G was developed for maximum flexibility to support various use cases including enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device-to-device (D2D), and several others. 5G was initially specified in 3GPP Release 15 (Rel-15) and continues to evolve through subsequent releases.

[0005] Figure 1 illustrates a high-level view of an exemplary 5G network architecture, consisting of a Next Generation Radio Access Network (NG-RAN, 199) and a 5G Core (5GC, 198). The NG-RAN can include one or more gNodeB’s (gNBs) connected to the 5GC via one or more NG interfaces, such as gNBs (100, 150) connected via respective interfaces (102, 152). More specifically, the gNBs can be connected to one or more Access and Mobility Management Functions (AMFs) in the 5GC via respective NG-C interfaces and to one or more User Plane Functions (UPFs) in 5GC via respective NG-U interfaces. The 5GC can include various other network functions (NFs), such as Session Management Function(s) (SMF).

[0006] In addition, the gNBs can be connected to each other via one or more Xn interfaces, such as Xn interface (140) between gNBs (100, 150). The radio technology for the NG-RAN is often referred to as “New Radio” (NR). With respect to the NR interface to UEs, each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of the gNBs can serve a geographic coverage area including one or more cells and, in some cases, can also use various directional beams to provide coverage in the respective cells. In general, a DL “beam” is a coverage area of a network-transmitted reference signal (RS) that may be measured or monitored by a UE.

[0007] NG RAN logical nodes (e.g., gNB 100) include a Central Unit (CU or gNB-CU, e.g., 110) and one or more Distributed Units (DU or gNB-DU, e.g., 120, 130). CUs are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. DUs are decentralized logical nodes that host lower layer protocols and can include,depending on the functional split option, various subsets of the gNB functions. Each CU and DU can include various circuitry needed to perform their respective functions, including processing circuitry, communication interface circuitry (e.g., transceivers), and power supply circuitry.

[0008] A gNB-CU connects to one or more gNB-DUs over respective Fl logical interfaces (e.g., 122 and 132 shown in Figure 1). However, each gNB-DU can be connected to only one gNB-CU. The gNB-CU and its connected gNB-DU(s) are only visible to other gNBs and the 5GC as a gNB. In other words, the Fl interface is not visible beyond gNB-CU.

[0009] Access stratum (AS) security in the 5G network includes integrity protection and ciphering of radio resource control (RRC) signaling radio bearers (SRBs) and user data radio bearers (DRBs). Each gNB applies four different AS security keys: one for integrity protection of RRC signaling (KRRCint), one for ciphering of RRC signaling (KRRCenc), one for integrity protection of user data (Kupint) and one for ciphering of user data (Kupenc).

[0010] As described in 3GPP TS 38.501 (vl 8.4.0), whenever an initial AS security context needs to be established between a UE and a gNB, both the AMF and the UE derive the K§NB key of the gNB and a Next Hop parameter (NH), based on the KAMF key provided by the AMF. The UE and the gNB use K§NB to secure the communication between each other, including derivation of the four AS security keys mentioned above. A NH Chaining Counter (NCC) is associated with each KgNB and NH parameter, and each K§NB is associated with the NCC corresponding to the NH value from which the K§NB was derived.

[0011] Seamless mobility is a key feature of 3GPP radio access technologies (RATs). In general, a RAN (e.g., NG-RAN) configures a UE to perform and report radio resource management (RRM) measurements to assist network-controlled mobility decisions, such as for handover from a serving cell to a neighbor cell. Seamless handovers ensure that the UE moves around in the coverage area of different cells without excessive interruption to data transmission.

[0012] Conventionally, serving cell change is triggered by layer 3 (L3, e.g., RRC) measurements and involves RRC signaling to change PCell and PSCell (e.g., when DC is configured) and to release / add SCells. L3 serving cell change - also referred to as handover (HO) - also involves layer 1 (LI) and layer 2 (L2) resets, leading to longer latency, increased signaling overhead, and longer interruptions than for intra-cell beam switching.

[0013] Certain L3 mobility operations may also involve changes to integrity protection and ciphering algorithms as well the AS keys KgNB, KRRCint, KRRCenc, Kupint and Kupenc. For example, during handovers, the basis for K§NB to be used between the UE and the target RAN node (e.g., gNB) - called KNG-RAN* - is derived from either the currently active K§NB or from the NH parameter. Deriving KNG-RAN* from the currently active K§NB is referred to as a “horizontal key derivation” requires only the currently active K§NB and other local information such as physicalcell identity (PCI) and downlink (DL) frequency. To facilitate horizontal key derivation, the UE receives an indication of the NH value currently being used by the source RAN node (e.g., gNB). This indication is an eight-bit next-hop chaining count (NCC) value that points to a specific NH value that the UE and AMF use as a base key. Conventionally, when it is sent to the UE, the NCC value is secured by the source RAN node using one or more of the existing AS keys.

[0014] In contrast, deriving KNG-RAN* from the NH parameter is referred to as “vertical key derivation” and can only be done based on master key material available at the UE and the AMF. For vertical key derivation, the target RAN node (e.g., gNB) will receive a derived key (based on the next NH value) and an NCC value that the UE needs in order to understand which NH value to use for the vertical key derivation. As mentioned above, the NCC value is conventionally secured when it is provided to the UE. In general, vertical key derivation is more complex than horizontal key derivation.

[0015] 3GPP Rel-18 includes new mobility procedures that facilitate serving cell changes via L1 / L2 signaling to address these problems and / or difficulties. These new procedures are often referred to as L1 / L2 based inter-cell mobility or L1 / L2 triggered mobility (LTM). In LTM, a UE is pre-configured by its serving RAN node with one RRC configuration per LTM candidate cell, sometimes referred to as an “LTM candidate cell configuration.” The UE performs lower-layer measurements on its configured LTM candidate cells and transmits corresponding measurement reports to the RAN node, based on which the RAN node triggers execution of a LTM cell switch procedure by the UE to one of the configured LTM candidate cells. The RAN node may trigger the LTM cell switch procedure by sending the UE an LTM cell switch command, which is a lower-layer message (e.g., MAC CE).

[0016] The Rel-18 mobility enhancements also support the split CU / DU architecture of Figure 1, including intra-DU and inter-DU / intra-CU LTM cell switches. In the inter-DU / intra-CU scenario, the candidate cell is served by a neighbor DU to the (serving or source) DU that currently provides the UE’s PCell. In the intra-DU scenario, the candidate cell is served by the same DU that currently provides the UE’s PCell (or PSCell, for SCG change in DC). In terms of security, the NCC value does not need to change for Rel-18 intra-CU LTM since the UE will communicate with the same CU using the same keys before and after an LTM cell switch.

[0017] SUMMARY

[0018] 3GPP Rel-19 will support inter-CU LTM between source and candidate cells associated with different CUs. In this inter-CU LTM scenario, it may be necessary and / or desirable to use vertical key derivation., which requires the relevant NCC value to be sent to the UE in conjunction with the LTM procedure. For L3 mobility, this was done using secure RRC signaling (e.g., in aHO command). However, LTM uses lower-layer signaling (e.g., LTM cell switch MAC CE) that is neither encrypted nor integrity-protected. Even if non-secure transport of NCC is acceptable, it is unclear where this eight-bit value can be added to an existing LTM cell switch MAC CE. Furthermore, even if added, this addition may cause a UE to misinterpret other existing fields in the LTM cell switch MAC CE. Solutions to these problems, issues, and / or difficulties are needed.

[0019] An object of embodiments of the present disclosure is to provide information (e.g., NCC value) needed for key derivation in conjunction with LTM or other mobility operations, such as by enabling and / or facilitating solutions to exemplary problems summarized above and described in more detail below.

[0020] Embodiments include methods (e.g., procedures) for a UE configured for mobility between cells of a radio access network (RAN, e.g., E-UTRAN, NG-RAN).

[0021] These exemplary methods include receiving, from a first RAN node via a serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node. These exemplary methods also include receiving from the first RAN node a first message including a command to execute the mobility operation to a first one of the mobility candidate cells. These exemplary methods also include executing the mobility operation from the serving cell to the first mobility candidate cell. These exemplary methods also include performing one or more of the following in conjunction with or after the mobility operation:

[0022] • a first security update based on a first set of security information related to the second RAN node, obtained before executing the mobility operation; and

[0023] • a second security update based on a second set of security information related to the second RAN node, obtained after executing the mobility operation.

[0024] In some embodiments, these exemplary methods also include, after executing the mobility operation, receiving from the second RAN node a second message including a command to perform the second security update. The second message includes the second set of security information.

[0025] In some of these embodiments, the second message is unprotected by either encryption or integrity protection when it is received from the second RAN node. In some variants of these embodiments, these exemplary methods also include initiating a message timer after executing the mobility operation. In some further variants, the second security update is performed based on the second set of security information when the unprotected second message is received while the message timer is running. Also, when the unprotected second message is received after the message timer has expired, these exemplary methods also include refraining from performing the second security update and enters a non-connected state with respect to the second RAN node.In some further variants, these exemplary methods also include performing one or more the following operations while the message timer is running and the unprotected second message has not been received:

[0026] • discarding a further message that includes at least part of the second set of security information, wherein the further message is protected by encryption and / or integrity protection; and

[0027] • refraining from performing any security updates with respect to the second RAN node.

[0028] In some embodiments, the received mobility configuration is secured based on a first security key associated with the first RAN node, and the first security key is associated with the following: a first key identifier, and a first parameter from which a second security key may be derived. In some of these embodiments, the first key identifier is a next hop chaining count (NCC) and the first parameter is a next hop (NH) parameter.

[0029] In some embodiments, content of the first message is neither encrypted nor integrity-protected when it is received from the first RAN node.

[0030] In some of these embodiments, performing the first security update based on the first set of security information include deriving a second security key usable to secure communication with the second RAN node. In some of these embodiments, performing the second security update based on the second set of security information deriving a third security key usable to secure communication with the second RAN node. In some variants of these embodiments, at least one of the second security key and the third security key is derived based on one or more of the following associated with the first mobility candidate cell: a physical cell identity (PCI), and a downlink (DL) carrier frequency.

[0031] Other embodiments include exemplary methods (e.g., procedures) for a first RAN node configured to provide a serving cell for a UE. In general, these exemplary methods may be complementary to the exemplary methods for a UE summarized above.

[0032] These exemplary methods include sending, to a UE via the serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node. These exemplary methods include sending to the UE a first message including a command to execute the mobility operation to a first one of the mobility candidate cells. The mobility configuration and / or the first message includes a first set of security information related to the second RAN node, which configures the UE to perform a first security update in conjunction with the mobility operation.

[0033] In some embodiments, these exemplary methods also include receiving the one or more mobility candidate configurations from the second RAN node, i.e., prior to sending them to theUE. In some embodiments, these exemplary methods also include, after sending the first message, sending to the second RAN node a notification of the mobility operation by the UE.

[0034] Other embodiments include exemplary methods (e.g., procedures) for a second RAN node configured to provide one or more mobility candidate cells for a UE. In general, these exemplary methods may be complementary to the exemplary methods for a UE and a first RAN node, summarized above.

[0035] These exemplary methods include determining that the UE has executed a mobility operation from a serving cell provided by a first RAN node to a first one of the mobility candidate cells provided by the second RAN node. These exemplary methods also include subsequently sending to the UE a second message including a command to perform a second security update based on a second set of security information also included in the second message.

[0036] In some embodiments, determining that the UE has executed the mobility operation in is based on receiving one or more of the following: a notification from the first RAN node, a notification from a distributed unit (DU) of the second RAN node, or a message from the UE via the first mobility candidate cell.

[0037] In some embodiments, these exemplary methods also include sending, to the first RAN node, one or more mobility candidate configurations for the mobility operation to the respective one or mobility candidate cells. The mobility operation is based on a first one of the mobility candidate configurations associated with the first mobility candidate cell.

[0038] The following features may be common to various UE and RAN node embodiments summarized above.

[0039] In some embodiments, the first and second RAN nodes may be different CUs or different gNBs, such that the mobility operation is inter-CU or inter-gNB. In some embodiments, the first message is one of the following: a MAC CE, downlink control information (DCI), or an RRC message. In some embodiments, the second message is one of the following: a MAC CE, DCI, or an RRC message.

[0040] In some embodiments, the mobility operation is an LTM cell switch. In other embodiments, the mobility operation is an L3 handover.

[0041] In some embodiments, the first set of security information is included in one or more of the following: the mobility configuration, and the first message. In some embodiments, the first set of security information includes or indicates one or more of the following:

[0042] • a first security key associated with the first RAN node;

[0043] • a first key identifier associated with the first security key;

[0044] • a first parameter associated with the first security key;• identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0045] • an indication to perform a security update in conjunction with the mobility operation; • to perform a vertical key derivation in conjunction with the mobility operation;

[0046] • to perform a horizontal key derivation in conjunction with the mobility operation;

[0047] • to perform a further security update for the second RAN node after the mobility operation;

[0048] • one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed; and

[0049] • one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0050] In some embodiments, the second set of security information includes or indicates one or more of the following:

[0051] • a second security key associated with the second RAN node;

[0052] • a second key identifier associated with the second security key;

[0053] • a second parameter from which a third security key may be derived;

[0054] • identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0055] • to perform a security update;

[0056] • to perform a vertical key derivation;

[0057] • to perform a horizontal key derivation;

[0058] • one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0059] In some embodiments, the first and second RAN nodes different gNBs, such that the mobility operation is inter-gNB. In other embodiments, the first and second RAN nodes are different CUs, such that the mobility operation is inter-CU.

[0060] Other embodiments, variants, and features of the exemplary methods summarized above are described herein. Other embodiments include UEs (e.g., wireless devices) and RAN nodes (e.g., base stations, eNBs, gNBs, ng-eNBs, etc.) configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include non-transitory, computer-readable media storing program instructions that, when executed by processing circuitry, configure such UEs and RAN nodes to perform operations corresponding to any of the exemplary methods described herein.

[0061] These and other embodiments described herein may provide various advantages, benefits, and / or solutions to problems. For example, by providing integrity protection for lower layersignaling, embodiments may facilitate UE security key update for LTM without higher layer (e.g., RRC) signaling, which supports LTM advantages such as reduced latency, signaling, and / or interruptions. As such, embodiments may facilitate necessary updates for encryption and integrity protection as the UE moves between and within cells in the RAN, thereby increasing security of signaling and user data carried by radio bearers secured in this manner.

[0062] These and other objects, features, and advantages of embodiments of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below.

[0063] BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 shows a high-level view of an exemplary 5G / NR network architecture.

[0065] Figure 2 shows a logical architecture for an NG-RAN node arranged in a split CU / DU architecture.

[0066] Figure 3 shows exemplary NR user plane (UP) and control plane (CP) protocol stacks. Figure 4 illustrates security key derivation for handover and other UE mobility procedures. Figure 5 shows a signaling diagram for an exemplary two-stage L3 handover for a UE. Figure 6 shows an exemplary LTM cell switch MAC CE.

[0067] Figures 7-11 show some example MAC CEs that may be utilized in various embodiments of the present disclosure.

[0068] Figure 12 shows a flow diagram of an exemplary method for a UE (e.g., wireless device), according to various embodiments of the present disclosure.

[0069] Figure 13 shows a flow diagram of an exemplary method for a first RAN node (e.g., base station, eNB, gNB, DU, etc.), according to various embodiments of the present disclosure.

[0070] Figure 14 shows a flow diagram of an exemplary method for a second RAN node (e.g., base station, eNB, gNB, DU, etc.), according to various embodiments of the present disclosure.

[0071] Figures 15-16 show two example communication systems according to some embodiments of the present disclosure.

[0072] Figure 17 shows an example wireless device according to some embodiments of the present disclosure.

[0073] Figure 18 shows an example network node according to some embodiments of the present disclosure.

[0074] Figure 19 shows an example virtualization environment in which some embodiments of the present disclosure may be virtualizedDETAILED DESCRIPTION

[0075] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art.

[0076] In general, all terms used herein are to be interpreted according to their ordinary meaning to a person of ordinary skill in the relevant technical field, unless a different meaning is expressly defined and / or implied from the context of use. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise or clearly implied from the context of use. The operations of any methods and / or procedures disclosed herein do not have to be performed in the exact order disclosed, unless an operation is explicitly described as following or preceding another operation and / or where it is implicit that an operation must follow or precede another operation. Any feature of any embodiment disclosed herein can apply to any other disclosed embodiment, as appropriate. Likewise, any advantage of any embodiment described herein can apply to any other disclosed embodiment, as appropriate.

[0077] Furthermore, the following terms are used throughout the description given below:

[0078] • Radio Access Node: As used herein, a “radio access node” (or equivalently “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) that operates to wirelessly transmit and / or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., gNB in a 3GPP 5G / NR network or an enhanced or eNB in a 3GPP LTE network), base station distributed components (e.g., CU and DU), a high-power or macro base station, a low-power base station (e.g., micro, pi co, femto, or home base station, or the like), an integrated access backhaul (IAB) node, a transmission point (TP), a transmission reception point (TRP), a remote radio unit (RRU or RRH), and a relay node.

[0079] • Core Network Node: As used herein, a “core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a serving gateway (SGW), aPDN Gateway (P-GW), a Policy and Charging Rules Function (PCRF), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), a Charging Function (CHF), a Policy Control Function (PCF), an Authentication Server Function (AUSF), a location management function (LMF), or the like.• Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device that is capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other wireless devices. Communicating wirelessly can involve transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information through air. Unless otherwise noted, the term “wireless device” is used interchangeably herein with the term “user equipment” (or “UE” for short), with both of these terms having a different meaning than the term “network node”.

[0080] • Radio Node: As used herein, a “radio node” can be either a “radio access node” (or equivalent term) or a “wireless device.”

[0081] • Network Node: As used herein, a “network node” is any node that is either part of the radio access network (e.g., a radio access node or equivalent term) or of the core network (e.g., a core network node discussed above) of a cellular communications network. Functionally, a network node is equipment capable, configured, arranged, and / or operable to communicate directly or indirectly with a wireless device and / or with other network nodes or equipment in the cellular communications network, to enable and / or provide wireless access to the wireless device, and / or to perform other functions (e.g., administration) in the cellular communications network.

[0082] • Node: As used herein, the term “node” (without prefix) can be any type of node that can in or with a wireless network (including RAN and / or core network), including a radio access node (or equivalent term), core network node, or wireless device. However, the term “node” may be limited to a particular type (e.g., radio access node, IAB node) based on its specific characteristics in any given context.

[0083] The above definitions are not meant to be exclusive. In other words, various ones of the above terms may be explained and / or described elsewhere in the present disclosure using the same or similar terminology. Nevertheless, to the extent that such other explanations and / or descriptions conflict with the above definitions, the above definitions should control.

[0084] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system and can be applied to any communication system that may benefit from them.

[0085] Figure 2 shows a logical architecture for an NG-RAN node (e.g., gNB or ng-eNB) arranged in the split CU / DU architecture, such as gNB 100 in Figure 1. This logical architecture separates the CU into control plane (CP) and user plane (UP) functionality, called CU-C (or CU-CP) and CU-U (or CU-UP) respectively. Furthermore, each of the NG, Xn, and Fl interfaces is split intoa CP interface (e.g., NG-C) and a UP interface (e.g., NG-U). Moreover, the CU-U and CU-C can communicate via an El interface. Each DU may be connected to only one CU-C, and each CU-U may be connected to only one CU-C. However, a single DU may be connected to multiple CU-Us under the control of the same CU-C, or a single CU-U may be connected to multiple DUs under the control of the same CU-C. Note that the terms “Central Entity” and “Distributed Entity” in Figure 2 refer to physical network nodes.

[0086] Figure 3 shows an exemplary configuration of NR UP and CP protocol stacks between a UE (310), a gNB (320), and an AMF (330). Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP) layers between UE and gNB are common to UP and CP. PDCP provides ciphering / deciphering, integrity protection, sequence numbering, reordering, and duplicate detection for both CP and UP, as well as header compression and retransmission for UP data.

[0087] On the UP side, Internet protocol (IP) packets arrive to PDCP as service data units (SDUs), and PDCP creates protocol data units (PDUs) to deliver to RLC. The Service Data Adaptation Protocol (SDAP) layer handles quality-of-service (QoS) including mapping between QoS flows and Data Radio Bearers (DRBs) and marking QoS flow identifiers (QFI) in UL and DL packets. RLC transfers PDCP PDUs to MAC through logical channels (LCH). RLC provides error detection / correction, concatenation, segmentation / reassembly, sequence numbering, reordering of data transferred to / from the upper layers. MAC provides mapping between LCHs and PHY transport channels, LCH prioritization, multiplexing into or demultiplexing from transport blocks (TBs), hybrid ARQ (HARQ) error correction, and dynamic scheduling (in gNB). PHY provides transport channel services to MAC and handles transfer over the NR radio interface, e.g., via modulation, coding, antenna mapping, and beam forming.

[0088] On the CP side, the non-access stratum (NAS) layer between UE and AMF handles UE / gNB authentication, mobility management, and security control. RRC sits below NAS in the UE but terminates in the gNB rather than the AMF. RRC controls communications between UE and gNB at the radio interface as well as the mobility of a UE between cells in the NG-RAN. RRC also broadcasts system information (SI) and performs establishment, configuration, maintenance, and release of DRBs and Signaling Radio Bearers (SRBs) and used by UEs. Additionally, RRC controls addition, modification, and release of carrier aggregation (CA) and dual-connectivity (DC) configurations for UEs, and performs various security functions such as key management.

[0089] After a UE is powered ON it will be in the RRC IDLE state until an RRC connection is established with the network, at which time the UE will transition to RRC CONNECTED state (e.g., where data transfer can occur). The UE returns to RRC IDLE after the connection with the network is released. In RRCJDLE state, the UE’s radio is active on a discontinuous reception(DRX) schedule configured by upper layers. During DRX active periods (also referred to as “DRX On durations”), an RRC IDLE UE receives SI broadcast in the cell where the UE is camping, performs measurements of neighbor cells to support cell reselection, and monitors a paging channel on PDCCH for pages from 5GC via gNB. An NR UE in RRC IDLE state is not known to the gNB serving the cell where the UE is camping. However, NR RRC includes an RRC_INACTIVE state in which a UE is known (e.g., via UE context) by the serving gNB. RRC INACTIVE has some properties similar to a “suspended” condition used in LTE.

[0090] As mentioned above, RRC also handles configuration of AS security parameters such as integrity protection algorithm, ciphering algorithm, and parameters keySetChangelndicator and nextHopChainingCount used by the UE to determine its AS security keys upon reconfiguration with sync (with key change), RRC connection re-establishment, and RRC connection resume. The integrity protection algorithm is common for SRB1, SRB2, SRB3 (if configured), SRB4 (if configured) and DRBs configured with integrity protection, with the same keyToUse value. The ciphering algorithm is common for SRB1, SRB2, SRB3 (if configured), SRB4 (if configured) and DRBs configured with the same keyToUse value. Neither integrity protection nor ciphering is used for SRBO.

[0091] RRC integrity protection and ciphering are always activated together, i.e., in one message / procedure. RRC integrity protection and ciphering for SRBs are never de-activated. However, it is possible to switch to a 'NULL' ciphering algorithm (neaO). The 'NULL' integrity protection algorithm (niaO) is used only for SRBs and for the UE in limited service mode, as specified in 3GPP TS 33.501 (V18.0.0). When used for SRBs, integrity protection is disabled for DRBs. In case the ’NULL' integrity protection algorithm is used, 'NULL' ciphering algorithm is also used. Additionally, lower layers discard RRC messages for which the integrity protection check has failed and indicate the integrity protection verification check failure to RRC.

[0092] The AS applies four different security keys: one for integrity protection of RRC signaling (KRRCint), one for ciphering of RRC signaling (KRRCenc), one for integrity protection of user data (Kupint) and one for ciphering of user data (Kupenc). All four AS keys are derived from the K§NB key of the gNB, which is based on the KAMF key handled by upper layers as specified in 3GPP TS 33.501 (vl 8.0.0). The integrity protection and ciphering algorithms can only change upon reconfiguration with sync. The four AS keys change upon reconfiguration with sync (if masterKeyUpdate is included), and upon RRC connection re-establishment and RRC connection resume.

[0093] For each DRB or SRB an independent counter (COUNT) is maintained for each direction and is used in an initialization vector (IV) input to ciphering and integrity protection algorithms applied to each packet of data. Specifically, COUNT is used to ensure fresh IVs when other, semi-stable parameters remain the same. However, it is not allowed to use the same COUNT value more than once for a given security key. In order to avoid such re-use, the network may use different RB identities for RB establishments, change the AS security key, or cause the UE to perform an RRC CONNECTED to RRC IDLE / RRC INACTIVE transition and then return to RRC CONNECTED state. The network must ensure that DL IVs are fresh and that the UE can generate fresh UL IVs. For example, since the UE cannot change DRB IDs or initiate re-keying, the gNB must ensure that such actions are taken when the UL COUNT for a DRB approaches wrap-around.

[0094] In order to limit signaling overhead, individual messages / packets include a short PDCP sequence number (PDCP-SN). In addition, the hyper frame number (HFN) is used as an overflow counter mechanism. HFN needs to be synchronized between the UE and the network. Further details are specified in 3GPP TS 38.323 (v!8.0.0). For each SRB, the value provided by RRC to lower layers to derive a five-bit BEARER parameter used as input for ciphering and for integrity protection is the value of the corresponding srb-Identity with the MSBs padded with zeroes.

[0095] As described in 3GPP TS 38.501 (vl 8.4.0), whenever an initial AS security context needs to be established between a UE and a gNB, the AMF and the UE derive K§NB and a Next Hop parameter (NH) from KAMF provided by the AMF. A NH Chaining Counter (NCC) is associated with each KgNB and NH parameter, and each KgNB is associated with the NCC corresponding to the NH value from which the K§NB was derived. At initial setup, K§NB is derived directly from KAMF, and is then considered to be associated with a virtual NH parameter with NCC value equal to zero. At initial setup, the derived NH value is associated with the NCC value one. The UE and the gNB use K§NB to secure the communication between each other, including derivation of the four keys mentioned above.

[0096] Seamless mobility is a key feature of 3GPP radio access technologies (RATs). When the UE moves between the coverage areas of two cells, a serving cell change needs to be performed at some point. Currently, serving cell change is triggered by L3 (e.g., RSRP) measurements and involves RRC signaling to change PCell and PSCell (e.g., when dual connectivity is configured), as well as release / add SCells (e.g., when CA is configured).

[0097] In general, a RAN (e.g., NG-RAN) configures a UE in RRC_CONNECTED state to perform and report radio resource management (RRM) measurements to assist network-controlled mobility decisions, such as for handover from a serving cell to a target cell (e.g., PCell change). Upon the reported measurements meeting a certain condition or threshold, the serving RAN node may send a handover command to the UE, indicating a target cell for the handover. In NR, the handover command is an RRCReconflguration message with a reconflgurationWithSync field. The procedure to perform a handover is sometimes also referredto as “L3 mobility”, as it is controlled by layer 3 (L3, i.e., RRC) and the messages exchanged are part of L3.

[0098] These reconfigurations are prepared in advance by a target RAN node serving the target cell, upon a request from the UE’s serving RAN node. This request is transmitted over the Xn interface when the serving and target RAN nodes are part of the NG-RAN. The reconfiguration provided by the target RAN node contains all information the UE needs to access the target cell, e.g., random access configuration, a new cell radio network temporary identifier (C-RNTI) assigned to the UE in the target cell, and parameters enabling the UE to calculate security keys that it can use when communicating with the target cell (including sending a handover complete message).

[0099] On UE handovers and transitions from RRC INACTIVE to RRC CONNECTED, the basis for K§NB used between the UE and the target RAN node (e.g., gNB) - called KNG-RAN* - is derived from either the currently active KgNB or from the NH parameter. Deriving KNG-RAN* from the currently active KgNB this is referred to as a “horizontal key derivation” while deriving KNG-RAN* from the NH parameter is referred to as “vertical key derivation.” To facilitate horizontal key derivation, the UE must receive an indication of the NH value currently being used by the source RAN node. This indication is an NCC value (e.g., eight bits) that points to an NH value, and is secured by the source RAN node using one or more of the existing AS keys.

[0100] These horizontal and vertical key derivations are illustrated by Figure 4, which shows exemplary security key derivation for HO and other UE mobility procedures. Since NH parameters are only computable by the UE and the AMF, the AMF provides NH parameters to RAN nodes in a way that forward security can be achieved. On handovers with vertical key derivation, the NH is further bound to the target PCI and its DL frequency (ARFCN-DL) before it is used for KgNB in the target RAN node. On handovers with horizontal key derivation, the currently active KgNB is further bound to the target PCI and its frequency ARFCN-DL before it is used for KgNB in the target RAN node.

[0101] In some cases, however, the RAN may use both horizontal and vertical key derivation to achieve desired “key separation” between source and target RAN nodes for a UE handover. Figure 5 shows a signaling diagram for an exemplary two-stage L3 handover for a UE (510) from a source cell provided by a source RAN node (520) to a target cell provided by a target RAN node (530). The source and target RAN nodes are connected via an Xn interface and both are coupled to NFs in the 5GC (AMF / UPF, 540).

[0102] Initially, the source RAN node triggers inter-cell, Xn-based L3 handover of the UE to the target cell provided by the target RAN node. The source RAN node includes a masterKeyUpdate information element (IE) in the handover command to trigger security keyupdate by the UE. During this procedure, the UE and the target RAN node perform horizontal key derivation, which facilitates initial secure communication between UE and target RAN node in the target cell. Subsequently, the target RAN sends a path switch request to AMF / UPF and receives in response a new {NH, NCC} pair for the UE. The target RAN node informs the source RAN node to release its context for the UE and then triggers an intra-cell L3 handover for the UE, during which the UE and the target RAN node perform vertical key derivation based on the new {NH, NCC} pair.

[0103] 3GPP Rel-18 also includes an NR mobility enhancement known as L1 / L2 based intercell mobility or L1 / L2 triggered mobility (LTM). Current L3-based inter-cell mobility involves complete LI and L2 resets, leading to longer latency, increased signaling overhead, and longer interruptions than for intra-cell beam switching. Thus, Rel-18 LTM is intended to facilitate serving cell changes via L1 / L2 signaling that reduces latency, signaling overhead, and interruptions.

[0104] In LTM, a UE is pre-configured by its serving RAN with one RRC configuration per LTM candidate cell, sometimes referred to as an “LTM candidate cell configuration,” which may be part of an “LTM configuration” with additional information. Each LTM candidate cell configuration may be an RRCReconflguration message or a portion thereof, such as one or more lEs / fields / parameters (e.g., CellGroupConflg IE).

[0105] The UE performs measurements on configured LTM candidate cells and transmits corresponding measurement reports to the RAN, which triggers the execution of a LTM cell switch procedure by the UE to one of the configured LTM candidate cells. This triggering is done by transmitting an LTM cell switch command to the UE in lower layer signaling (e.g., MAC CE). Based on this command, the UE connects to the associated LTM candidate cell and uses the previously received RRC configuration for this cell.

[0106] Furthermore, a UE may perform multiple LTM cell switch procedures without being reconfigured by the RAN. For example, after the UE has performed an LTM cell switch from a serving cell to a first target cell (e.g., a first LTM candidate cell), the UE may perform another LTM cell switch from the first target cell to a second target cell (e.g., a second LTM candidate cell) without receiving another RRCReconflguration message in the first target cell. This second LTM cell switch and any further LTM cell switches performed without being reconfigured are often referred to as “subsequent LTM.”

[0107] Since a goal of LTM is to reduce interruption time for UE data transmissions, the UE needs to be ready to communicate with an LTM candidate cell upon (or shortly after) receiving the lower-layer command for LTM execution from the source cell. For example, the UE must be able to transmit UL data or a scheduling request (SR) to the LTM candidate cell and / or monitora DL control channel (e.g., PDCCH) from the LTM candidate cell. In other words, UE needs to know the cell that it is moving to so it can apply the corresponding configuration, including the correct timing alignment and / or transmission configuration indicator (TCI) state for the cell. Likewise, in the case of inter-DU LTM, when the source DU transmits the L1 / L2 signaling for mobility execution, the target DU needs to be prepared for scheduling UL and DL transmissions for the UE in the target cell, and for receiving SR from the UE.

[0108] Accordingly, before receiving an LTM cell switch command, the UE performs early UL and DL synchronization with its configured LTM candidate cells. For early UL synchronization, the UE transmits a contention-free random access (CFRA) preamble towards an LTM candidate cell in response to a physical DL control channel (PDCCH) order received via the source cell. In order to minimize the data interruption of the source cell due to CFRA towards the LTM candidate cell, the UE doesn’t receive a RA response (with TA) from the LTM candidate cell. Instead, the TA for the LTM candidate cell is indicated in a subsequent LTM cell switch command. By obtaining the TA value (or command) in this manner, the UE avoids having to transmit a RA preamble and receive a RA response (RAR) during the LTM cell switch.

[0109] As mentioned above, the LTM cell switch command from the source RAN node (or DU) may be a MAC control element (CE) that includes an identifier (e.g., index) of the corresponding LTM candidate cell configuration previously provided to the UE. The MAC CE may also include an identifier of a beam by which the UE should access the target cell. For example, the beam indication is given as a TCI state identifier (ID) associated with the LTM candidate cell. Upon receiving the LTM cell switch command, the UE monitors PDCCH on the indicated beam of the target cell. In other words, the UE considers the TCI state for the indicated beam / TCI state to be “activated” when performing the LTM cell switch. The UE also applies the LTM candidate cell configuration identified in the MAC CE. Note that since the UE previously performed early UL synchronization, it does not need to perform RA at LTM cell switch.

[0110] However, the MAC layer does not include security mechanisms similar to the AS security keys and algorithms used for RRC signaling. Thus, the LTM cell switch command MAC CE transmitted by the source RAN node is neither encrypted nor integrity protected. Although other layers (e.g., PHY) may try to detect and recover bit and block errors, it is still possible that information in the MAC CE may be corrupted or changed without detection by the MAC layer.

[0111] Rel-18 LTM also support the split CU / DU architecture of Figure 1, including intra-DU and inter-DU / intra-CU LTM cell switches. In the inter-DU / intra-CU scenario, the candidate cell is served by a neighbor DU to the (serving or source) DU that currently provides the UE’s PCell. In the intra-DU scenario, the candidate cell is served by the same DU that currently provides the UE’s PCell (or PSCell, for SCG change in DC). In terms of security, the NCC value does notneed to change for Rel-18 intra-CU LTM since the UE will communicate with the same CU using the same security keys before and after an LTM cell switch.

[0112] 3GPP Rel-19 will support inter-CU LTM between source and candidate cells associated with different CUs. An inter-CU LTM cell switch may require additional UE operations compared to intra-CU LTM cell switch, such as security key update. As such, an inter-CU LTM configuration (or LTM candidate cell configuration) may include the same information as an intra-CU LTM configuration (or LTM candidate cell configuration) as well as one or more of the following:

[0113] • Information needed to perform security key update, e.g., MasterKeyUpdate IE or a RadioBearerConflg IE that includes SecurityConflg with SecurityAlgorithmConfig', • Indication to perform L2 / PDCP re-establishment; and

[0114] • Indication to perform a full configuration, e.g., RRC field fullConfig.

[0115] According to 3GPP TS 38.331 (v!8.4.0), the RRC message field Itm-NoResetID is used to determine if lower layer buffers should be cleared. In particular, if the Itm-NoResetID value received for the target cell is the same as the Itm-NoResetID value the UE has stored for the serving cell, then the UE’s lower-layer buffers need not be cleared during an LTM cell switch. Similar to Itm-NoResetID, 3GPP has defined a new field called Itm-NoSecurityChangelD that indicates whether security needs to be re-established (e.g., security key change) during an LTM cell switch.

[0116] In L3 handover, the NCC value needed by the UE to perform a security key change is provided via RRC with integrity protection based on the current KRRCint. Since LTM execution is controlled by lower layers and does not involve RRC, it is desirable to provide NCC to the UE via lower layers. 3GPP has agreed that, for Rel-19 LTM, the NCC value may be sent unprotected (i.e., in plaintext) in a MAC CE from the RAN to the UE. For example, one candidate MAC CE is the LTM cell switch command, an example of which is shown in Figure 6.

[0117] According to 3GPP TS 38.321 (vl 8.4.0) section 6.1.3.75, this LTM cell switch MAC CE has a variable size based on the “C” bit in Octet 1. In particular, C set to ‘0’ means that Octets 5-7 are not present. Thus, in order to use the five reserved (R) bits in Octet 7 to carry NCC, C must be set to ‘ 1’ indicating that Octets 5-7 are included. However, the information in Octets 5-6 may be irrelevant and need to be discarded by the UE, resulting in undesirable signaling overhead.

[0118] However, it is also possible that the UE attempts to interpret and apply Octets 5-6, which may lead to operational errors. When the RAN sends the MAC CE with NCC occupying the currently reserved bits in Octet 7, the UE may also interpret the fields in Octets 5-6 according to their customary meaning. For example, the UE erroneously concludes that this LTM cell switch procedure includes RA to the target cell, due to the RA-related parameters in Octets 5-6, when in reality no RA is required because the MAC CE also included the TA command in Octets 1-2. Dueto this mismatch, the UE may conclude that the MAC CE provides an invalid configuration and initiate RRC re-establishment (with resulting latency and interruption) rather than proceed with the LTM cell switch. For at least these reasons, the conventional LTM cell switch MAC CE shown in Figure 5 is not suitable for conveying an NCC value to use for UE security key derivation.

[0119] Accordingly, embodiments of the present disclosure address these and related problems, issues, and / or difficulties by flexible and efficient techniques for indicating NCC and / or other security-related information in a MAC CE (e.g., LTM cell switch) sent by a RAN node to a UE. For example, the other security -related information in such a MAC CE may include indication of whether NCC should be used and / or whether a security identifier (e.g., Itm-NoSecurityChangelD) should be used.

[0120] Embodiments of the present disclosure may provide various advantages and / or benefits. Some embodiments may facilitate reuse of the existing seven-octet LTM cell switch MAC CE to include additional security-related information, thereby facilitating security key updates without additional signaling overhead. Other embodiments may be based on larger MAC CEs that convey additional security-related information. Moreover, embodiments may facilitate UE security key updates in conjunction with LTM cell switch without ambiguity by providing new rules or procedures for UE interpreting MAC CE fields. Ini this manner, embodiments may prevent erroneous UE operation in conjunction with LTM cell switch.

[0121] In the present disclosure, the following terms may be used interchangeably: “L1 / L2 based inter-cell mobility”, “L1 / L2 mobility,” “LI -mobility,” “LI based mobility,” “Ll / L2-centric inter-cell mobility,” “L1 / L2 inter-cell mobility,” “inter-cell beam management,” “inter-DU L1 / L2 based inter-cell mobility”, and “L1 / L2 triggered mobility” (or LTM). These terms refer to a scenario in which a UE receives lower layer (i.e., below RRC, such as MAC or PHY) signaling from a network indicating for the UE to change of its serving cell (e.g., PCell) from a source cell to a target cell.

[0122] The content of the lower layer signaling may be referred to as “LTM cell switch command”. Exemplary lower layer signaling includes LI DL control information (DCI) and L2 MAC control element (CE). Compared to conventional RRC signaling, lower layer signaling reduces processing time and interruption time during mobility and may also increase mobility robustness since the network can respond more quickly to changes in the UE’s channel conditions.

[0123] The term “LTM candidate cell” refers to a cell for which the UE is configured for LTM, specifically a cell the UE can move to in a LTM cell switch procedure in response to receiving an LTM cell switch command. An LTM candidate cell may also be referred to herein as “candidate cell”, “(LTM) candidate, “mobility candidate”, “non-serving cell”, “additional cell”, “(LTM) target candidate cell”, “(LTM) target candidate”, and comparable terms. A UE may perform andreport measurements (e.g., CSI measurements) on an LTM candidate cell, based on which the UE’s serving RAN node may make an informed decision about which beam (or TCI state) and / or cell to switch the UE. An LTM candidate cell may be a candidate to be a target PCell or PSCell, or an SCell of a cell group (e.g., MCG SCell). In the case of LTM fast recovery, when a failure is detected and the UE selects an LTM candidate cell, the UE performs an LTM cell switch towards the selected LTM candidate cell (e.g., by applying the associated LTM candidate cell configuration) rather than performing RRC re-establishment.

[0124] The change of serving cell (e.g., PCell) may also lead to a change in other cells (e.g., SCells) of the same cell group, such as when an LTM cell switch command triggers the UE to change to another cell group configuration of the same type (e.g., another MCG). For example, an LTM cell switch may include a change in SpCell (e.g., PCell for MCG, PSCell for SCG) and a change (e.g., addition, modification and / or release) in SCells of the same cell group. This may happen when the command triggers the UE to change to another cell group configuration of the same type (e.g., another SCG configuration).

[0125] Before the UE receives the LTM cell switch command, the UE is configured by the network with one or more “LTM candidate cell configurations” via an RRCReconflguration message. The terms “(LTM) candidate configuration”, “(LTM) candidate target cell configuration”, and “(LTM) target candidate (cell) configuration” may be used interchangeably with LTM candidate cell configuration.

[0126] An LTM candidate cell configuration may be included in an RRC IE such as CellGroupConfig, SpCellConfig, or SCellConfig and / or an embedded RRCReconflguration message for an LTM candidate cell. An LTM candidate cell configuration includes configuration parameters the UE needs to operate in that LTM candidate cell when it performs an LTM cell switch procedure, e.g., upon reception of the LTM cell switch command. As some more specific examples, an LTM candidate cell configuration can include a PCell configuration and one or more SCell configurations of an MCG, or a PSCell configuration and one or more SCell configurations of an SCG. The exact content and / or structure of the IE and / or embedded message for an LTM candidate cell configuration may be called “RRC model for the candidate configuration” or more simply “RRC model”.

[0127] A UE may receive an LTM candidate cell configuration in a complete form or as a delta (or difference) relative to a reference configuration (which may be signaled separately). In the latter case, the actual LTM candidate configuration is a combination of the delta configuration and the reference configuration.

[0128] The lower layer signaling from the RAN may include an identifier (or index) associated with an LTM candidate cell configuration. The identifier may be sent together with an LTM cellswitch command, indicating for the UE to perform an LTM cell switch to the associated LTM candidate cell.

[0129] The term “LTM configuration” (or more generically “mobility configuration”) refers to a data structure that is used for or related to UE mobility procedures such as LTM, and may include one or more of the following elements (non-exclusive):

[0130] • a candidate cell configuration, such as one or more of the following for a mobility (e.g., LTM) candidate cell:

[0131] o lower layer information, such as Ll / PHY configuration, L2 / MAC / RLC configuration, cell group configuration, serving cell configuration, etc.; and

[0132] o higher layer information, such as L3 / RRC parameter and / or timer values, PDCP configuration, radio bearer configuration, L3 / RRC measurement configuration, etc.;

[0133] • a measurement configuration, e.g., measurements for LTM, measurement reports for LTM, CSI resource configuration for LTM, CSI report configuration for LTM, etc.; • a configuration for early DL synchronization, e.g., for early TCI state activation;

[0134] • a configuration for early UL synchronization, e.g., for transmission of PDCCH ordered preamble transmission and reception of timing advance (TA);

[0135] • a configuration for execution of an LTM cell switch procedure according to a given LTM candidate cell configuration (e.g., whether to perform RA, RLC reestablishment, MAC reset, PDCP recovery, etc.).;

[0136] • indication of whether to perform a full and / or complete configuration, e.g., RRC fullConfig field;

[0137] • information needed to perform security key refresh, e.g., RRC MasterKeyUpdate IE or RadioBearerConflg IE including SecurityConflg with Security AlgorithmConfig; and • additional information needed for an inter-CU / gNB LTM cell switch procedure, such as examples mentioned above.

[0138] The term “part of a mobility configuration” may refer to a subset of the elements in the above list, and / or a subset of items comprising any of the elements present (e.g., subset of configurations for DL pre-sync).

[0139] The phrase “LTM cell switch procedure” refers to the process of a UE switching (or changing) from a source cell to a target cell (i.e., an LTM candidate cell) using LTM. An LTM cell switch procedure may also be referred to as “L1 / L2 based inter-cell mobility execution”, “LTM execution”, “dynamic switch”, “LTM switch”, “(LTM) cell switch”, “(LTM) serving cell change”, or “(LTM) cell change”. Similarly, the phrase “switching to an LTM candidate cell configuration” means that the UE applies an LTM candidate cell configuration such that the associated LTM candidate cell becomes its new special cell (SpCell, e.g., PCell for LTM in MCGor PSCell for LTM in SCG) or its new secondary cell (SCell). In other words, an LTM candidate cell can be a candidate for the UE’s PCell, PSCell, or SCell.

[0140] Furthermore, an LTM cell switch may involve a UE switching (or changing) from a source cell group to a target cell group using LTM. For example, this may involve a change in the SpCell for a cell group (e.g., PCell for MCG, PSCell for SCG), a change in SCells of the cell group (e.g., addition, modification, and / or release of one or more SCells), and / or a swap between SpCell and SCell roles for two cells in the same cell group.

[0141] The term “security key” may refer to an integrity protection key for CP, an integrity protection key for UP, an encryption key for CP, an encryption key for UP, or an intermediate key used for derivation of any of these key (e.g., K§NB). The term “security configuration” refers to one or more parameters used to control security key derivation performed by a UE, and may include one or more of the following:

[0142] • a first identifier associated to a candidate cell;

[0143] • a second identifier associated to a source cell the UE is connected to when the mobility procedure is executed;

[0144] • a key set change indicator;

[0145] • a next hop chaining counter (NCC);

[0146] • a non-access stratum (NAS) container (NASC);

[0147] • an indication, indicating that mobility from current serving cell to a certain candidate target cell requires security key refresh;

[0148] • an indication, indicating that mobility towards a certain target cell requires security key refresh (or does not require security key refresh);

[0149] • an indication, indicating that security key refresh is required (or is not required) for subsequent mobility towards a certain cell; and

[0150] • an indication that security key refresh is to be performed without RA.

[0151] An example security configuration is the masterKeyUpdate IE.

[0152] The term “security key refresh,” “security key update,” “AS key refresh” or similar terms refer to a procedure by which a UE changes or updates one or more AS security keys, including during a mobility procedure such as an LTM cell switch procedure. A security key refresh may include at least one of the following operations:

[0153] • UE receives a masterKeyUpdate IE included in a mobility configuration, e.g., in the candidate cell configuration;• When a NAS indication (e.g., NASC) is received masterKeyUpdate IE, the UE forwards the NAS indication to UE NAS layer and updates its NAS security context according to 3GPP TS 33.501 clause 6.9.2.3.4;

[0154] • When a key set change indication (e.g., keySetChangelndicator) is received and / or is set to ‘true’ (e.g., within masterKeyUpdate IE), the UE derives or updates KgNB based on KAMF, as specified in 3GPP TS 33.501;

[0155] • UE derives or updates K§NB for the candidate cell configuration based on the current K§NB or the NH, using the NCC value indicated in the received masterKeyUpdate IE, as specified in 3GPP TS 33.501;

[0156] • UE derives KRRCCIIC and Kupenc associated with a ciphering algorithm (e.g., cipheringAlgorithm indicated in securityAlgorithmConflg), as specified in 3GPP TS 33.501;

[0157] • UE derives KRRCint and Kupint associated with an integrity protection algorithm (e.g., integrityProtAlgorithm indicated in securityAlgorithmConflg), as specified in 3GPP TS 33.501;

[0158] • UE receives a security algorithm configuration included in a mobility configuration, based on which the UE derives UP security keys (e.g., Kupenc and Kupint) and / or CP security keys (e.g., KpRCenc and KRRCint) for encryption and / or integrity protection;

[0159] • UE uses its current security algorithm configuration, based on which the UE derives UP security keys (e.g., Kupenc and Kupint) and / or CP security keys (e.g., KpRCenc and KRRCint) for encryption and / or integrity protection;

[0160] • UE applies the provided ciphering algorithm and associated security key during a PDCP entity re-establishment procedure; and

[0161] • UE applies the provided integrity protection algorithm and associated security key during a PDCP entity re-establishment procedure;

[0162] • UE derives the security key(s) when it receives a mobility configuration, which it may user for a subsequent mobility procedure.

[0163] Some embodiments include methods for a UE configured for mobility between cells in a RAN. Initially, the UE is configured with a first security key (e.g., K§NB) associated with a first RAN node that provides the UE’s serving cell. The first security key may be associated with a first key identifier (e.g., NCCi) and a first parameter (e.g., NH) from which a second security key (e.g., KgNB5) may be derived. For example, in vertical key derivation, the NH is bound to physical cell identity (PCI) and DL frequency (ARFCN-DL) before it is used for the second security key (e.g., KgNB5). The first parameter and / or the second security key may also be associated with a second key identifier (e.g., NCCi+i).The UE receives from the first RAN node one or more mobility candidate configurations for a mobility operation to respective mobility candidate cells provided by a second RAN node. This information may be received, for example, in an RRCReconflguration message, in broadcast SI, NAS signaling, etc. For example, the mobility operation may be an LTM cell switch and the mobility candidate cells may be respective LTM candidate cells. The mobility operation may involve a security update, such as change in security keys and possibly other changes. For example, the mobility operation may be an inter-CU / inter-gNB LTM cell switch.

[0164] In some embodiments, the UE may also be configured by the first RAN node with a first set of security information associated with the one or more mobility candidate cells provided by the second RAN node. This first set of security information may be provided within or together with the mobility candidate configurations.

[0165] The UE then receives from the first RAN node a first message (e.g., command) to execute the mobility operation (i.e., from the UE’s serving cell provided by the first RAN node) to first one of the mobility candidate cells, in accordance with the associated mobility candidate configuration. For example, the first message may be a MAC CE (e.g., LTM cell switch MAC CE), downlink control information (DCI), or an RRC message.

[0166] In conjunction with performing the mobility operation to the first mobility candidate cell, the UE performs a first security update based on the first set of security information. For example, the UE may derive a second security key based on the first set of security information, and possibly based on other information associated with the second RAN node and / or with the first mobility candidate cell (e.g., PCI, DL frequency, etc.).

[0167] In some embodiments, the first message (e.g., MAC CE) may also include a part of the first set of security information, or other security-related information used in the security update. Some examples are discussed below.

[0168] In some embodiments, the first set of security information may include one or more of the following parameters:

[0169] • the first security key associated with the first RAN node (e.g., K§NB);

[0170] • the first key identifier (e.g., NCCi);

[0171] • the first parameter (e.g., NH);

[0172] • identifiers of one or more security algorithms used to calculate security key(s) for the second RAN node;

[0173] • an indication to perform a security update in conjunction with the mobility operation; • to perform a vertical key derivation in conjunction with the mobility operation;

[0174] • to perform a horizontal key derivation in conjunction with the mobility operation;

[0175] • to perform a further security update for the second RAN node after the mobility operation;• one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed; and

[0176] • one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0177] After performing the mobility operation, the first mobility candidate cell becomes the UE’s serving cell. The UE may operate in this serving cell based on the second security key derived in conjunction with the mobility operation.

[0178] In some embodiments, the UE then receives a second message (e.g., command) to perform a second security update, such as another change in security keys and possibly other changes. For example, the second message may be a MAC CE, DCI, or an RRC message. The second message may include a second set of security information, based on which the UE performs the second security update in the serving cell. For example, the UE may derive a third security key based on the second set of security information, and possibly based on other information associated with the second RAN node and / or with the first mobility candidate cell (e.g., PCI, DL frequency, etc.). Unlike the first security update, the second security update is not done in conjunction with a mobility operation. Afterwards, the UE may operate in the serving cell based on the third security key derived based on the second set of security information.

[0179] In some embodiments, the second set of security information may include or indicate one or more of the following parameters:

[0180] • a second security key associated with the second RAN node (e.g., K§NB);

[0181] • a second key identifier (e.g., NCCi);

[0182] • a second parameter (e.g., NH) from which athird security key (e.g., K§NB’) may be derived;

[0183] • identifiers of one or more security algorithms used to calculate security key(s) for the second RAN node;

[0184] • to perform a security update;

[0185] • to perform a vertical key derivation;

[0186] • to perform a horizontal key derivation;

[0187] • one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0188] In some embodiments, after the second security update, the UE may continue to operate in the serving cell according to other (i.e., non-security-related) parameters and / or configurations that were active before the second security update. Put differently, the UE may only modify the security-related parts of its configuration in the serving cell (e.g., the first mobility candidate configuration applied during the mobility operation).

[0189] In other embodiments, after the second security update, the UE may modify, adjust, and / orreconfigure other parameters and / or configurations that were active before the second security update. Put differently, the UE may modify not only the security -related parts but also other parts of its configuration in the serving cell (e.g., the first mobility candidate configuration applied during the mobility operation). In some embodiments, the second message may explicitly indicate whether the UE needs to modify, adjust, and / or reconfigure other parameters and / or configurations that were active before the second security update.

[0190] In some embodiments, the second message may include a set of parameters and / or configurations that overrides corresponding parameters and / or configurations (i.e., for operation in the serving cell provided by the second RAN node)( that the UE currently stores in its memory. For example, if the UE’s current configuration includes field 1 with a current value of “1” and the second message includes a field 1 with a value of “0”, the UE updates its stored value of field 1 from “1” to “0” and subsequently operates in the serving cell according to this new stored value.

[0191] In some embodiments, the first message and / or the second message may be unsecured, such as an unsecured MAC CE discussed in more detail above. In these scenarios, there may be some benefit in limiting the duration in which the UE can receive such an unsecured message. Some embodiments that provide this benefit are discussed below.

[0192] In some embodiments, the UE starts a timer upon performing the mobility operation to the first mobility candidate cell. While the timer is running (i.e., not expired or stopped), the UE may receive the second message in unprotected form from the second RAN node. Upon receiving the second message, the UE stops the timer.

[0193] In some embodiments, while the timer is running (i.e., no unprotected second message has been received), the UE ignores (i.e., does not apply) any protected message from the second RAN node that includes any of the second set of security information. In some variants, the UE may also refrain from performing any security update while the timer is running and no unprotected second message has been received.

[0194] In some embodiments, if the UE receives the unprotected second message after the timer expires, the UE ignores this message and transitions to RRC IDLE state. In some variants, the UE may also indicate a failure and / or a release cause (e.g., ‘other’, ‘connection failure’, ‘security failure’) to upper layers, based on which upper layers trigger NAS recovery procedure. For example, the NAS recovery procedure may be a Registration Area Update (RAU).

[0195] Figures 7-11 show some example MAC CEs that may be utilized as the first message and / or the second message discussed above, according to various embodiments of the present disclosure.

[0196] In particular, Figure 7 shows a structure that is similar to the Rel-18 LTM cell switch MAC CE except for the addition of a new Octet 5, such that it now includes eight octets. This new octetincludes the following fields:

[0197] • NCC - this three-bit field indicates the NexthopChainingCount based on which the UE should derive the NH parameter / key.

[0198] • N - this one-bit field indicates type of key derivation for which NCC should be used. A value of “1” indicates vertical key derivation based on NCC while a value of “0” indicates horizontal key derivation in which the NCC field is disregarded (or may be omitted). • R - four reserved bits.

[0199] Figure 8 shows another eight-octet structure that is similar to the Rel-18 LTM cell switch MAC CE except for the addition of a new Octet 5. In this structure, the one-bit N field is placed in a currently reserved bit in Octet 3, while the NCC field is in the same position as in Figure 7. In this example, there are five reserved bits in new Octet 5.

[0200] Figure 9 shows a single-octet MAC CE that is used only for delivery of the security-related fields N and NCC. In particular, this single octet MAC CE includes the contents of Octet 5 in Figure 7.

[0201] Figure 10 shows a structure that is similar to the Rel-18 LTM cell switch MAC CE except that the one-bit N field is placed in a currently reserved bit in Octet 3 and the two least significant bits (LSBs) of the three-bit NCC field are placed in currently reserved bits in Octet 4.

[0202] Figure 11 shows a structure that is similar to the Rel-18 LTM cell switch MAC CE except that the most significant bit (MSB) of the three-bit NCC field is placed in a currently reserved bit in Octet 3 and the two least significant bits (LSBs) of the three-bit NCC field are placed in currently reserved bits in Octet 4. The one-bit N field is not included in this example.

[0203] One advantage of the examples shown in Figures 10-11 is that Octets 5-7 do not need to be sent when RA is unnecessary, avoiding the problems of UE confusion as discussed above.

[0204] Although LTM cell switch initiated by an LTM cell switch MAC CE is mentioned above as an example of the mobility operation performed by the UE, this mobility operation may also be any of the following:

[0205] • LTM cell switch initiated by cell selection after a fast recovery (e.g. , after radio link failure or LTM cell switch failure);

[0206] • conditional LTM (CLTM) cell switch initiated by fulfillment of execution condition(s);

[0207] • CLTM cell switch initiated by cell selection after a fast recovery (e.g., after radio link failure or LTM cell switch failure);

[0208] • L3 handover;

[0209] • L3 conditional handover (CHO) initiated by fulfillment of execution condition(s);

[0210] • L3 CHO initiated by cell selection after a fast recovery (e.g., after radio link failure or LTM cell switch failure); and• L3 dual active protocol stack (DAPS) handover.

[0211] In cases where the mobility operation is conditional (e.g., CLTM), the first message may be a different type of message than a command sent to trigger a non-conditional mobility operation.

[0212] Other embodiments include complementary methods for a first RAN node configured to provide a serving cell for a UE. Initially, the first RAN node is configured with a first security key (e.g., KgNB) used for secure communications with the UE in the serving cell. The first security key may be associated with a first key identifier (e.g., NCCi) and a first parameter (e.g., NH) from which a second security key (e.g., K§NB’) may be derived. For example, in vertical key derivation, the NH is bound to physical cell identity (PCI) and DL frequency (ARFCN-DL) before it is used for the second security key (e.g., KgNB’). The first parameter and / or the second security key may also be associated with a second key identifier (e.g., NCCi+i).

[0213] The first RAN node sends the UE one or more mobility candidate configurations for a mobility operation to respective mobility candidate cells provided by a second RAN node. This information may be provided, for example, in an RRCReconflguration message, in broadcast SI, NAS signaling, etc. For example, the mobility operation may be an LTM cell switch and the mobility candidate cells may be respective LTM candidate cells. The mobility operation may involve a security update, such as change in security keys and possibly other changes. For example, the mobility operation may be an inter-CU / inter-gNB LTM cell switch.

[0214] In some embodiments, the first RAN node may receive the one or more mobility candidate configurations from the second RAN node prior to sending them to the UE. This may be received in response to a request from the first RAN node. In some embodiments, In some embodiments, the first RAN node may send the second RAN node a notification of the mobility operation by the UE, such as an XnAP LTM SWITCH NOTIFICATION message.

[0215] In some embodiments, the first RAN node may also provide the UE with a first set of security information associated with the one or more mobility candidate cells provided by the second RAN node. This first set of security information may be provided within or together with the mobility candidate configurations. In various embodiments, the first set of security information may include any of the parameters mentioned above in relation to UE embodiments.

[0216] The first RAN node then sends the UE a first message (e.g., command) to execute the mobility operation (i.e., from the UE’s serving cell provided by the first RAN node) to first one of the mobility candidate cells, in accordance with the associated mobility candidate configuration. For example, the first message may be a MAC CE (e.g., LTM cell switch MAC CE), downlink control information (DCI), or an RRC message.

[0217] As mentioned above, in conjunction with performing the mobility operation to the first mobility candidate cell, the UE performs a first security update based on the first set of securityinformation. For example, the UE may derive a second security key based on the first set of security information, and possibly based on other information associated with the second RAN node and / or with the first mobility candidate cell (e.g., PCI, DL frequency, etc.).

[0218] As discussed above, the first message (e.g., MAC CE) may also include a part of the first set of security information, or other security-related information used in the security update. Some examples were discussed above.

[0219] Other embodiments include complementary methods for a second RAN node configured to provide one or more mobility candidate cells for a UE. The second RAN node sends, to a first RAN node that provides a serving cell for the UE, one or more mobility candidate configurations for a mobility operation (i.e., by the UE) to respective mobility candidate cells provided by the second RAN node. This may done in response to a request from the first RAN node.

[0220] The second RAN node determines that the UE has executed the mobility operation to a first one of the mobility candidate cells previously (i.e., as target cell). In some embodiments, this determination is based on receiving from the first RAN node a notification of the mobility operation by the UE, such as an XnAP LTM SWITCH NOTIFICATION message. In some embodiments, this determination is based on receiving an UL message from the UE in the first mobility candidate cell. For example, this UL message can be aRA preamble, a scheduling request (SR) for CP or UP data, an RRCReconfigurationComplete message, a HARQ acknowledgement of a DL message from the second RAN node, etc.

[0221] After the mobility operation, the first mobility candidate cell becomes the UE’s serving cell. The UE may operate in this serving cell based on the second security key derived in conjunction with the mobility operation.

[0222] In some embodiments, the second RAN node then sends the UE a second message (e.g., command) to perform a second security update, such as another change in security keys and possibly other changes. For example, the second message may be a MAC CE, DCI, or an RRC message. The second message may include a second set of security information, based on which the UE performs the second security update in the serving cell. For example, the UE may derive a third security key based on the second set of security information, and possibly based on other information associated with the second RAN node and / or with the first mobility candidate cell (e.g., PCI, DL frequency, etc.). Unlike the first security update, the second security update is not done in conjunction with a mobility operation. Afterwards, the UE may operate in the serving cell based on the third security key derived based on the second set of security information.

[0223] In various embodiments, the second set of security information may include any of the parameters mentioned above in relation to UE embodiments.

[0224] Various features of the embodiments summarized above correspond to various operationsillustrated in Figures 12-14, which show exemplary methods (e.g., procedures) for a UE, a first RAN node, and a second RAN node, respectively. In other words, various features of the operations described below correspond to various embodiments described above. Furthermore, the exemplary methods shown in Figures 12-14 can be used cooperatively to provide various benefits, advantages, and / or solutions to problems described herein. Although Figures 12-14 show specific blocks in particular orders, the operations of the exemplary methods can be performed in different orders than shown and can be combined and / or divided into blocks having different functionality than shown. Optional blocks or operations are indicated by dashed lines.

[0225] In particular, Figure 12 shows an exemplary method (e.g., procedure) for a UE configured for mobility between cells of a RAN, according to various embodiments of the present disclosure. The exemplary method can be performed by a UE (e.g., wireless device) such as described elsewhere herein.

[0226] The exemplary method includes the operations of block 1210, where the UE receives, from a first RAN node via a serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node. The exemplary method also includes the operations of block 1220, where the UE receives from the first RAN node a first message including a command to execute the mobility operation to a first one of the mobility candidate cells. The exemplary method also includes the operations of block 1230, where the UE executes the mobility operation from the serving cell to the first mobility candidate cell. The exemplary method also includes the operations of block 1270, where the UE performs one or more of the following in conjunction with or after the mobility operation:

[0227] • a first security update based on a first set of security information related to the second RAN node, obtained before executing the mobility operation; and

[0228] • a second security update based on a second set of security information related to the second RAN node, obtained after executing the mobility operation.

[0229] In some embodiments, the first message is one of the following: a MAC CE, downlink control information (DCI), or an RRC message. In some of these embodiments, the mobility operation is an LTM cell switch and the first message is an LTM cell switch MAC CE. In other embodiments, the mobility operation is a layer-3 HO and the first message is an RRC handover command.

[0230] In some embodiments, the exemplary method also includes the operations of block 1260, where after executing the mobility operation in block 1230, the UE receives from the second RAN node a second message including a command to perform the second security update. The secondmessage includes the second set of security information. In some of these embodiments, the second message is one of the following: a MAC CE, DCI, or an RRC message.

[0231] In some of these embodiments, the second message is unprotected by either encryption or integrity protection. In some variants of these embodiments, the exemplary method also includes the operations of block 1240, where the UE initiates a message timer after executing the mobility operation. In some further variants, the second security update is performed based on the second set of security information when the unprotected second message is received while the message timer is running. Also, when the unprotected second message is received after the message timer has expired, the exemplary method also includes the operations of block 1280, where the UE refrains from performing the second security update and enters a non-connected state (e.g., RRC IDLE or RRC INACTIVE) with respect to the second RAN node.

[0232] In some further variants, the exemplary method also includes the operations of block 1250, where the UE performs one or more the following operations (labelled with corresponding subblock numbers) while the message timer is running and the unprotected second message has not been received:

[0233] • (1251) discarding a further message that includes at least part of the second set of security information, wherein the further message is protected by encryption and / or integrity protection; and

[0234] • (1252) refraining from performing any security updates with respect to the second RAN node.

[0235] In some embodiments, the first set of security information is included in one or more of the following: the mobility configuration, and the first message. In some of these embodiments, content of the first message is neither encrypted nor integrity-protected.

[0236] In some embodiments, the received mobility configuration is secured based on a first security key associated with the first RAN node, and the first security key is associated with the following: a first key identifier, and a first parameter from which a second security key may be derived. In some of these embodiments, the first key identifier is a next hop chaining count (NCC) and the first parameter is a next hop (NH) parameter.

[0237] In some of these embodiments, performing the first security update based on the first set of security information in block 1270 includes the operations of sub-block 1271, where the UE derives a second security key usable to secure communication with the second RAN node. In some of these embodiments, performing the second security update based on the second set of security information in block 1270 includes the operations of sub-block 1272, where the UE derives a third security key usable to secure communication with the second RAN node. In some variants of these embodiments, at least one of the second security key and the third security key is derived basedon one or more of the following associated with the first mobility candidate cell: a physical cell identity (PCI), and a downlink (DL) carrier frequency.

[0238] In some embodiments, the first set of security information includes or indicates one or more of the following:

[0239] • a first security key associated with the first RAN node;

[0240] • a first key identifier associated with the first security key;

[0241] • a first parameter associated with the first security key;

[0242] • identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0243] • to perform a security update in conjunction with the mobility operation;

[0244] • to perform a vertical key derivation in conjunction with the mobility operation;

[0245] • to perform a horizontal key derivation in conjunction with the mobility operation;

[0246] • to perform a further security update for the second RAN node after the mobility operation;

[0247] • one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed; and

[0248] • one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0249] In some embodiments, the second set of security information includes or indicates one or more of the following:

[0250] • a second security key associated with the second RAN node;

[0251] • a second key identifier associated with the second security key;

[0252] • a second parameter from which a third security key may be derived;

[0253] • identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0254] • to perform a security update;

[0255] • to perform a vertical key derivation;

[0256] • to perform a horizontal key derivation; and

[0257] • one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0258] In some embodiments, the first and second RAN nodes different gNBs, such that the mobility operation is inter-gNB. In other embodiments, the first and second RAN nodes are different CUs, such that the mobility operation is inter-CU.

[0259] In addition, Figure 13 shows an exemplary method (e.g., procedure) for a first RAN node configured to provide a serving cell for a UE, according to various embodiments of the presentdisclosure. The exemplary method can be performed by any appropriate RAN node (e.g., base station, eNB, gNB, ng-eNB, CU, DU, etc.) such as described elsewhere herein.

[0260] The exemplary method includes the operations of block 1320, where the first RAN node sends, to a UE via the serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node. The exemplary method also includes the operations of block 1330, where the first RAN node sends to the UE a first message including a command to execute the mobility operation to a first one of the mobility candidate cells. The mobility configuration and / or the first message includes a first set of security information related to the second RAN node, which configures the UE to perform a first security update in conjunction with the mobility operation.

[0261] In some embodiments, the first message is one of the following: a MAC CE, DCI, or an RRC message. In some of these embodiments, the mobility operation is an LTM cell switch and the first message is an LTM cell switch MAC CE. In other embodiments, the mobility operation is a layer-3 HO and the first message is an RRC handover command.

[0262] In some embodiments, content of the first message is neither encrypted nor integrity-protected. In other words, the first message is not secured when it is sent to the UE. In some embodiments, the mobility configuration is secured based on a first security key associated with the first RAN node, and the first security key is associated with the following: a first key identifier, and a first parameter from which a second security key may be derived. In some of these embodiments, the first key identifier is a next hop chaining count (NCC) and the first parameter is a next hop (NH) parameter.

[0263] In some embodiments, the exemplary method also includes the operations of block 1310, where the first RAN node receives the one or more mobility candidate configurations from the second RAN node, i.e., prior to sending them to the UE. In some embodiments, the exemplary method also includes the operations of block 1340, where after sending the first message in block 1330, the first RAN node sends to the second RAN node a notification of the mobility operation by the UE.

[0264] In various embodiments, the first set of security information can include any of the same information mentioned above in relation to UE embodiments. In some embodiments, the first and second RAN nodes different gNBs, such that the mobility operation is inter-gNB. In other embodiments, the first and second RAN nodes are different CUs, such that the mobility operation is inter-CU.

[0265] In addition, Figure 14 shows an exemplary method (e.g., procedure) for a second RAN node configured to provide a target cell for UE mobility, according to various embodiments of thepresent disclosure. The exemplary method can be performed by a RAN node (e.g., base station, eNB, gNB, ng-eNB, DU, etc.) such as described elsewhere herein.

[0266] The exemplary method includes the operations of block 1420, where the second RAN node determines that the UE has executed a mobility operation from a serving cell provided by a first RAN node to a first one of the mobility candidate cells provided by the second RAN node. The exemplary method also includes the operations of block 1430, where the second RAN node subsequently sends to the UE a second message including a command to perform a second security update based on a second set of security information also included in the second message.

[0267] In some embodiments, the mobility operation is an LTM cell switch. In other embodiments, the mobility operation is an L3 handover. In different embodiments, the second message may be a MAC CE, DCI, or an RRC message. In some embodiments, the second message is unprotected by either encryption or integrity protection. In other words, the second message is not secured when it is sent to the UE.

[0268] In some embodiments, determining that the UE has executed the mobility operation in block 1420 is based on in operations of sub-block 1421, where the second RAN node receives one or more of the following: a notification from the first RAN node, a notification from a DU of the second RAN node, or a message from the UE via the first mobility candidate cell.

[0269] In some embodiments, the exemplary method also includes the operations of block 1410, where the second RAN node sends, to the first RAN node, one or more mobility candidate configurations for the mobility operation to the respective one or mobility candidate cells. The mobility operation is based on a first one of the mobility candidate configurations associated with the first mobility candidate cell.

[0270] In various embodiments, the second set of security information can include any of the same information mentioned above in relation to UE embodiments. In some embodiments, the first and second RAN nodes different gNBs, such that the mobility operation is inter-gNB. In other embodiments, the first and second RAN nodes are different CUs, such that the mobility operation is inter-CU.

[0271] Although various embodiments are described above in terms of methods, techniques, and / or procedures, the person of ordinary skill will readily comprehend that such methods, techniques, and / or procedures can be embodied by various combinations of hardware and software in various systems, communication devices, computing devices, control devices, apparatuses, non-transitory computer-readable media, computer program products, etc.

[0272] Figure 15 shows an example communication system 1500 according to some embodiments. In this example, communication system 1500 includes a telecommunication network 1502 that includes an access network 1504 (e.g., RAN) and a core network 1506, whichincludes one or more core network nodes 1508. Access network 1504 includes one or more access network nodes, such as access network nodes 1510a-b (one or more of which may be generally referred to as network nodes 1510), or any other similar 3GPP access nodes or non-3GPP access points (APs). Some embodiments of the access network 1504 may include more than one access network technology. Access network nodes 1510 of access network 1504 facilitate direct or indirect connection of wireless devices, to the core network 1506 over one or more wireless connections. Such wireless devices may also referred to as user equipment (UEs), with UEs 1512A-D (one or more of which may be generally referred to as UEs 1512) shown by way of example.

[0273] Moreover, such network nodes are not necessarily limited to implementations in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Rather, the network nodes may include disaggregated implementations. For example, in some embodiments, telecommunication network 1502 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in telecommunication network 1502 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in telecommunication network 1502, including one or more access network nodes 1510 and / or core network nodes 1508.

[0274] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e. g. , r App), or any combination thereof (the adj ective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies.

[0275] Access network nodes 1510 facilitate direct or indirect connection of UEs, such as by connecting UEs 1512, to core network 1506 over one or more wireless connections. Example wireless communications over a wireless connection include transmitting and / or receivingwireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, communication system 1500 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. Communication system 1500 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0276] UEs 1512 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with access network nodes 1510 and other communication devices. Similarly, access network nodes 1510 are arranged, capable, configured, and / or operable to communicate directly or indirectly with UEs 1512 and / or with other network nodes or equipment in telecommunication network 1502 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in telecommunication network 1502.

[0277] More specifically, UEs 1512 may send messages, data, and / or other signals to network nodes 1508, 1510 or other elements of the telecommunications network 1502 by transmitting such signals to the relevant device directly without the signals passing through any intervening devices or by transmitting such signals to the relevant device indirectly through an intervening device (or multiple intervening devices) that then transmit the signal to the relevant device. Similarly, network nodes 1508, 1510 may send messages, data, and other signals to UEs 15122, other network nodes 1508, 1510, and other devices in telecommunications network 1502 directly or indirectly. As one specific example, core network node 108 may transmit a particular message to a UE 1512 by transmitting the message to an access network node 1510, which will then transmit the message to the UE 1512. Similarly, core network node 108 may receive a particular message from a UE 1512 by receiving the message from an access network node 1510 that itself received the message from the UE 1512.

[0278] As shown in Figure 15, core network 1506 connects elements of access network 1504 (e.g., one or more of access network nodes 1510) to one or more host computing systems, such as host 1516. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. Core network 1506 may include one or more core network nodes (e.g., 1508) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of core network node 1508. Examplecore network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0279] Host 1516 may be under the ownership or control of a service provider other than an operator or provider of access network 1504 and / or telecommunication network 1502, and may be operated by the service provider or on behalf of the service provider. Host 1516 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0280] As a whole, communication system 1500 of Figure 15 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0281] Moreover, communication system 1500 may be configured to support multiple different standards, protocols, or other rule sets, with individual components supporting all of the relevant rule sets or with different components or sub-systems within the communication system 1500 supporting different standards, protocols, or rule sets. As one example, access network 1504 may contain some access network nodes 1510 that support 3GPP radio access technologies (RAT), such as LTE or NR, while the same (or other) access network nodes 1510 (non-3GPP RATs, such as Wi-Fi or a proprietary RAT. As another example, telecommunications network 1502 may support multiple generations of related communication standards (e.g., 3 GPP 4G and 5G standards) and, as a result, access network 1504 and / or core network 1506 may support multiple generations of related communication standards. Alternately, telecommunications network 1502may include multiple access networks 1504 and / or multiple core networks 1506, which support respective generations of standards.

[0282] In some embodiments, telecommunications network 1502 may support network slicing to provide different logical networks to different devices that are connected to the telecommunications network 1502. For example, the telecommunications network 1502 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs.

[0283] In some examples, one or more of UEs 1512 may be configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 1504 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 1504. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e., being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN / NR dual connectivity (EN-DC).

[0284] According to the example shown in Figure 15, hub 1514 communicates with access network 1504 to facilitate indirect communication between one or more UEs (e.g., 1512C and / or 1512D) and network nodes (e.g., network node 1510b). In some examples, hub 1514 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 1514 may be a broadband router enabling access to core network 1506 for the UEs. As another example, hub 1514 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, access network nodes 1510, or by executable code, script, process, or other instructions in hub 1514.

[0285] As another example, hub 1514 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, hub 1514 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, hub 1514 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 1514 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, hub 1514 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0286] Hub 1514 may have a constant / persistent or intermittent connection to network node 1510b. Hub 1514 may also allow for a different communication scheme and / or schedule betweenhub 1514 and UEs (e.g., 1512C and / or 1512D), and between hub 1514 and core network 1506. In other examples, hub 1514 is connected to core network 1506 and / or one or more UEs via a wired connection. Moreover, hub 1514 may be configured to connect to an M2M service provider over access network 1504 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with access network nodes 1510 while still connected via hub 1514 via a wired or wireless connection. In some embodiments, hub 1514 may be a dedicated hub -that is, a hub whose primary function is to route communications to / from the UEs from / to network node 1510b. In other embodiments, hub 1514 may be anon-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1510b, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0287] In some embodiments, any of UEs 1512 may be configured to perform operations attributed to a UE in various methods or procedures described above, including the exemplary method shown in Figure 12. In some embodiments, any of access network nodes 1510 may be configured to perform operations attributed to a RAN node in various methods or procedures described above, including the exemplary methods shown in Figures 13-14.

[0288] Figure 16 shows another example communication system 1600 according to some embodiments. In this example, communication system 1600 includes multiple access points (APs) (e.g., APs 1610A-D) and multiple wireless devices 1612A-E, which may also be referred to in this context as stations (STAs) 1612A-E (or collectively as STAs 1612).

[0289] Each STA 1612A-E connect through a radio link to one of APs 1610. For example, depending on location or channel conditions experienced by a particular STA, the STA may select an appropriate AP and basic service set (BSS) for establishing the radio link. The radio link may be based on one or more orthogonal frequency-division multiplexing (OFDM) carriers from a frequency spectrum that is shared on the basis of a contention-based mechanism, e.g., an unlicensed or license exempt band like 2.4 GHz Industrial, Scientific, and Medical (ISM) band, 5-GHzband, 6-GHz band, 60-GHzband, etc. In the specific example shown, STA 1612Ais served by AP 1610A in a first BSS 1620A, STA 1610B-C are served by AP 1610B in a second BSS 1620B, STA 1612D is served by AP 1610C in a third BSS 1620C, and STA 1612E is served by AP 1610D in a fourth BSS 1620D.

[0290] STAs 1612 may be non-AP STAs and correspond to various kinds of wireless devices such as user terminals, mobile or stationary computing devices, smartphones, laptop computers, desktop computers, tablet computers, gaming devices, head-mounted displays (HMDs) for Augmented Reality (AR) or Virtual Reality (VR), smart home devices, printers, multimedia devices, data storage devices, etc.As illustrated, APs 1610 may be connected to a data network 1630, enabling each AP to provide data connectivity between STAs 1612 and other entities in data network 1630 (e.g., servers, service providers, data sources, data sinks, user terminals, etc.). Accordingly, a radio link established between a particular STA 1612 and its serving AP 1610 may be used for providing various kinds of services to STA 1612, such as voice, multimedia, data, etc. Such services may be based on applications that are executed on STA 1612 and / or on a device linked to STA 1612.

[0291] In the example shown in Figure 16, data network 1630 includes application service platform 1632, with which application(s) executed on any of STAs 1612 (and / or on one or more other devices linked to STAs 1612) may communicate via the respective radio links between STAs 1612 and their respective serving APs 1610. Such communication may facilitate efficient utilization of the corresponding service(s) at STA 1612.

[0292] In some embodiments, any of STAs 1612 may be configured to perform operations attributed to a UE in various methods or procedures described above, including the exemplary method shown in Figure 12. In some embodiments, any of APs 1610 may be configured to perform operations attributed to a RAN node in various methods or procedures described above, including the exemplary methods shown in Figures 13-14.

[0293] Figure 17 shows an example wireless device 1700 according to some embodiments. Wireless device 1700 may represent any of various examples including, but not limited to, smart phones, mobile phones, cellular phones, voice over IP (VoIP) phones, wireless local loop phones, desktop computers, personal digital assistants (PDAs), wireless cameras, gaming consoles or devices, music storage devices, playback appliances, wearable devices, wireless endpoints, mobile stations, tablets, laptops, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart devices, wireless customer-premise equipment (CPE), vehicles, vehicle-mounted or vehicle embedded / integrated wireless devices, etc. Other examples include any user equipment (UE) identified by 3GPP, including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0294] A wireless device may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, a wireless device may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a wireless device may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a wireless device may represent a device that is not intended for sale to,or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0295] Wireless device 1700 includes processing circuitry 1702 that is operatively coupled via a bus 1704 to an input / output interface 1706, a power source 1708, a memory 1710, a communication interface 1712, and / or one or more other components not explicitly shown. Moreover, certain wireless devices may utilize all or a subset of the components shown in Figure 17. The level of integration between the components may vary from one wireless device to another wireless device, and one or more of the components explicitly shown in Figure 17 may be integrated wholly or partially with other components not explicitly shown. Further, certain wireless devices may contain multiple instances of a particular component (e.g., processors, memories, transceivers, transmitters, receivers, etc.).

[0296] Processing circuitry 1702 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in memory 1710. Processing circuitry 1702 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, processing circuitry 1702 may include multiple central processing units (CPUs).

[0297] In the example shown in Figure 17, input / output interface 1706 may be configured to provide interface(s) to input device(s), output device(s), or some combination thereof. Example output devices include speakers, sound cards, video cards, displays, monitors, printers, actuators, emitters, smartcards, etc., or some combination thereof. Example input devices include atouch-(or presence-) sensitive displays, cameras (e.g., digital camera, video camera, web camera, etc.), microphones, sensors, mice, trackballs, directional pads, trackpads, scroll wheels, smartcards, etc., or some combination thereof.

[0298] As a more specific example, presence-sensitive displays may include a capacitive or resistive touch sensor to sense input from a user. As other more specific examples, sensors may include an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or some combination thereof. In some variants, an output device may use the same interface port (or same port type) as an input device. As an example of these variants, a Universal Serial Bus (USB) port may be used as an input device and an output device.In some embodiments, power source 1708 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. Power source 1708 may further include power circuitry for delivering power from power source 1708 itself, and / or an external power source, to the various parts of wireless device 1700 via input circuitry or an interface such as an electrical power cable. Power circuitry may perform any formatting, converting, or other modification to the power from power source 1708 to make the power suitable for the respective components of wireless device 1700 to which power is supplied.

[0299] Memory 1710 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, memory 1710 includes one or more programs 1714, such as an operating system, web browser application, widgets, a gadget engine, etc. and corresponding data 1716. Memory 1710 may store, for use by wireless device 1700, one or more specific operating systems or combinations thereof.

[0300] Memory 1710 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ Memory 1710 may allow wireless device 1700 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in memory 1710, which may be or comprise a device-readable storage medium.

[0301] Processing circuitry 1702 may be configured to communicate with an access network or other network using communication interface 1712. Communication interface 1712 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1722. Communication interface 1712 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another devicecapable of wireless communication (e.g., another wireless device or a network node in an access network). Each transceiver may include a transmitter 1718 and / or a receiver 1720 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, transmitter 1718 and receiver 1720 may be coupled to one or more antennas (e.g., antenna 1722) and may share circuit components, software, or firmware, or alternatively be implemented separately.

[0302] In the example shown in Figure 17, communication interface 1712 may support and / or provide cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communication (e.g., Bluetooth, near-field communication), location-based communication (e.g., use of the global navigation satellite system, GNSS, to determine location), etc., or any combination thereof. Communications may be implemented according to one or more protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), orthogonal frequency division multiplexing or multiple access (OFDM / OFDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / intemet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0303] In some embodiments, wireless device 1700 may output data captured by its sensors through its communication interface 1712 to a network node via a wireless connection, such as shown in Figures 15-16. In some variants, the wireless connection may be through another wireless device of similar or different type. Output of the captured sensor data may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., an alert is sent when moisture is detected), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0304] In some embodiments, wireless device 1700 may include an actuator, a motor, or a switch related to a communication interface configured to receive wireless input from a network node via a wireless connection. In some variants, the states of the actuator, motor, or switch may change in response to the received wireless input. For example, the UE may include a motor that adjusts control surfaces or rotors of a unmanned aerial vehicle (UAV, e.g., drone) in flight according to the received input, or adjusts a robotic arm performing a medical procedure according to the received input.

[0305] When in the form of an Internet of Things (loT) device, wireless device 1700 may be used in one or more application domains such as wearable technology, extended industrial application, and healthcare. As some non-limiting example, such an loT device may include (or be embeddedin) a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a headmounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, a UAV, and a medical device (e.g., heart rate monitor, remote controlled surgical robot, etc.). When arranged as an loT device, wireless device 1700 may include circuitry and / or software associated with its intended application as well as other components such as described above for more generic embodiments of wireless device 1700.

[0306] As another example loT-related application, wireless device 1700 may include (or be embedded in) a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to other wireless devices and / or to network nodes in a communication network. As a more specific example, wireless device 300 may be an M2M device, which may also be referred to as a machine-type communication (MTC) device in 3GPP vocabulary. Such an M2M device may implement the 3GPP NB-IoT standard. As another example loT-related application, wireless device 1700 may be embedded in a vehicle (e.g., passenger car, motorcycle, bus, truck, ship, airplane, etc.) or in other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0307] In practice, any number of wireless devices (e.g., 1700) may be used together in a single use case. For example, a first wireless device may be or be integrated in a UAV and provide the UAV’s speed information (e.g., obtained through a speed sensor) to a second wireless device that is a remote controller operating the UAV. When the user makes changes from the remote controller, the first wireless device may adjust the throttle on the UAV (e.g., by controlling an actuator) to increase or decrease the UAV’s speed. The first and / or the second wireless devices may include more than the specific functionalities described above. For example, a wireless device may include a sensor and an actuator, and handle communication of data for both the sensor and the actuator.

[0308] In some embodiments, wireless device 1700 may be configured to perform operations attributed to a UE in various methods or procedures described above, including the exemplary method shown in Figure 12.Figure 18 shows an example network node 1800 according to some embodiments. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (e.g., radio base stations, Node Bs, eNBs, gNBs), and O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU). Network node 1800 may be considered as a type of network equipment (in contrast to user equipment, UE).

[0309] Network nodes may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. Network node 1800 may be a relay node or a relay donor node controlling a relay. Network node 1800 may include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0310] Other examples of network nodes (such as 1800) include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0311] Network node 1800 includes processing circuitry 1802, memory 1804, communication interface 1806, and power source 1808. Network node 1800 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. For example, the specific components shown in Figure 18 may represent or include physical components common to or shared by one or more of the other elements of network node 1800.

[0312] In certain scenarios in which network node 1800 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, network node 1800 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memories 1804 for different RATs) and some components may be reused (e.g., oneantenna 1810 may be shared by different RATs). Network node 1800 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1800, e.g., GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID), Bluetooth, etc. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1800.

[0313] Processing circuitry 1802 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other components (e.g., memory 1804) to provide the functionality of network node 1800.

[0314] In some embodiments, processing circuitry 1802 may include a system on a chip (SOC). In some embodiments, processing circuitry 1802 includes radio frequency (RF) transceiver circuitry 1812 and / or baseband processing circuitry 1814. In some embodiments, RF transceiver circuitry 1812 and / or baseband processing circuitry 1814 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1812 and / or baseband processing circuitry 1814 may be on the same chip or set of chips, boards, or units.

[0315] Memory 1804 may include any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by processing circuitry 1802. Memory 1804 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions (collectively denoted computer program 1804A, which may be in the form of a computer program product) capable of being executed by processing circuitry 1802 and utilized by network node 1800. Memory 1804 may be used to store any calculations made by processing circuitry 1802 and / or any data received via communication interface 1806. In some embodiments, processing circuitry 1802 and memory 1804 is integrated.

[0316] Communication interface 1806 may be used for wired or wireless communication of signaling and / or data between network node 1800, an access network, a core network, and / or wireless device(s). As illustrated, communication interface 1806 comprises port(s) / terminal(s)1816 to send and receive data, for example to and from a network over a wired connection. Communication interface 1806 also includes radio front-end circuitry 1818 that may be coupled to, or in certain embodiments a part of, antenna 1810. Radio front-end circuitry 1818 comprises filters 1820 and amplifiers 1822. Radio front-end circuitry 1818 may be connected to an antenna 1810 and processing circuitry 1802. The radio front-end circuitry may be configured to condition signals communicated between antenna 1810 and processing circuitry 1802. Radio front-end circuitry 1818 may receive digital data that is to be sent out to other network nodes or wireless devices via a wireless connection. Radio front-end circuitry 1818 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1820 and / or amplifiers 1822. The radio signal may then be transmitted via antenna 1810. Similarly, when receiving data, antenna 1810 may collect radio signals which are then converted into digital data by radio front-end circuitry 1818. The digital data may be passed to processing circuitry 1802. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0317] In certain alternative embodiments, network node 1800 does not include separate radio front-end circuitry 1818, instead, processing circuitry 1802 includes radio front-end circuitry and is connected to antenna 1810. Similarly, in some embodiments, all or some of RF transceiver circuitry 1812 is part of communication interface 1806. In still other embodiments, communication interface 1806 includes one or more ports or terminals 1816, radio front-end circuitry 1818, and RF transceiver circuitry 1812, as part of a radio unit (not shown), and communication interface 1806 communicates with baseband processing circuitry 1814, which is part of a digital unit (not shown).

[0318] Antenna 1810 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. Antenna 1810 may be coupled to radio front-end circuitry 1818 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, antenna 1810 is separate from network node 1800 and connectable to network node 1800 through one or more interfaces or ports.

[0319] Antenna 1810, communication interface 1806, and / or processing circuitry 1802 may be configured to perform various receiving and / or obtaining operations described herein as being performed by a network node. Any information, data and / or signals may be received from a wireless device, another network node, and / or any other network equipment. Similarly, antenna 1810, communication interface 1806, and / or processing circuitry 1802 may be configured to perform any transmitting operations described herein as being performed by a network node. Any information, data and / or signals may be transmitted to a wireless device, another network node, and / or any other network equipment.Power source 1808 provides power to the various components of network node 1800 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 1808 may further comprise, or be coupled to, power management circuitry to supply the components of network node 1800 with power for performing the functionality described herein. For example, network node 1800 may be connectable to an external power source (e.g., generator, power grid, electrical outlet, etc.) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of power source 1808. As another example, power source 1808 may include a battery or battery pack that is connected to, or integrated with, power circuitry. Such a battery or battery pack may provide backup power should the external power source fail.

[0320] Embodiments of network node 1800 may include additional components beyond those shown in Figure 18 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, network node 1800 may include user interface equipment to allow input of information into network node 1800 and to allow output of information from network node 1800. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 1800.

[0321] In some embodiments, network node 1800 may be configured to perform operations attributed to a RAN node in various methods or procedures described above, including the exemplary methods shown in Figures 13-14.

[0322] Figure 19 shows an example virtualization environment 1900 in which some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1900 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 1900 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface.Applications 1902 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1900 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein. For example, one or more virtual nodes 1902 may be configured to perform operations attributed to a RAN node in various methods or procedures described above, including the exemplary methods shown in Figures 13-14.

[0323] Hardware 1904 may include processing circuitry, memory that stores software and / or instructions (collectively denoted computer program 1904A, which may be in the form of a computer program product) executable by the processing circuitry, and other hardware devices such as a network interface, input / output interface, etc. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1906 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1908A-B (one or more of which may be generally referred to as VMs 1908), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. Virtualization layer 1906 may present a virtual operating platform that appears like networking hardware to the VMs 1908.

[0324] VMs 1908 may include virtual processing resources, virtual memory and / or storage, virtual networking and / or communication interfaces, etc., and may be run by a corresponding virtualization layer 1906. Different instances of a virtual appliance 1902 may be implemented on one or more VMs 1908, in various ways. In this context, hardware virtualization may also be referred to as network function virtualization (NFV), which may be used to consolidate many network equipment types onto commercial off-the-shelf (COTS) hardware such as server hardware, physical switches, physical storage, etc.. Such equipment may be located in data centers, customer premises, etc.

[0325] In the context of NFV, each VM 1908 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each VM 1908, and that part of hardware 1904 which executes the particular VM (e.g., VM-dedicated hardware or hardware shared with other VMs), forms a separate virtual network element. Further in the context of NFV, a virtual network function (NF) may be responsible for handling specific NFs that run in one or more VMs 1908 on top of hardware 1904 and that corresponds to a particular application 1902.

[0326] Hardware 1904 may be implemented in a standalone network node with generic or specific components. Hardware 1904 may implement some functions via virtualization. Alternatively, hardware 1904 may be part of a larger cluster of hardware (e.g., in a data center or customer premises) where many hardware nodes are managed cooperatively by a management and orchestration function 1910, which may oversee lifecycle management (LCM) of applications1902. In some embodiments, hardware 1904 may be coupled to one or more radio units, each of which may include one or more transmitters and / or one or more receivers and may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1912 which may alternatively be used for communication between hardware nodes and radio units.

[0327] The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

[0328] The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and / or electronic devices and can include, for example, electrical and / or electronic circuitry, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and / or displaying functions, and so on, as such as those that are described herein.

[0329] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure.As described herein, device and / or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and / or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person.

[0330] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0331] In addition, certain terms used in the present disclosure, including the specification and drawings, may be used synonymously in certain instances (e.g., “data” and “information”). It should be understood that although such terms may be used synonymously herein, there may be instances when such terms are not intended to be used synonymously.

[0332] Embodiments of the techniques and apparatus described herein also include, but are not limited to, the following enumerated examples:

[0333] Al. A method for a user equipment (UE) configured for mobility between cells of a radio access network (RAN), the method comprising:

[0334] receiving, from a first RAN node via a serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node; receiving from the first RAN node a first message including a command to execute the mobility operation to a first one of the mobility candidate cells; and executing the mobility operation from the serving cell to the first mobility candidate cell;

[0335] and

[0336] performing one or more of the following in conjunction with or after the mobility

[0337] operation:a first security update based on a first set of security information related to the second RAN node, obtained before executing the mobility operation; and a second security update based on a second set of security information related to the second RAN node, obtained after executing the mobility operation.

[0338] Ala. The method of embodiment Al, wherein the first message is one of the following: a medium access control (MAC) control element (CE), downlink control information (DCI), or a radio resource control (RRC) message.

[0339] Alb. The method of embodiment Ala, wherein one of the following applies:

[0340] the mobility operation is a layer- l / layer-2 triggered intercell mobility (LTM) cell switch and the first message is an LTM cell switch MAC CE; or

[0341] the mobility operation is a layer-3 handover (HO) and the first message is an RRC handover command.

[0342] A2. The method of any of embodiments Al-Alb, further comprising, after executing the mobility operation, receiving from the second RAN node a second message including a command to perform the second security update, wherein the second message includes the second set of security information.

[0343] A2c. The method of embodiment A2, wherein the second message is one of the following: a medium access control (MAC) control element (CE), downlink control information (DCI), or a radio resource control (RRC) message.

[0344] A2b. The method of any of embodiments A2-A2a, wherein the second message is unprotected by either encryption or integrity protection.

[0345] A2c. The method of embodiment A2b, further comprising initiating a message timer after executing the mobility operation.

[0346] A2d. The method of embodiment A2c, wherein:

[0347] the second security update is performed based on the second set of security information when the unprotected second message is received while the message timer is running; and

[0348] the method further comprises, when the unprotected second message is received after themessage timer has expired, refraining from performing the second security update and entering a non-connected state with respect to the second RAN node.

[0349] A2e. The method of embodiment A2c-A2d, further comprising performing one or more the following while the message timer is running and the unprotected second message has not been received:

[0350] discarding a further message that includes at least part of the second set of security information, wherein the further message is protected by encryption and / or integrity protection; and

[0351] refraining from performing any security updates with respect to the second RAN node.

[0352] A3. The method of any of embodiments Al-A2e, wherein the first set of security information is included in one or more of the following: the mobility configuration, and the first message.

[0353] A3a. The method of embodiment A3, wherein content of the first message is neither encrypted nor integrity -protected.

[0354] A4. The method of any of embodiments Al -A3, wherein the received mobility configuration is secured based on a first security key associated with the first RAN node, and the first security key is associated with the following: a first key identifier, and a first parameter from which a second security key may be derived.

[0355] A4a. The method of embodiment A4, wherein the first key identifier is a next hop chaining count (NCC) and the first parameter is a next hop (NH) parameter.

[0356] A4b. The method of any of embodiments A4-A4b, wherein:

[0357] performing the first security update based on the first set of security information comprises deriving a second security key usable to secure communication with the second RAN node; and

[0358] performing the second security update based on the second set of security information comprises deriving a third security key usable to secure communication with the second RAN node.

[0359] A4c. The method of embodiment A4b, wherein at least one of the second security key and the third security key is derived based on one or more of the following associated with the firstmobility candidate cell: a physical cell identity (PCI), and a downlink (DL) carrier frequency.

[0360] A5. The method of any of embodiments Al-A4c, wherein the first set of security information includes one or more of the following:

[0361] a first security key associated with the first RAN node;

[0362] a first key identifier associated with the first security key;

[0363] a first parameter associated with the first security key;

[0364] identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0365] an indication to perform a security update in conjunction with the mobility operation; an indication to perform a vertical key derivation in conjunction with the mobility operation;

[0366] an indication to perform a horizontal key derivation in conjunction with the mobility operation;

[0367] an indication to perform a further security update for the second RAN node after the mobility operation;

[0368] one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed; and

[0369] one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed.

[0370] A6. The method of any of embodiments A1-A5, wherein the second set of security information includes one or more of the following parameters:

[0371] a second security key associated with the second RAN node;

[0372] a second key identifier associated with the second security key;

[0373] a second parameter from which a third security key may be derived;

[0374] identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0375] an indication to perform a security update;

[0376] an indication to perform a vertical key derivation;

[0377] an indication to perform a horizontal key derivation;

[0378] one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0379] A7. The method of any of embodiments A1-A6, wherein one of the following applies:the first and second RAN nodes different gNBs, such that the mobility operation is inter- gNB; or

[0380] the first and second RAN nodes are different centralized units (CUs), such that the mobility operation is inter-CU.

[0381] Bl . A method for a first radio access network (RAN) node configured to provide a serving cell for user equipment (UEs), the method comprising:

[0382] sending, to a UE via the serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node; and sending to the UE a first message including a command to execute the mobility operation to a first one of the mobility candidate cells,

[0383] wherein one or more of the following includes a first set of security information related to the second RAN node, which configures the UE to perform a first security update in conjunction with the mobility operation: the mobility configuration, and the first message.

[0384] Bia. The method of embodiment Bl, wherein the first message is one of the following: a medium access control (MAC) control element (CE), downlink control information (DCI), or a radio resource control (RRC) message.

[0385] Bib. The method of embodiment Bia, wherein one of the following applies:

[0386] the mobility operation is a layer- l / layer-2 triggered intercell mobility (LTM) cell switch and the first message is an LTM cell switch MAC CE; or

[0387] the mobility operation is a layer-3 handover (HO) and the first message is an RRC handover command.

[0388] B2. The method of any of embodiments Bl-Blb, wherein content of the first message is neither encrypted nor integrity -protected.

[0389] B3. The method of any of embodiments B1-B2, wherein the mobility configuration is secured based on a first security key associated with the first RAN node, and the first security key is associated with the following: a first key identifier, and a first parameter from which a second security key may be derived.B3a. The method of embodiment B3, wherein the first key identifier is a next hop chaining count (NCC) and the first parameter is a next hop (NH) parameter.

[0390] B4. The method of any of embodiments Bl-B3a, further comprising receiving the one or more mobility candidate configurations from the second RAN node.

[0391] B5. The method of any of embodiments B1-B4, further comprising, after sending the first message, sending to the second RAN node a notification of the mobility operation by the UE.

[0392] B6. The method of any of embodiments B1-B5, wherein the first set of security information includes one or more of the following:

[0393] a first security key associated with the first RAN node;

[0394] a first key identifier associated with the first security key;

[0395] a first parameter associated with the first security key;

[0396] identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0397] an indication to perform a security update in conjunction with the mobility operation; an indication to perform a vertical key derivation in conjunction with the mobility operation;

[0398] an indication to perform a horizontal key derivation in conjunction with the mobility operation;

[0399] an indication to perform a further security update for the second RAN node after the mobility operation;

[0400] one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed; and

[0401] one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed.

[0402] B7. The method of any of embodiments B1-B6, wherein one of the following applies:

[0403] the first and second RAN nodes different gNBs, such that the mobility operation is inter- gNB; or

[0404] the first and second RAN nodes are different centralized units (CUs), such that the mobility operation is inter-CU.

[0405] Cl . A method for a second radio access network (RAN) node configured to provide one ormore mobility candidate cells for a user equipment (UE), the method comprising: determining that the UE has executed a mobility operation from a serving cell provided by a first RAN node to a first one of the mobility candidate cells provided by the second RAN node; and

[0406] subsequently sending to the UE a second message including a command to perform a second security update based on a second set of security information also included in the second message.

[0407] C2. The method of embodiment Cl, further comprising sending, to the first RAN node, one or more mobility candidate configurations for the mobility operation to the respective one or mobility candidate cells, wherein the mobility operation is based on a first one of the mobility candidate configurations associated with the first mobility candidate cell.

[0408] C3. The method of any of embodiments C1-C2, wherein the mobility operation is one of the following applies: a layer-l / layer-2 triggered intercell mobility (LTM) cell switch, or s a layer-3 handover (HO).

[0409] C4. The method of any of embodiments C1-C3, wherein the second message is one of the following: a medium access control (MAC) control element (CE), downlink control information (DCI), or a radio resource control (RRC) message.

[0410] C5. The method of any of embodiments C1-C4, wherein the second message is unprotected by either encryption or integrity protection.

[0411] C6. The method of any of embodiments C1-C5, wherein determining that the UE has executed the mobility operation is based on receiving one or more of the following: a notification from the first RAN node, a notification from a distributed unit (DU) of the second RAN node, or a message from the UE via the first mobility candidate cell.

[0412] C7. The method of any of embodiments C1-C6, wherein the second set of security information includes one or more of the following parameters:

[0413] a second security key associated with the second RAN node;

[0414] a second key identifier associated with the second security key;

[0415] a second parameter from which a third security key may be derived;identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;

[0416] an indication to perform a security update;

[0417] an indication to perform a vertical key derivation;

[0418] an indication to perform a horizontal key derivation;

[0419] one or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

[0420] C8. The method of any of embodiments C1-C7, wherein one of the following applies:

[0421] the first and second RAN nodes different gNBs, such that the mobility operation is inter- gNB; or

[0422] the first and second RAN nodes are different centralized units (CUs), such that the mobility operation is inter-CU.

[0423] DI. User equipment (UE) configured for mobility between cells of a radio access network (RAN), the UE comprising:

[0424] communication interface circuitry configured to communicate with RAN nodes; and processing circuitry operatively coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the methods of any of embodiments A1-A7.

[0425] D2. User equipment (UE) configured for mobility between cells of a radio access network (RAN), the UE being further configured to perform operations corresponding to the methods of any of embodiments A1-A7.

[0426] D3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of user equipment (UE) configured for mobility between cells of a radio access network (RAN), configure the UE to perform operations corresponding to the methods of any of embodiments A1-A7.

[0427] D4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of user equipment (UE) configured for mobility between cells of a radio access network (RAN), configure the UE to perform operations corresponding to the methods of any of embodiments A1-A7.El . A first radio access network (RAN) node configured to provide a serving cell for user equipment (UEs), the first RAN node comprising:

[0428] communication interface circuitry configured to communicate with UEs and with other RAN nodes; and

[0429] processing circuitry operatively coupled to the communication interface circuitry, whereby the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the methods of any of embodiments B1-B7.

[0430] E2. A first radio access network (RAN) node configured to provide a serving cell for user equipment (UEs), the first RAN node being further configured to perform operations corresponding to the methods of any of embodiments B1-B7.

[0431] E3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a first radio access network (RAN) node configured to provide a serving cell for user equipment (UEs), configure the first RAN node to perform operations corresponding to the methods of any of embodiments B1-B7.

[0432] E4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a first radio access network (RAN) node configured to provide a serving cell for user equipment (UEs), configure the first RAN node to perform operations corresponding to the methods of any of embodiments B1-B7.

[0433] Fl. A second radio access network (RAN) node configured to provide one or more mobility candidate cells for user equipment (UEs), the second RAN node comprising:

[0434] communication interface circuitry configured to communicate with UEs and with other RAN nodes; and

[0435] processing circuitry operatively coupled to the communication interface circuitry, whereby the processing circuitry and the communication interface circuitry are configured to perform operations corresponding to the methods of any of embodiments C1-C8.

[0436] F2. A second radio access network (RAN) node configured to provide one or more mobility candidate cells for user equipment (UEs), the second RAN node being further configured toperform operations corresponding to the methods of any of embodiments C1-C8.

[0437] F3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of a second radio access network (RAN) node configured to provide one or more mobility candidate cells for user equipment (UEs), configure the second RAN node to perform operations corresponding to the methods of any of embodiments C1-C8.

[0438] F4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of a second radio access network (RAN) node configured to provide one or more mobility candidate cells for user equipment (UEs), configure the second RAN node to perform operations corresponding to the methods of any of embodiments C1-C8.

Claims

CLAIMS1. A method for a user equipment, UE, configured for mobility between cells of a radio access network, RAN, the method comprising:receiving (1210), from a first RAN node via a serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node;receiving (1220) from the first RAN node a first message including a command to execute the mobility operation to a first one of the mobility candidate cells; and executing (1230) the mobility operation from the serving cell to the first mobility candidate cell; andperforming (1270) one or more of the following in conjunction with or after the mobility operation:a first security update based on a first set of security information related to the second RAN node, obtained before executing the mobility operation; and a second security update based on a second set of security information related to the second RAN node, obtained after executing the mobility operation.

2. The method of claim 1, wherein the first message is one of the following: a medium access control, MAC, control element, CE; downlink control information, DCI; or a radio resource control, RRC, message.

3. The method of claim 2, wherein one of the following applies:the mobility operation is a layer- l / layer-2 triggered intercell mobility, LTM, cell switch and the first message is an LTM cell switch MAC CE; orthe mobility operation is a layer-3 handover and the first message is an RRC handover command.

4. The method of any of claims 1-3, further comprising, after executing (1230) the mobility operation, receiving (1260) from the second RAN node a second message including a command to perform the second security update, wherein the second message includes the second set of security information.

5. The method of claim 4, wherein the second message is one of the following: a medium access control, MAC, control element, CE; downlink control information, DCI; or a radio resource control, RRC, message.

6. The method of any of claims 4-5, wherein the second message is unprotected by either encryption or integrity protection.

7. The method of claim 6, further comprising initiating (1240) a message timer after executing (1230) the mobility operation.

8. The method of claim 7, wherein:the second security update is performed based on the second set of security information when the unprotected second message is received while the message timer is running; andthe method further comprises, when the unprotected second message is received after the message timer has expired, refraining from performing (1280) the second security update and entering a non-connected state with respect to the second RAN node.

9. The method of claim 7-8, further comprising performing (1250) one or more the following while the message timer is running and the unprotected second message has not been received:discarding (1251) a further message that includes at least part of the second set of security information, wherein the further message is protected by encryption and / or integrity protection; andrefraining from performing (1252) any security updates with respect to the second RAN node.

10. The method of any of claims 1-9, wherein the first set of security information is included in one or more of the following: the mobility configuration, and the first message.

11. The method of claim 10, wherein content of the first message is neither encrypted nor integrity-protected.

12. The method of any of claims 1-11, wherein the received mobility configuration is secured based on a first security key associated with the first RAN node, and the first securitykey is associated with the following: a first key identifier, and a first parameter from which a second security key may be derived.

13. The method of claim 12, wherein the first key identifier is a next hop chaining count, NCC, and the first parameter is a next hop, NH, parameter.

14. The method of any of claims 12-13, wherein:performing (1270) the first security update based on the first set of security information comprises deriving (1271) a second security key usable to secure communication with the second RAN node; andperforming (1270) the second security update based on the second set of security information comprises deriving (1272) a third security key usable to secure communication with the second RAN node.

15. The method of claim 14, wherein at least one of the second security key and the third security key is derived based on one or more of the following associated with the first mobility candidate cell: a physical cell identity, PCI; and a downlink, DL, carrier frequency.

16. The method of any of claims 1-15, wherein the first set of security information includes or indicates one or more of the following:a first security key associated with the first RAN node;a first key identifier associated with the first security key;a first parameter associated with the first security key;identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;to perform a security update in conjunction with the mobility operation;to perform a vertical key derivation in conjunction with the mobility operation;to perform a horizontal key derivation in conjunction with the mobility operation; to perform a further security update for the second RAN node after the mobility operation; one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed; andone or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

17. The method of any of claims 1-16, wherein the second set of security information includes or indicates one or more of the following:a second security key associated with the second RAN node;a second key identifier associated with the second security key;a second parameter from which a third security key may be derived;identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;to perform a security update;to perform a vertical key derivation;to perform a horizontal key derivation; andone or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

18. The method of any of claims 1-17, wherein one of the following applies:the first and second RAN nodes are different gNBs such that the mobility operation is inter-gNB; orthe first and second RAN nodes are different centralized units, CUs, such that the mobility operation is inter-CU.

19. A method for a first radio access network, RAN, node configured to provide a serving cell for user equipment, UEs, the method comprising:sending (1320), to a UE via the serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node; and sending (1330) to the UE a first message including a command to execute the mobility operation to a first one of the mobility candidate cells,wherein one or more of the following includes a first set of security information related to the second RAN node, which configures the UE to perform a first security update in conjunction with the mobility operation: the mobility configuration, and the first message.

20. The method of claim 19, wherein the first message is one of the following: a medium access control, MAC, control element, CE; downlink control information, DCI; or a radio resource control, RRC, message.

21. The method of claim 20, wherein one of the following applies:the mobility operation is a layer- l / layer-2 triggered intercell mobility, LTM, cell switch and the first message is an LTM cell switch MAC CE; orthe mobility operation is a layer-3 handover and the first message is an RRC handover command.

22. The method of any of claims 19-21, wherein content of the first message is neither encrypted nor integrity-protected.

23. The method of any of claims 19-22, wherein the mobility configuration is secured based on a first security key associated with the first RAN node, and the first security key is associated with the following: a first key identifier, and a first parameter from which a second security key may be derived.

24. The method of claim 23, wherein the first key identifier is a next hop chaining count, NCC, and the first parameter is a next hop, NH, parameter.

25. The method of any of claims 19-24, further comprising receiving (1310) the one or more mobility candidate configurations from the second RAN node.

26. The method of any of claims 19-25, further comprising, after sending (1330) the first message, sending (1340) to the second RAN node a notification of the mobility operation by the UE.

27. The method of any of claims 19-26, wherein the first set of security information includes or indicates one or more of the following:a first security key associated with the first RAN node;a first key identifier associated with the first security key;a first parameter associated with the first security key;identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;to perform a security update in conjunction with the mobility operation;to perform a vertical key derivation in conjunction with the mobility operation;to perform a horizontal key derivation in conjunction with the mobility operation; to perform a further security update for the second RAN node after the mobility operation;one or more identifiers associated with the first RAN node, which are usable to determine whether a security key update is needed; andone or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

28. The method of any of claims 19-27, wherein one of the following applies:the first and second RAN nodes are different gNBs such that the mobility operation is inter-gNB; orthe first and second RAN nodes are different centralized units, CUs, such that the mobility operation is inter-CU.

29. A method for a second radio access network, RAN, node configured to provide one or more mobility candidate cells for a user equipment, UE, the method comprising:determining (1420) that the UE has executed a mobility operation from a serving cell provided by a first RAN node to a first one of the mobility candidate cells provided by the second RAN node; andsubsequently sending (1430) to the UE a second message including the following: a second set of security information, and a command to perform a second security update based on the second set of security information.

30. The method of claim 29, further comprising sending (1410), to the first RAN node, one or more mobility candidate configurations for the mobility operation to the respective one or mobility candidate cells, wherein the mobility operation is based on a first one of the mobility candidate configurations associated with the first mobility candidate cell.

31. The method of any of claims 29-30, wherein the mobility operation is one of the following: alayer-l / layer-2 triggered intercell mobility, LTM, cell switch, or s a layer-3 handover.

32. The method of any of claims 29-31, wherein the second message is one of the following: a medium access control, MAC, control element, CE; downlink control information, DCI; or a radio resource control, RRC, message.

33. The method of any of claims 29-32, wherein the second message is unprotected by either encryption or integrity protection.

34. The method of any of claims 29-33, wherein determining (1420) that the UE has executed the mobility operation is based on receiving (1421) one or more of the following: a notification from the first RAN node, a notification from a distributed unit, DU, of the second RAN node; or a message from the UE via the first mobility candidate cell.

35. The method of any of claims 29-34, wherein the second set of security information includes or indicates one or more of the following:a second security key associated with the second RAN node;a second key identifier associated with the second security key;a second parameter from which a third security key may be derived;identifiers of one or more security algorithms usable to calculate security keys for use with the second RAN node;to perform a security update;to perform a vertical key derivation;to perform a horizontal key derivation; andone or more identifiers associated with the second RAN node, which are usable to determine whether a security key update is needed.

36. The method of any of claims 29-35, wherein one of the following applies:the first and second RAN nodes are different gNBs such that the mobility operation is inter-gNB; orthe first and second RAN nodes are different centralized units, CUs, such that the mobility operation is inter-CU.

37. User equipment, UE (310, 510, 1512, 1612, 1700) configured for mobility between cells of a radio access network, RAN (199, 1504, 1600), the UE comprising communication interface circuitry (1712) and processing circuitry (1702) that are operatively coupled and are configured to:receive, from a first RAN node (100, 320, 520, 1510, 1610, 1800, 1902) via a serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node (150, 320, 530, 1510, 1610, 1800, 1902);receive from the first RAN node a first message including a command to execute the mobility operation to a first one of the mobility candidate cells; and execute the mobility operation from the serving cell to the first mobility candidate cell;andperform one or more of the following in conjunction with or after the mobility operation:a first security update based on a first set of security information related to the second RAN node, obtained before executing the mobility operation; and a second security update based on a second set of security information related to the second RAN node, obtained after executing the mobility operation.

38. The UE of claim 37, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the methods of any of claims 2-18.

39. User equipment, UE (310, 510, 1512, 1612, 1700) configured for mobility between cells of a radio access network, RAN (199, 1504, 1600), the UE being further configured to:receive, from a first RAN node (100, 320, 520, 1510, 1610, 1800, 1902) via a serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node (150, 320, 530, 1510, 1610, 1800, 1902);receive from the first RAN node a first message including a command to execute the mobility operation to a first one of the mobility candidate cells; and execute the mobility operation from the serving cell to the first mobility candidate cell;andperform one or more of the following in conjunction with or after the mobility operation:a first security update based on a first set of security information related to the second RAN node, obtained before executing the mobility operation; and a second security update based on a second set of security information related to the second RAN node, obtained after executing the mobility operation.

40. The UE of claim 39, being further configured to perform operations corresponding to the methods of any of claims 2-18.

41. Non-transitory, computer-readable medium (1710) storing computer-executable instructions that, when executed by processing circuitry (1702), cause the method of any of claims 1-18 to be performed by the UE (310, 510, 1512, 1612, 1700) configured for mobility between cells of the RAN (199, 1504, 1600).

42. Computer program product (1714) comprising computer-executable instructions that, when executed by processing circuitry (1702), cause the method of any of claims 1-18 to be performed by the UE (310, 510, 1512, 1612, 1700) configured for mobility between cells of the RAN (199, 1504, 1600).

43. First radio access network, RAN, node (100, 320, 520, 1510, 1610, 1800, 1902) configured to provide a serving cell for user equipment, UEs (310, 510, 1512, 1612, 1700), the first RAN node comprising communication interface circuitry (1806, 1904) and processing circuitry (1802, 1904) that are operatively coupled and are configured to:send, to a UE via the serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one or more mobility candidate cells provided by a second RAN node (150, 320, 530, 1510, 1610, 1800, 1902); andsend to the UE a first message including a command to execute the mobility operation to a first one of the mobility candidate cells,wherein one or more of the following includes a first set of security information related to the second RAN node, which configures the UE to perform a first security update in conjunction with the mobility operation: the mobility configuration, and the first message.

44. The first RAN node of claim 43, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the methods of any of claims 20-28.

45. First radio access network, RAN, node (100, 320, 520, 1510, 1610, 1800, 1902) configured to provide a serving cell for user equipment, UEs (310, 510, 1512, 1612, 1700), the first RAN node being further configured to:send, to a UE via the serving cell, a mobility configuration comprising one or more mobility candidate configurations for a mobility operation to respective one ormore mobility candidate cells provided by a second RAN node (150, 320, 530, 1510, 1610, 1800, 1902); andsend to the UE a first message including a command to execute the mobility operation to a first one of the mobility candidate cells,wherein one or more of the following includes a first set of security information related to the second RAN node, which configures the UE to perform a first security update in conjunction with the mobility operation: the mobility configuration, and the first message.

46. The first RAN node of claim 45, being further configured to perform operations corresponding to the methods of any of claims 20-28.

47. Non-transitory, computer-readable medium (1804, 1904) storing computer-executable instructions that, when executed by processing circuitry (1806, 1904), cause the method of any of claims 19-28 to be performed by the first RAN node (100, 320, 520, 1510, 1610, 1800, 1902) configured to provide the serving cell for UEs (310, 510, 1512, 1612, 1700).

48. Computer program product (1804a, 1904a) comprising computer-executable instructions that, when executed by processing circuitry (1806, 1904), cause the method of any of claims 19-28 to be performed by the first RAN node (100, 320, 520, 1510, 1610, 1800, 1902) configured to provide the serving cell for UEs (310, 510, 1512, 1612, 1700)..

49. Second radio access network, RAN, node (150, 320, 530, 1510, 1610, 1800, 1902) configured to provide one or more mobility candidate cells user equipment, UEs (310, 510, 1512, 1612, 1700), the second RAN node comprising communication interface circuitry (1806, 1904) and processing circuitry (1802, 1904) that are operatively coupled and are configured to:determine that the UE has executed a mobility operation from a serving cell provided by a first RAN node (100, 320, 520, 1510, 1610, 1800, 1902) to afirst one ofthe mobility candidate cells provided by the second RAN node; and subsequently send to the UE a second message including the following: a second set of security information, and a command to perform a second security update based on the second set of security information.

50. The second RAN node of claim 49, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to the methods of any of claims 30-36.

51. Second radio access network, RAN, node (150, 320, 530, 1510, 1610, 1800, 1902) configured to provide one or more mobility candidate cells user equipment, UEs (310, 510, 1512, 1612, 1700), the second RAN node being further configured to:determine that the UE has executed a mobility operation from a serving cell provided by a first RAN node (100, 320, 520, 1510, 1610, 1800, 1902) to afirst one ofthe mobility candidate cells provided by the second RAN node; and subsequently send to the UE a second message including the following: a second set of security information, and a command to perform a second security update based on the second set of security information.

52. The second RAN node of claim 51, being further configured to perform operations corresponding to the methods of any of claims 30-36.

53. Non-transitory, computer-readable medium (1804, 1904) storing computer-executable instructions that, when executed by processing circuitry (1806, 1904), cause the method of any of claims 29-36 to be performed by the second RAN node (150, 320, 530, 1510, 1610, 1800, 1902) configured to provide the one or more mobility candidate cells for UEs (310, 510, 1512, 1612, 1700).

54. Computer program product (1804a, 1904a) comprising computer-executable instructions that, when executed by processing circuitry (1806, 1904), cause the method of any of claims 29-36 to be performed by the second RAN node (150, 320, 530, 1510, 1610, 1800, 1902) configured to provide the one or more mobility candidate cells for UEs (310, 510, 1512, 1612,

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