Mobility procedures

Abstract

The embodiment of the invention provides a method and device for mobility procedures and a computer readable medium. In accordance with an example aspect of the present disclosure, there is provided an apparatus configured to: determine a radio link failure with a group of primary cells when operating in dual connectivity, where a selective activation (SAPC) configuration of primary-secondary cell change is stored for a set of secondary cells; determining a new secondary node encryption key based at least in part on a primary node key received from the primary node during a connection reestablishment of a connection with the primary node after a radio link failure with a primary cell group including the primary node has occurred; and after the radio link failure, identifying the secondary cell using the SAPC configuration stored prior to the radio link failure, and connecting to the identified secondary cell based at least in part on the new secondary node encryption key.

Description

Technical Field

[0001] The present disclosure relates to mobility procedures in a cellular communication network. Background Art

[0002] In a cellular communication network, user devices attach themselves to cells to access network services such as connectivity, positioning and telephony. When user devices roam within the coverage area of ​​the network, they change attachment between cells to maintain a viable communication path with the network side.

[0003] In case of a radio link failure RLF with a base station of the network, the affected user equipment may take corrective measures such as requesting re-establishment of the radio link with the network. To mitigate the impact of RLF on the connection, user equipment may be provided with synchronized radio links with more than one base station or cell. Summary of the invention

[0004] According to some aspects, the subject matter of independent claims is provided. Some embodiments are defined in the dependent claims. The scope of protection sought by the various embodiments of the present invention is set forth by the independent claims. The embodiments, examples and features (if any) described in this specification that do not fall within the scope of the independent claims should be interpreted as examples that help understand the various embodiments of the present invention.

[0005] According to a first aspect of the present disclosure, a device is provided, comprising: at least one processing core; and at least one memory storing instructions, which, when executed by the at least one processing core, causes the device to at least: determine a radio link failure with a primary cell group when operating under dual connectivity, wherein a selective activation SAPC configuration for a primary-secondary cell change is stored for a set of secondary cells; determine a new secondary node encryption key based at least in part on a primary node key received from the primary node during connection reestablishment of a connection with the primary node after a radio link failure with a primary cell group including a primary node occurs; and identify a secondary cell using a SAPC configuration stored before the radio link failure, and connect to the identified secondary cell based at least in part on the new secondary node encryption key after a radio link failure with the primary cell group including a primary node.

[0006] According to a second aspect of the present disclosure, a device is provided, comprising: at least one processing core; and at least one memory storing instructions, which, when executed by the at least one processing core, causes the device to at least: when operating as a master node in a dual-connection session of a user equipment, provide a user equipment with a selective activation SAPC configuration for a master-secondary cell change for a set of secondary cells; after a radio link failure occurs, determine a new secondary node encryption key based at least in part on a master node key determined by the device as a response to receiving a connection reestablishment request or a reconfiguration completion message from the user equipment; and after the radio link failure, update the set of secondary cells using the new secondary node encryption key without providing a user equipment context to the set of secondary cells.

[0007] According to a third aspect of the present disclosure, a method is provided, comprising: when operating under dual connectivity, determining in a device a radio link failure with a primary cell group, wherein a selective activation SAPC configuration for a primary-secondary cell change is stored for a set of secondary cells; after a radio link failure with a primary cell group including a primary node occurs, during connection reestablishment of a connection with the primary node, determining a new secondary node encryption key based at least in part on a primary node key received from the primary node; and after the radio link failure, identifying the secondary cell using the SAPC configuration stored before the radio link failure, and connecting to the identified secondary cell based at least in part on the new secondary node encryption key.

[0008] According to a fourth aspect of the present disclosure, a method is provided, comprising: when operating as a master node in a dual-connection session of a user equipment, providing, by a device, to the user equipment, a selective activation SAPC configuration for a master-secondary cell change for a set of secondary cells; after a radio link failure occurs, determining, at least in part based on a master node key determined by the device, a new secondary node encryption key as a response to receiving a connection reestablishment request or a reconfiguration completion message from the user equipment; and after the radio link failure, updating the set of secondary cells using the new secondary node encryption key without providing a user equipment context to the set of secondary cells.

[0009] According to a fifth aspect of the present disclosure, a device is provided, comprising components for: when operating under dual connectivity, determining in the device a radio link failure with a primary cell group, wherein a selective activation SAPC configuration for a primary-secondary cell change is stored for a set of secondary cells; after a radio link failure with a primary cell group including a primary node occurs, during connection reestablishment of a connection with the primary node, determining a new secondary node encryption key based at least in part on a primary node key received from the primary node; and after the radio link failure, identifying the secondary cell using the SAPC configuration stored before the radio link failure, and connecting to the identified secondary cell based at least in part on the new secondary node encryption key.

[0010] According to a sixth aspect of the present disclosure, a device is provided, comprising components for: when operating as a primary node in a dual-connection session of a user equipment, providing a selective activation SAPC configuration for a primary-secondary cell change for a set of secondary cells to the user equipment; after a radio link failure occurs, determining a new secondary node encryption key based at least in part on a primary node key determined by the device as a response to receiving a connection reestablishment request or a reconfiguration completion message from the user equipment; and after the radio link failure, updating the set of secondary cells using the new secondary node encryption key without providing a user equipment context to the set of secondary cells.

[0011] According to the seventh aspect of the present disclosure, a device is provided, comprising: at least one processing core; and at least one memory, wherein the at least one memory stores instructions, which, when executed by the at least one processing core, causes the device to at least: receive a secondary node encryption key and a context of a user device from a node acting as a primary node in a dual-connection session of a user device as part of a selective activation SAPC setting for a primary-secondary cell change; receive a new secondary node encryption key from the node acting as the primary node so that the context of the user device is not updated; and after receiving the new secondary node encryption key, receive a connection request based on the SAPC setting from the user device.

[0012] According to an eighth aspect of the present disclosure, a non-transitory computer-readable medium is provided, having a set of computer-readable instructions stored thereon, which, when executed by at least one processor, causes the device to at least: when operating under dual connectivity, determine a radio link failure with a primary cell group, wherein a selective activation SAPC configuration for a primary-secondary cell change is stored for a set of secondary cells; after a radio link failure with a primary cell group including a primary node occurs, during connection reestablishment of a connection with the primary node, determine a new secondary node encryption key based at least in part on a primary node key received from the primary node; and after a radio link failure, identify a secondary cell using a SAPC configuration stored before the radio link failure, and connect to the identified secondary cell based at least in part on the new secondary node encryption key.

[0013] According to the ninth aspect of the present disclosure, a non-transitory computer-readable medium is provided, having a set of computer-readable instructions stored thereon, which, when executed by at least one processor, causes the device to at least: when operating as a master node in a dual-connection session of a user device, provide a user device with a selective activation SAPC configuration for a master-secondary cell change for a set of secondary cells; after a radio link failure occurs, determine a new secondary node encryption key based at least in part on a master node key determined by the device as a response to receiving a connection reestablishment request or a reconfiguration completion message from the user device; and after the radio link failure, update the set of secondary cells using the new secondary node encryption key without providing a user equipment context to the set of secondary cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 illustrates example systems in accordance with at least some embodiments of the present invention;

[0015] Figure 2 illustrates example signaling flows according to at least some embodiments of the present invention;

[0016] Figure 3 illustrates example signaling flows according to at least some embodiments of the present invention;

[0017] Figure 4 illustrates an example apparatus capable of supporting at least some embodiments of the present invention, and

[0018] Figure 5 is a flow chart of a method according to at least some embodiments of the present invention. DETAILED DESCRIPTION

[0019] This document describes a method for reducing delays caused by radio link failures RLF of cells in a primary cell group in a cellular system. Specifically, the selective activation SAPC configuration of the primary and secondary cell change in the user equipment UE is maintained on the RLF, and the UE context in the secondary cell prepared for the UE is also maintained, thereby eliminating the need to provide the SAPC configuration and UE context to the UE and the prepared secondary cell respectively again. After the RLF, the primary node in the primary cell group only uses the new encryption key information to update the UE and the prepared secondary node in the form of a new secondary node key for the secondary node and a new primary node key for the UE.

[0020] Figure 1 An example system according to at least some embodiments of the present invention is illustrated. The system includes base stations 130, 135 communicating with a UE, such as UE 110. A radio link connects the base station 130 and the UE 110. The radio link may be bidirectional, including an uplink UL for transmitting information from the UE 110 to the base station 130, and a downlink DL for transmitting information from the base station 130 to the UE 110. The base station 130 may be a primary node in a dual connectivity session of the UE 110, while the base station 135 is a secondary node. By dual connectivity, a session in which the UE utilizes radio resources of multiple carriers to improve the UE throughput is meant.

[0021] Dual connectivity DC is an operating mode in which a UE with multiple receive and transmit capabilities in a radio resource control RRC connected state can be configured to use radio resources of two different schedulers located in two base stations, namely a main base station (referred to as a main node MN) and a secondary base station (referred to as a secondary node SN). MN and SN can be connected to each other via a backhaul connection, such as an inter-base station interface, as an example, such as the X2 interface in the Third Generation Partnership Project 3GPP system. In other words, DC allows the UE to simultaneously send and receive data on multiple component carriers from two cell groups via MN and SN. MN is included in the main cell group MCG, and SN is included in the secondary cell group SCG.

[0022] Base stations 130 and 135 are also communicatively coupled to a core network node 140, which may include, for example, a mobility management entity MME, or an access and mobility management function AMF. Core network node 140 may be coupled to additional core network nodes, and to a network 150, which may include, for example, the Internet or an enterprise network. The system may communicate with additional networks via network 150. For clarity, Figure 1 Examples of additional core network nodes not shown in FIG. 1 include a gateway and a subscriber information repository.

[0023] The base station 130 has multiple cells 130A and 130B, in which the UE 110 is located. Figure 1 In the illustrated case, the base station 135 is connected to the cell 130A, and the base station 135 has multiple cells 135A and 135B. The number of cells may exceed Figure 1 Mobility events may include switching from one cell or beam to another cell or beam of the same base station, or switching from one base station to another base station. To support the mobility procedures, the UE is configured to make measurements to measure the signal strength of neighboring beams and / or cells and report the results of these measurements to the network. The network may then make decisions about mobility events (such as beam changes or cell switching) based at least in part on the reported measurement results.

[0024] Such mobility measurements on the UE side may include layer 3 measurements, and the corresponding reports are layer 3 reports or L3 reports. Similarly, the handover command from the network is usually a layer 3 message. Layer 3 is the radio resource control RRC layer in the technology standardized by the third generation partnership project 3GPP. In 3GPP technology, layer 1 or L1 in the lower layer is the physical layer, and layer 2 or L2 includes the medium access control MAC, the radio link control RLC, and the packet data convergence protocol PDCP protocol.

[0025] When the mobility measurement results indicate that the signal strength of the cell or beam to which the UE is currently attached is decreasing and the signal strength of another cell or beam is increasing, the network may command switching to another cell or beam based at least in part on the mobility measurement report from the UE.

[0026] The selective activation SAPC configuration of the primary and secondary cell change can be provided by the MN to the UE. The SAPC configuration may include conditions related to the selection of a new secondary cell (such as a primary and secondary cell PSCell, for example). More specifically, the SAPC configuration may include conditions specific to the candidate secondary cell, which define the situation in which the UE should initiate a process for changing the primary and secondary cell to the candidate secondary cell. The UE can evaluate these conditions to conditionally initiate a change in the primary and secondary cell. The primary and secondary cell is a cell in the secondary cell group, and the UE initiates a connection to the primary and secondary cell within the secondary cell group. Similarly, the UE exchanges more signaling with the primary and secondary cells than with other secondary cells. For example, the SAPC conditions included in the SAPC configuration may include conditions related to the reference signal received power RSRP from the secondary cell, conditions related to the current location of the UE, and conditions related to the buffer state of the UE. For example, the SAPC configuration may define that all SAPC conditions of the configuration must be met at the same time before the configuration can trigger the UE to start the primary and secondary cell change.

[0027] In principle, in the event of an RLF with a cell in the primary cell group, particularly if the RLF involves a MN, the UE may discard the SAPC configuration it received from the MN due to at least temporary loss of connection to the node. However, it is surprisingly found that since the UE will remain in the physical neighborhood of the MN and the (multiple) secondary cells to which the (multiple) SAPC configurations are related, the SAPC configurations can be retained for possible use after the RLF or even during the RLF, as will be described in detail herein. Similarly, the SN prepared to receive the UE can retain these contexts through the RLF of the UE with the MN, rather than abandoning the UE context of the user equipment. The MN can send new SN encryption keys to the prepared SN to update its preparations for receiving the UE, and the MN can also send new primary node keys (MN keys) to the UE after the RLF to update the SAPC configurations, which otherwise might be used as those stored in the UE before the RLF.

[0028] Prior to RLF, the UE may indicate to the MN that it has the capability to retain the SAPC configuration through RLF with the MN, and if RLF occurs between the UE and the MN, the MN may responsively instruct the UE to use this capability and retain the SAPC configuration. Once the MN has so configured the UE, the MN may also cause the SN to retain the UE context, rather than discarding it, in the event of an RLF between the UE and the MN or another primary cell group node. If the SN discards the UE context, it may need to be re-provided from the MN, thereby unnecessarily increasing the signaling load in the network.

[0029] The UE context includes information about the UE's active protocol connections, such as information identifying the communicating counterpart and packet counter values, which are necessary to provide seamless or smoother cell changes. In addition to information about the UE's active protocol connections, the UE context may also store UE state information, security information, and UE capability information.

[0030] Figure 2 An example signaling flow according to at least some embodiments of the present invention is illustrated. A UE, a MN and at least one secondary node, for example, two secondary nodes SN1 and SN2 are arranged in sequence from left to right on the vertical axis. Time progresses from top to bottom.

[0031] In phase 210, the MN prepares for SAPC of SN1 and SN2 with the UE by, for example, providing these nodes with the UE context and the SN encryption key. With this information, these nodes are ready to initiate communications with the UE, thereby making these communications protected and encrypted over the air interface using the SN encryption key. SN The key generator may be used to generate the key. The input of the key generator may include, for example, the MN key (e.g., KgNB ), SN counter and SN counter length. To run the key generator, the UE extracts the next counter value from the SN counter list. The SN counter list can be provided to the UE by the MN, for example, when the MN configures the UE to establish a link with the SN. Once the SN counter list is provided to the UE, the UE will also know the SN counter length because the counter is explicit. Therefore, the UE will know all three inputs required for SN key generation: MN key, SN counter and SN counter length. When the UE is prepared for multiple candidate SNs, the UE can provide a separate counter list for each candidate SN. If the UE switches to a new PSCell, it can extract a new value from the counter list of the target cell to generate a suitable SN key. For example, the SN counter information can be provided to the UE from the MN in an RRC reconfiguration or RRC reconstruction message.

[0032] The serving SN may need to know the SN key that the UE will use for end-to-end encryption. Since the MN determines the UE's SN counter value, the MN already knows the key that the UE will use using the SN counter. The MN can use the appropriate counter value to calculate the SN key and send the SN key to be used to the SN before the SN becomes the serving SN (e.g., when the SN is added or changed). In either case (SN addition, or SN change), the MN can share the SN key K with the candidate SN during preparation (e.g., via an SN addition request message). SN If there are multiple PSCell preparations requested in one SN Add Request message, all prepared PSCells will share the same K SN .

[0033] Additionally, the MN may configure the UE to retain the SAPC configuration via RLF with the MN, either before or after stage 210. In order for the MN to so instruct the UE, the UE may first provide the MN with an indication that the UE has this capability, as described herein above.

[0034] In stage 220, the UE is in dual connectivity with the MN and SN1. The UE may be configured with SAPC for SN1 and SN2. Stage 230 represents RLF with the MN. RLF may be caused by a sudden deterioration of radio conditions (e.g., due to an interference spike). The UE responds to the RLF of stage 230 by starting cell reselection in stage 240. The SAPC configuration provided before the RLF of stage 230 is retained in the UE and is not discarded or deleted. In some embodiments, the UE begins evaluating the SAPC condition of the retained SAPC configuration in stage 240.

[0035] In stage 250, the UE sends an RRC re-establishment request to the MN. The MN may detect or determine RLF based on the received RRC re-establishment request. Optionally, the message includes a primary and secondary cell PSCell identifier selected based on the evaluation of the SAPC condition in stage 240. If the SAPC condition for any SN (SN1 or SN2) is met before sending the RRC re-establishment request, the UE may indicate this to the MN through the cell that meets this condition. The SAPC condition may be referred to as a conditional PSCell change CPC condition. For example, an identifier of a node or cell that meets the condition may be included in the RRC re-establishment request. Including the primary and secondary cell identifiers in this message saves process time and enables the UE to benefit greatly from retaining the SAPC configuration on the RLF.

[0036] Phase 260 comprises the UE evaluating the SAPC condition, for example if the primary and secondary cell identifiers have not been included in the RRC message of phase 250, or if the evaluation has not been initiated in phase 240. If the primary and secondary cell identifiers have already been sent to the MN in phase 250, phase 260 may be skipped.

[0037] In stage 270, the MN determines or generates or calculates a new SN encryption key as a response to the RRC reestablishment request of stage 250, and, in stages 280 and 290, this new SN encryption key is provided to SN1 and SN2, as illustrated in the figure. Optionally, SN1 and SN2 may confirm receipt of the new SN encryption key. Thus, SN1 and SN2 have the UE context that was already stored before RLF 230, and the new SN encryption key provided to them in stages 280 and 290. The MN learns about the prepared SN through the UE context. The MN may generate the key using the key generator described above.

[0038] In stage 2100, the MN provides an RRC reestablishment response to the UE as a response to the RRC reestablishment request of stage 250. The response of stage 2100 includes MN RRC reconfiguration. The message of stage 2100 includes a new master node encryption key. The message of stage 2100 may include instructions for the UE to maintain an SN counter list. In the example, the MN will send a new SN counter list to be used in key generation for the target cell. Optionally, if the UE provides the MN with an identifier of the selected PSCell that previously met the SAPC condition in the RRC reestablishment request of stage 250, the MN may directly configure a dual connection with the selected PSCell in stage 2100. As stage 2110, the UE responds by sending an RRC reestablishment complete message to the MN, and in stage 2120, the MN provides an RRC reestablishment complete message to SN1 including the selected PSCell.

[0039] In stage 2130, the UE identifies the PSCell to connect to by evaluating the SAPC condition, unless this has been done previously. The UE generates or calculates a new SN encryption key based on the master node encryption key received in stage 2100 and using the SN counter information maintained in the UE before the RLF of stage 230. The UE may generate the key using the key generator described above. In stage 2140, the UE performs a random access procedure with SN1 to establish the SN segment of the DC session. In stage 2150, the MN may transmit the SN status to SN1.

[0040] Compared with the case where the SAPC configuration in the UE is discarded, Figure 2 The process in saves time because evaluating the SAPC condition can occur earlier in stages 240, 260 or 2130 than would be possible if the MN had to prepare the SN in advance for SAPC and provide the SAPC configuration to the UE again after RRC connection reestablishment.

[0041] Figure 3 Example signaling flows in accordance with at least some embodiments of the present invention are illustrated. Figure 3 The process and Figure 2 is similar, and the vertical axis corresponds to Figure 2 The same node in . Figure 3 The process is to conditionally switch CHO recovery. This process is the same as the above Figure 2 The procedure described for RRC Reestablishment is similar, except that RRC reconfiguration (as specified in CHO recovery) is used instead of RRC reconstruction.

[0042] In addition, before or after stage 310, the MN may configure the UE to retain the SAPC configuration through RLF with the MN. In order for the MN to so instruct the UE, the UE may first provide the MN with an indication that the UE has this capability, as described above herein. Stages 310, 320, 330, 340, and 360 correspond to stages 210, 220, 230, 240, and 260.

[0043] Phase 350 includes the transmission of RRC reconfiguration complete from the UE to the MN. The MN may detect or determine RLF based on the received RRC reconfiguration complete message. Optionally, if a conditional PSCell change condition (i.e., (multiple) SAPC conditions) has been met for any SN at this stage, the UE notifies the MN. If the SAPC condition is met before the RRC reconfiguration complete message is sent, the UE may indicate this to the MN using the cell that meets the condition. For example, an identifier of a node or cell that meets the condition may be included in the RRC reconfiguration complete message.

[0044] Phase 370 corresponds to phase 270, in which the MN determines a new SN encryption key and provides it to the SN in phases 380 and 390. Figure 2 In the case of , the SN may optionally confirm receipt of the new SN encryption key. Now, the SN has the new SN encryption key and the UE context that has been stored before the RLF in phase 330. The MN learns the prepared SN through the UE context.

[0045] In stage 3100, the MN provides an RRC reconfiguration message containing the MN RRC reconfiguration to the UE. The message includes a new MN encryption key. If the identifier of the PSCell that meets the SAPC condition is provided to the MN in stage 350, the message of stage 3100 may also include instructions for starting a DC session, where the MN acts as the master node and the cell identified in stage 350 acts as the PSCell. The message of stage 3100 may include instructions for the UE to maintain an SN counter list. In the example, the MN will send a new SN count list to be used in key generation for the target cell. The UE responds to the message of stage 3100 by sending an RRC reconstruction completion message to the MN in stage 3110. In stage 3120, the MN forwards the RRC reconstruction completion message to SN1, which includes the identified PSCell.

[0046] In stage 3130, the UE identifies the PSCell to connect to by evaluating the SAPC condition, unless this has been done previously. The UE generates or calculates a new SN encryption key based on the master node encryption key received in stage 3100 and using the SN counter information maintained in the UE before the RLF of stage 330. In stage 3140, the UE performs a random access procedure with SN1 to establish the SN segment of the DC session. In stage 3150, the MN may transmit the SN status to SN1.

[0047] like Figure 2 The situation during the process, Figure 3 The process also saves time compared to the case where the SAPC configuration in the UE is discarded, because evaluating the SAPC condition can occur earlier in stages 340, 360 or 3130 than the possible time when the MN must prepare the SN in advance for SAPC and provide the SAPC configuration to the UE again after the RRC connection is reestablished.

[0048] Figure 4An example device capable of supporting at least some embodiments of the present invention is illustrated. Illustrated is a device 400, which may include, for example, a mobile communication device (such as a UE) or include a base station in an applicable component. Included in the device 400 is a processor 410, which may include, for example, a single-core or multi-core processor, wherein the single-core processor includes one processing core, and the multi-core processor includes more than one processing core. Processor 410 may generally include a control device. Processor 410 may include more than one processor. When processor 410 includes more than one processor, device 400 may be a distributed device, wherein the processing of tasks occurs in more than one physical unit. Processor 410 may be a control device. For example, the processing core may include a Cortex-A8 processing core manufactured by ARM Holdings or a Zen processing core designed by Advanced Micro Devices Corporation. The processing core or processor may be, or may include, at least one qubit. Processor 410 may include at least one Qualcomm Snapdragon and / or Intel Atom processor. Processor 410 may include at least one application-specific integrated circuit ASIC. Processor 410 may include at least one field programmable gate array FPGA. Optionally, processor 410, along with memory and computer instructions, may be means for performing method steps (such as determining, identifying, receiving, sending, initiating, updating, and providing) in device 400. Processor 410 may be configured, at least in part, by computer instructions to perform actions.

[0049] The processor may include a circuit system, or be configured as a circuit system or multiple circuit systems, which are configured to perform various stages of the method according to the embodiments described herein. As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) a hardware circuit implementation only, such as an implementation in analog and / or digital circuit systems only; and (b) a combination of hardware circuits and software, such as (as applicable): (i) a combination of (multiple) analog and / or digital hardware circuits and software / firmware, and (ii) (multiple) hardware processors and software (including (multiple) digital signal processors), software and any part of memory, which work together to enable the device (such as a UE or base station) to perform various functions; and (c) (multiple) hardware circuits and / or (multiple) processors that require software (e.g., firmware) to operate, such as (multiple) microprocessors, or a portion of (multiple) microprocessors, but the software may not be present when the software is not required for operation.

[0050] This definition of circuitry applies to all uses of the term in this application, including in any claims. By way of further example, as used in this application, the term circuitry also encompasses an implementation of only a hardware circuit or processor (or processors), or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example, and if applicable to a particular claim element, the term circuitry also encompasses a baseband integrated circuit or processor integrated circuit of a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0051] Device 400 may include memory 420. Memory 420 may include random access memory and / or permanent memory. Memory 420 may include at least one RAM chip. Memory 420 may be a computer-readable medium. For example, memory 420 may include solid-state, magnetic, optical and / or holographic memory. At least a portion of memory 420 is accessible to processor 410. Memory 420 may be at least partially included in processor 410. Memory 420 may be a component for storing information. Memory 420 may include computer instructions that processor 410 is configured to execute. When computer instructions configured to cause processor 410 to perform a specific action are stored in memory 420 and device 400 as a whole is configured to run under the guidance of processor 410 using computer instructions from memory 420, processor 410 and / or at least one of its processing cores may be considered to be configured to perform the specific action. Memory 420 may be at least partially located outside device 400, but may be accessed by device 400. Memory 420 may be transient or non-transient. As used herein, the term "non-transitory" is a restriction on the medium itself (ie, tangible, not a signal), not on the persistence of data storage (eg, RAM vs. ROM).

[0052] The device 400 may include a transmitter 430. The device 400 may include a receiver 440. The transmitter 430 and the receiver 440 may be configured to transmit and receive information, respectively, according to at least one cellular or non-cellular standard. The transmitter 430 may include more than one transmitter. The receiver 440 may include more than one receiver. For example, the transmitter 430 and / or the receiver 440 may be configured to operate according to the Global System for Mobile Communications GSM, Wideband Code Division Multiple Access WCDMA, 5G, Long Term Evolution LTE, IS-95, Wireless Local Area Network WLAN, Ethernet, and / or Worldwide Interoperability for Microwave Access WiMAX standards.

[0053] The device 400 may include a near field communication NFC transceiver 450. The NFC transceiver 450 may support at least one NFC technology, such as NFC, Bluetooth, Wibree, or similar technology.

[0054] Device 400 may include a user interface UI 460. UI 460 may include at least one of a display, a keyboard, a touch screen, a vibrator (arranged to signal a user by vibrating device 400), a speaker, or a microphone. The user is able to operate device 400 via UI 460, such as accepting an incoming call, making a phone or video call, browsing the Internet, managing digital files stored in memory 420 or on a cloud accessible via transmitter 430 and receiver 440 or via NFC transceiver 450, and / or playing games.

[0055] Device 400 may include or be arranged to accept a subscriber identification module 470. Subscriber identification module 470 may include, for example, a subscriber identification module SIM card installable in device 400. Subscriber identification module 470 may include information identifying a subscription of a user of device 400. Subscriber identification module 470 may include encryption information that may be used to verify the identity of a user of device 400, and / or facilitate encryption of communication information, and billing of communications by the user of device 400 via device 400.

[0056] The processor 410 may be equipped with a transmitter, arranged to output information from the processor 410 to other devices included in the device 400 via wires inside the device 400. Such a transmitter may include a serial bus transmitter, for example, arranged to output information to the memory 420 via at least one wire for storage therein. Instead of a serial bus, the transmitter may include a parallel bus transmitter. Similarly, the processor 410 may include a receiver, which is arranged to receive information from other devices included in the device 400 in the processor 410 via wires inside the device 400. Such a receiver may include a serial bus receiver, for example, the receiver is arranged to receive information from the receiver 440 via at least one wire for processing in the processor 410. Instead of a serial bus, the receiver may include a parallel bus receiver.

[0057] The device 400 may include Figure 4 Other devices not shown in the figure. For example, when the device 400 includes a smartphone, it may include at least one digital camera. Some devices 400 may include a rear camera and a front camera, wherein the rear camera may be intended for digital photography and the front camera is used for video calling. The device 400 may include a fingerprint sensor that is arranged to at least partially authenticate a user of the device 400. In some embodiments, the device 400 lacks at least one of the above devices. For example, some devices 400 may lack an NFC transceiver 450 and / or a user identification module 470.

[0058] The processor 410, the memory 420, the transmitter 430, the receiver 440, the NFC transceiver 450, the UI 460 and / or the user identification module 470 may be interconnected in a variety of different ways via wires inside the device 400. For example, each of the above devices may be connected to a main bus inside the device 400, respectively, to allow the devices to exchange information. However, as will be appreciated by the skilled person, this is only an example, and depending on the embodiment, a variety of ways of interconnecting at least two of the above devices may be selected without departing from the scope of the present invention.

[0059] Figure 5 is a flow chart of a method according to at least some embodiments of the present invention. The various stages of the illustrated method may be performed in a user device or a control device, the control device being configured to control the functions of the user device when installed in the user device.

[0060] Stage 510 includes: when operating under dual connectivity, determining in the device a radio link failure with a primary cell group, wherein a selective activation SAPC configuration for a primary and secondary cell change is stored for a set of secondary cells. Stage 520 includes: after a radio link failure with the primary cell group occurs, during a connection reestablishment of a connection with a primary node, determining a new secondary node encryption key based at least in part on a primary node key received from the primary node. Finally, stage 530 includes: after a radio link failure, identifying a specific secondary cell using a SAPC configuration stored before the radio link failure, and connecting to the specific secondary cell based at least in part on the new secondary node encryption key.

[0061] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, process steps or materials disclosed herein, but are extended to equivalents recognized by ordinary technicians in the relevant technical field. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and are not intended to be limiting.

[0062] Throughout this specification, reference to an embodiment or a specific embodiment means that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. Thus, throughout this specification, the appearance of the phrase "in one embodiment" or "in an embodiment" does not necessarily refer to the same embodiment. For example, when a value is referred to using terms such as approximately or substantially, the exact value is also disclosed.

[0063] As used herein, for convenience, multiple items, structural elements, constituent elements, and / or materials can be presented in a general list. However, these lists should be understood as each member in the list is individually identified as an independent and unique member. Therefore, in the absence of contrary instructions, any individual member in such a list should not be interpreted as the de facto equivalent of any other member in the same list simply by virtue of its presentation in a common group. In addition, various embodiments and examples of the present invention and alternatives to its various components are mentioned herein. It is understandable that these embodiments, examples and alternatives should not be understood as de facto equivalents to each other, but should be regarded as independent and autonomous expressions of the present invention.

[0064] In addition, the features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the foregoing description, many specific details are provided, such as examples of length, width, shape, etc., to provide a thorough understanding of embodiments of the present invention. However, those skilled in the relevant art will recognize that the present invention can be practiced without one or more specific details, or practiced using other methods, components, materials, etc. In other cases, in order to avoid covering up various aspects of the present invention, well-known structures, materials, or operations are not shown or described in detail.

[0065] Although the above examples illustrate the principles of the present invention in one or more specific applications, it is obvious to those skilled in the art that a large number of modifications can be made in form, use and implementation details without inventiveness and without departing from the principles and concepts of the present invention. Therefore, the present invention is not intended to be limited except as set forth below.

[0066] The verbs "comprise" and "include" used in this document are open limitations that neither exclude nor require the presence of unrecited features. Unless explicitly stated otherwise, the features recited in the dependent claims may be freely combined with each other. Furthermore, it should be understood that the use of "a" or "an" (i.e. the singular form) throughout this document does not exclude the plural form.

[0067] As used herein, “at least one of the following: ” and “at least one of ,” and similar expressions (wherein a list of two or more elements is connected with “and” or “or”) refer to at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0068] Industrial Applications

[0069] At least some embodiments of the present invention find industrial application in cellular networks.

[0070] Glossary

[0071] 3GPP Third Generation Partnership Project

[0072] DC Dual Connection

[0073] MN Master Node

[0074] RRC Radio Resource Control

[0075] Selective activation of SAPC primary and secondary cell changes

[0076] SN Secondary Node

[0077] UE User Equipment

[0078] Reference numerals list

[0079]

Claims

1. A device for communication, comprising: at least one processing core; and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus to at least: - when operating in dual connectivity, determining a radio link failure with a primary cell group, wherein a selective activation SAPC configuration for primary to secondary cell change is stored for the set of secondary cells; - determining a new secondary node encryption key during connection re-establishment of a connection with the primary node after occurrence of the radio link failure with the primary cell group comprising the primary node, based at least in part on a primary node key received from the primary node, and - after the radio link failure, identifying a secondary cell using the SAPC configuration stored before the radio link failure, and connecting to the identified secondary cell based at least in part on the new secondary node encryption key. 2 . The apparatus according to claim 1 , further configured to receive an instruction from the network to maintain the SAPC configuration in the event of a radio link failure with a primary cell group.

3. The apparatus according to claim 1 or 2 is further configured to: send an indication to the network, indicating that: after the radio link failure with the primary cell group, the apparatus can use the SAPC configuration stored in the apparatus before the radio link failure with the primary cell group.

4. The apparatus according to any one of claims 1 to 3, wherein the apparatus is configured to start evaluating at least one condition included in the SAPC configuration after the radio link failure with the primary cell group and when one of the following occurs: Before sending a connection reestablishment request to the master node, or Before sending a reconfiguration completion message to the master node.

5. The apparatus according to claim 4, wherein the apparatus is configured to: identify the secondary cell based on the evaluation of the at least one condition, wherein the identified secondary cell satisfies the at least one condition, and the apparatus is further configured to: indicate the identified secondary cell to the primary node in the connection reestablishment request or in the reconfiguration completion message.

6. The apparatus according to claim 5, wherein the apparatus is configured to: A configuration for starting dual connectivity with the identified secondary cell is received.

7. An apparatus according to any preceding claim, configured to determine the new secondary node encryption key based at least in part on a secondary node SN counter list, and wherein the apparatus is configured to: receiving an instruction to maintain the SN counter list provided before the radio link failure; or The SN counter list to be used in key generation is received.

8. An apparatus for communication, comprising: at least one processing core; and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus to at least: - when operating as a primary node in a dual connectivity session of a user equipment, providing the user equipment with a selective activation SAPC configuration for a primary and secondary cell change for a set of secondary cells; - determining, after a radio link failure occurs, a new secondary node encryption key based at least in part on the primary node key determined by the apparatus as a response to receiving a connection reestablishment request or a reconfiguration complete message from the user equipment, and - after the radio link failure, updating the set of secondary cells with the new secondary node encryption key without providing user equipment context to the set of secondary cells.

9. The apparatus according to claim 8, configured to provide the user equipment context to the set of secondary nodes before the radio link failure.

10. The apparatus according to any one of claims 8 to 9, further configured to provide instructions to the user equipment for maintaining the SAPC configuration in the event of a radio link failure with a primary cell group.

11. The apparatus according to any one of claims 8 to 10, further configured to: receive the connection reestablishment request or the reconfiguration completion message from the user equipment, wherein the connection reestablishment request or the reconfiguration completion message identifies a secondary cell that satisfies at least one condition included in the SAPC configuration. 12 . The apparatus according to claim 11 , further configured to: send a configuration for starting dual connectivity with the identified secondary cell.

13. The apparatus according to any one of claims 8 to 12, configured to: determine the new secondary node encryption key based at least in part on a secondary node SN counter list, and wherein the apparatus is further configured to: sending, to the user equipment, an instruction for maintaining the SN counter list provided before the radio link failure; or The SN counter list to be used in key generation is sent to the user equipment.

14. A method for communication, comprising: - when operating in dual connectivity, determining in the device a radio link failure with a primary cell set, wherein a selective activation SAPC configuration for primary to secondary cell alternation is stored for the set of secondary cells; - determining a new secondary node encryption key during connection re-establishment of a connection with the primary node after occurrence of the radio link failure with the primary cell group comprising the primary node, based at least in part on a primary node key received from the primary node, and - after the radio link failure, identifying a secondary cell using the SAPC configuration stored before the radio link failure, and connecting to the identified secondary cell based at least in part on the new secondary node encryption key.

15. The method according to claim 14, further comprising: An instruction is received from the network to maintain the SAPC configuration in the event of a radio link failure with a primary cell group.

16. The method according to claim 14 or 15, further comprising: An indication is sent to the network, the indication indicating that after failure of the radio link with the primary cell group, the device is able to use the SAPC configuration stored in the device before failure of the radio link with the primary cell group.

17. The method according to any one of claims 14 to 16, wherein the method comprises: After the radio link with the primary cell group fails, and when one of the following occurs, starting the evaluation of at least one condition included in the SAPC configuration: Before sending a connection reestablishment request to the master node, or Before sending a reconfiguration completion message to the master node.

18. The method according to claim 17, wherein the method comprises: Based on the evaluation of the at least one condition, the secondary cell is identified, wherein the identified secondary cell satisfies the at least one condition, and the method further comprises indicating the identified secondary cell to the primary node in the connection reestablishment request or in the reconfiguration complete message.

19. The method according to claim 18, wherein the method comprises: A configuration for starting dual connectivity with the identified secondary cell is received.

20. A method according to any one of claims 14 to 19, comprising: determining the new secondary node encryption key based at least in part on the secondary node SN counter list, and wherein the method comprises: receiving an instruction to maintain the SN counter list provided before the radio link failure; or The SN counter list to be used in key generation is received.

21. A method for communication, comprising: - when operating as a primary node in a dual connectivity session of a user equipment, providing, by the apparatus, to the user equipment, a selective activation SAPC configuration for a primary and secondary cell change for a set of secondary cells; - determining, after a radio link failure occurs, a new secondary node encryption key based at least in part on the primary node key determined by the apparatus as a response to receiving a connection reestablishment request or a reconfiguration complete message from the user equipment, and - after the radio link failure, updating the set of secondary cells with the new secondary node encryption key without providing user equipment context to the set of secondary cells.

22. The method according to claim 21, comprising: Prior to the radio link failure, the user equipment context is provided to the set of secondary nodes.

23. The method according to any one of claims 21 to 22, further comprising: Instructions are provided to the user equipment to maintain the SAPC configuration in the event of a radio link failure with a primary cell group.

24. The method according to any one of claims 21 to 23, further comprising: The connection reestablishment request or the reconfiguration complete message is received from the user equipment, where the connection reestablishment request or the reconfiguration complete message identifies a secondary cell that satisfies at least one condition included in the SAPC configuration.

25. The method according to claim 24, further comprising: A configuration for starting dual connectivity with the identified secondary cell is sent.

26. A method according to any one of claims 21 to 25, comprising: determining the new secondary node encryption key based at least in part on the secondary node SN counter list, and wherein the method further comprises: sending, to the user equipment, an instruction for maintaining the SN counter list provided before the radio link failure; or The SN counter list to be used in key generation is sent to the user equipment.

27. An apparatus for communication, comprising means for: - when operating in dual connectivity, determining in the device a radio link failure with a primary cell set, wherein a selective activation SAPC configuration for primary to secondary cell alternation is stored for the set of secondary cells; - determining a new secondary node encryption key during connection re-establishment of a connection with the primary node after occurrence of the radio link failure with the primary cell group comprising the primary node, based at least in part on a primary node key received from the primary node, and - after the radio link failure, identifying a secondary cell using the SAPC configuration stored before the radio link failure, and connecting to the identified secondary cell based at least in part on the new secondary node encryption key.

28. An apparatus for communication, comprising means for: - when operating as a primary node in a dual connectivity session of a user equipment, providing the user equipment with a selective activation SAPC configuration for a primary and secondary cell change for a set of secondary cells; - determining, after a radio link failure occurs, a new secondary node encryption key based at least in part on the primary node key determined by the apparatus as a response to receiving a connection reestablishment request or a reconfiguration complete message from the user equipment, and - after the radio link failure, updating the set of secondary cells with the new secondary node encryption key without providing user equipment context to the set of secondary cells.

29. An apparatus for communication, comprising: at least one processing core; and at least one memory storing instructions that, when executed by the at least one processing core, cause the apparatus to at least: - receiving a secondary node encryption key from a node acting as a primary node in a dual connectivity session of a user equipment, and the context of the user equipment as part of the selective activation of SAPC settings for primary and secondary cell change; - receiving a new secondary node encryption key from said node acting as said primary node, whereby said context of said user equipment is not updated, and - after receiving the new secondary node encryption key, receiving a connection request based on the SAPC settings from the user equipment.

30. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least: - when operating in dual connectivity, determining a radio link failure with a primary cell group, wherein a selective activation SAPC configuration for primary to secondary cell change is stored for the set of secondary cells; - determining a new secondary node encryption key during connection re-establishment of a connection with the primary node after occurrence of the radio link failure with the primary cell group comprising the primary node, based at least in part on a primary node key received from the primary node, and - after the radio link failure, identifying a secondary cell using the SAPC configuration stored before the radio link failure, and connecting to the identified secondary cell based at least in part on the new secondary node encryption key.

31. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least: - when operating as a primary node in a dual connectivity session of a user equipment, providing the user equipment with a selective activation SAPC configuration for a primary and secondary cell change for a set of secondary cells; - determining, after a radio link failure occurs, a new secondary node encryption key based at least in part on the primary node key determined by the apparatus as a response to receiving a connection reestablishment request or a reconfiguration complete message from the user equipment, and - after the radio link failure, updating the set of secondary cells with the new secondary node encryption key without providing user equipment context to the set of secondary cells.

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