FIELD

[0001] The present disclosure relates to management of user equipments with plural subscriptions in communication networks, such as cellular communication networks.

BACKGROUND

[0002] User equipments of cellular communication networks may be equipped with subscriber identity modules, SIMs. SIMs may store subscriber information relating to a subscription. SIMs may take the form of a universal SIM, known in the art as a USIM. USIMs may comprise physical SIMs or embedded SIMs, eSIMs. An eSIM is an embedded equivalent of an insertable SIM.

[0003] In the event a user equipment, UE, is registered to two networks using two respective subscriptions of the UE, it is interested in receiving paging messages from both networks to make the UE reachable via both of the networks in which the UE is registered.

SUMMARY

[0004] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims. The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments, examples and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various example embodiments.

[0005] According to a first aspect of the present disclosure, there is provided an apparatus comprising an interface configured to receive subscriber information from a first subscriber identity module of the apparatus and from a second subscriber identity module of the apparatus, and at least one processing core, configured to switch the apparatus to a radio resource control inactive state with respect to a first network while transferring data or monitoring paging in a second network, the first network associated with the first subscriber identity module and the second network associated with the second subscriber identity module.

[0006] According to a second aspect of the present disclosure, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to maintain a user equipment in a radio resource control inactive state with respect to a first network, in which the apparatus is comprised, to enable the user equipment to transfer data or monitor paging in a second network, the first network associated with a first subscriber identity module of the user equipment and the second network associated with a second subscriber identity module of the user equipment.

[0007] According to a third aspect of the present disclosure, there is provided a method comprising receiving subscriber information from a first subscriber identity module of an apparatus performing the method, and from a second subscriber identity module of the apparatus, and switching the apparatus to a radio resource control inactive state with respect to a first network while transferring data or monitoring paging in a second network, the first network associated with the first subscriber identity module and the second network associated with the second subscriber identity module.

[0008] According to a fourth aspect of the present disclosure, there is provided a method, comprising maintaining a user equipment in a radio resource control inactive state with respect to a first network, in which an apparatus performing the method is comprised, to enable the user equipment to transfer data or monitor paging in a second network, the first network associated with a first subscriber identity module of the user equipment and the second network associated with a second subscriber identity module of the user equipment.

[0009] According to a fifth aspect of the present disclosure, there is provided an apparatus comprising means for receiving subscriber information from a first subscriber identity module of the apparatus, and from a second subscriber identity module of the apparatus, and switching the apparatus to a radio resource control inactive state with respect to a first network while transferring data or monitoring paging in a second network, the first network associated with the first subscriber identity module and the second network associated with the second subscriber identity module.

[0010] According to a sixth aspect of the present disclosure, there is provided an apparatus comprising means for maintaining a user equipment in a radio resource control inactive state with respect to a first network, in which the apparatus is comprised, to enable the user equipment to transfers data or monitor paging in a second network, the first network associated with a first subscriber identity module of the user equipment and the second network associated with a second subscriber identity module of the user equipment.

[0011] According to a seventh aspect of the present disclosure, there is provided 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 receiving subscriber information from a first subscriber identity module of the apparatus, and from a second subscriber identity module of the apparatus, and switching the apparatus to a radio resource control inactive state with respect to a first network while transferring data or monitoring paging in a second network, the first network associated with the first subscriber identity module and the second network associated with the second subscriber identity module.

[0012] According to an eighth aspect of the present disclosure, there is provided 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 maintaining a user equipment in a radio resource control inactive state with respect to a first network, in which the apparatus is comprised, to enable the user equipment to transfers data or monitor paging in a second network, the first network associated with a first subscriber identity module of the user equipment and the second network associated with a second subscriber identity module of the user equipment.

[0013] According to a ninth aspect of the present disclosure, there is provided a computer program configured to cause at least the following to be performed by an apparatus, when run: receiving subscriber information from a first subscriber identity module of the apparatus, and from a second subscriber identity module of the apparatus, and switching the apparatus to a radio resource control inactive state with respect to a first network while transferring data or monitoring paging in a second network, the first network associated with the first subscriber identity module and the second network associated with the second subscriber identity module.

[0014] According to a tenth aspect of the present disclosure, there is provided a computer program configured to cause at least the following to be performed by an apparatus, when run: maintaining a user equipment in a radio resource control inactive state with respect to a first network, in which the apparatus is comprised, to enable the user equipment to transfer data or monitor paging in a second network, the first network associated with a first subscriber identity module of the user equipment and the second network associated with a second subscriber identity module of the user equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIGURE 1 illustrates an example system in accordance with at least some example embodiments;

[0016] FIGURE 2 illustrates RRC states; [0017] FIGURE 3 illustrates an example apparatus capable of supporting at least some example embodiments;

[0018] FIGURE 4 illustrates signalling in accordance with at least some example embodiments;

[0019] FIGURE 5 is a flow graph of a method in accordance with at least some example embodiments, and

[0020] FIGURE 6 is a flow graph of a process in accordance with at least some example embodiments.

EMBODIMENTS [0021] User equipments with simultaneous subscriptions, for example to two networks, may maintain states with respect to these two networks based on example embodiments disclosed herein. In particular, a user equipment, UE, may transfer data or receive paging in one network, while maintaining a radio resource control, RRC, inactive state with respect to the other network in which the UE is subscribed. This RRC inactive state is distinct from the RRC idle and RRC connected states, as will be described herein below, and the RRC inactive state may be specific to simultaneous use of multiple subscriptions in the sense that there may also be further RRC inactive states, which are distinct from RRC idle and RRC connected states and not specific to simultaneous use of multiple subscriptions. In connection with entering the RRC inactive state with respect to a network, the UE may provide assistance information to this network to assist this network in contacting the UE during the RRC inactive state, for example while the UE performs operations in the other network. This produces the benefit that the UE is enabled to maintain a more active state than the RRC idle state with respect to both networks and the coexistence of its plural subscriptions is enhanced. The radio resource control inactive state differs from both an radio resource control connected state and a radio resource control idle state.

[0022] FIGURE 1 illustrates an example system in accordance with at least some example embodiments. Illustrated is user equipment, UE, 110. UE 110 may comprise a smartphone, as in FIGURE 1, however the UE may alternatively or additionally be a smart watch, a tablet computer, a laptop computer, a desktop computer, a connectivity module of a connected car, a machine-to-machine communication node, a machine-type communication, MTC, node or an Internet of Things, IoT, node, for example. UE 110 is associated with two subscriptions, enabling it to attach itself to two communication networks, respectively. For example, the two networks may comprise wireless communication networks, such as cellular or non-cellular communication networks, for example. The networks may be public land mobile networks, PLMNs, for example.

[0023] Examples of cellular communication networks include long term evolution, LTE, and fifth generation, 5G, networks as specified by the 3 ^rd generation partnership project, 3GPP. 5G may also be known broadly as new radio, NR, which is the 5G radio interface. Examples of non-cellular communication networks include wireless local area network, WLAN, and worldwide interoperability for microwave access, WiMAX, networks.

[0024] Base station 120 is comprised in a first network, and base station 130 is comprised in a second network. The expression “base station” is used herein as a terminological choice for the sake of clarity. In general the name of a radio access network node depends on the technology in use, for example in LTE this node is known as an eNB and in 5G as a gNB, while in WLAN such a node is known as an access point. However, the expression “base station” will be used herein as a term for a radio access node with which a UE can form a wireless link, without limitation to any specific radio technology.

[0025] Base station 120 is connected with a node 125 of the first network. Node 125 may comprise a radio access network controller or a core network node, for example. Node 125 is connected with further nodes, which are not illustrated in FIGURE 1 for the sake of clarity. Likewise, Base station 130 is connected with a node 135 of the second network. Node 135 may comprise a radio access network controller or a core network node, for example. Node 135 is connected with further nodes, which are not illustrated in FIGURE 1 for the sake of clarity. The first and second networks may have the same network operator, or they may have different network operators. Base stations 120 and 130 and/or nodes 125 and 135 may store information concerning UEs that have RRC states with respect to the first and second networks, respectively. The first and second networks need not be configured to operate based on the same technology. For example, the first network may be a 5G network and the second network may be an LTE network. Alternatively, the first and second networks may act based on the same technology, such as LTE or 5G, for example.

[0026] UE 110 has a subscription to both the first network and the second network. The subscriptions enable UE 110 to attach itself to these networks, using subscriber information of the respective subscriptions. Subscriber information may be stored on a subscriber identity module of the subscription. As UE 110 has two subscriptions, it may have two respective subscriber identity modules. Each of these subscriber identity modules, SIMs, may comprise a universal subscriber identity module, USIM, on an embedded subscriber identity module, eSIM, or a USIM on an insertable integrated circuit card, for example. An eSIM is a programmable SIM embedded directly into the UE as a physical component integrated as part of the UE. An example of a suitable insertable integrated circuit card is a universal integrated circuit card, UICC. UE 110 may thus have, for example, two slots, where the user may insert such circuit cards to provide the UE with the subscriber information, which may be stored on the circuit cards. For processing the subscriber information, UE 110 then has an interface which is electrically connected with the slots, to enable communication with the circuit cards. Where an eSIM identity module is present, the interface of the UE enables communication with the eSIM. In some example embodiments, the UE has one eSIM and one USIM. A SIM, therefore, may comprise a software module stored on an embedded or insertable hardware element.

[0027] In the situation illustrated in FIGURE 1, UE 110 is within the coverage area 102 of the first network, where base station 120 is comprised. Likewise, UE 110 is within the coverage area 103 of the second network, where base station 130 is comprised. Since UE 110 has subscriptions to both of these networks, a first subscription with first subscriber information on first subscriber identity module and a second subscription with second subscriber information on second subscriber identity module, UE 110 can attach to both networks. UE 110 may have RRC states with respect to both networks, also at the same time. The extent to which UE 110 may communicate with the networks simultaneously depends on the technical abilities of the UE, in particular whether it has one or two radios. A wireless link 112 with the base station 120, and a wireless link 113 with base station 130 are illustrated in FIGURE 1. Wireless links may be used to transfer data, but a wireless link is not always necessary to maintain an RRC state with respect to a network.

[0028] One aspect of a UE registered in two networks simultaneously is that the UE should be able to receive paging messages from both networks. A paging message may inform the UE of an incoming telephone call or the presence of pending data for the UE or other events, for example. In case the UE cannot listen at the same time on both networks, the UE may need to skip from network to network according to a pattern, to ensure paging messages are received. A single-receiver, single-Rx, UE is able to receive traffic from only one network at a time, while a dual-Rx UE can simultaneously receive traffic from two networks. Likewise single-Tx and dual-Tx UEs are able to simultaneously transmit in one only and two networks, respectively. While discussed herein as dual SIM with two subscriptions, in more general terms a UE may have three or more subscriptions and SIMs, and be simultaneously registered in three or more networks, respectively. This may be referred to as Multi-SIM, two or more subscriptions.

[0029] A dual-SIM dual-standby, DSDS, UE is registered in two networks simultaneously but uses a single radio front-end and base band chain. Such a UE may, for example, interrupt data transfer on one network to listen for paging on another network. For example, the other network and the UE may have an agreed set of time instances when paging messages may be delivered to the UE. The UE only needs to be monitoring on the other network on these time instances to receive pages, which the other network may buffer until the next one of the agreed time instances.

[0030] Furthermore, a DSDS UE, operating on a first network with an active data connection, should to be able to decide whether to respond to a paging message of a second network. Responding to the paging indication may mean, however, dropping the active data connection on the first network. In the absence of information indicating a service type that triggered the paging, the UE would have to blindly decide whether to ignore the page or respond to it. Further, the UE would in the first place have to make a decision as to whether or not to interrupt the ongoing reception on the first system to monitor for the paging message in the second network. In practical terms the paging message may be, for example, a valid downlink control indicator, DCI, on a physical downlink control channel potentially carrying a paging radio network temporary identifier, RNTI. Alternatively, the paging message may comprise content on a physical downlink shared channel after being indicated by the DCI scrambled with paging RNTI, P-RNTI.

[0031] The time instances for paging, known as paging occasions, PO, may be calculated based on a UE identifier, for example. The international mobile subscriber identity, IMSI, and/or 5G-S-TMSI may be to calculate POs for UEs in the RRC idle and inactive state, for example. The inactive-RNTI, I-RNTI, identifier may additionally or alternatively be used for paging reception/monitoring, such as radio access network-level paging, by a UE in RRC inactive. For example, a paging message may include the I-RNTI to address a UE in the RRC inactive state. In some cases, the UE identifier values associated with the different SIMs can lead to systematic collisions which may result in missed pages across systems. Managing the POs to eliminate, or at least reduce, these collisions would improve performance.

[0032] Example embodiments disclosed herein make uses of the RRC inactive state, which is briefly reviewed in the following. An independent RRC state known as RRC inactive was introduced in 3GPP for release 15 of NR to complement the previously existing states, RRC connected and RRC idle, with the goal of lean signalling and energy- efficient support of services. Although the design was conceived particularly for machine- type or Internet of Things communication, it could be beneficial to efficiently deliver small and/or infrequent traffic for other services as well. The RRC state machinery is illustrated in FIGURE 2. The RRC inactive state enables to more quickly resume the connection and start the transmission of small or sporadic data with a much lower initial access delay and associated signalling overhead as compared to the RRC idle state. This is achieved by reduced control signalling required for requesting and obtaining the resume of a suspended RRC connection, which results in UE power savings. At the same time, a UE in RRC inactive is able to achieve similar power savings as in RRC idle, benefiting from a much longer periodicity of physical downlink control channel monitoring (e.g. for paging) and fewer required measurements than in the RRC connected state. Furthermore, compared to keeping the UE in RRC connected, RRC inactive minimizes mobility signalling both to radio access network, RAN, such as RRC measurement reporting and handover messages, and to the core network, such as with the AMF. When a UE is moved to RRC inactive via an RRC connection suspend message, the UE access stratum, AS, context (referred to as UE inactive AS context), necessary for the quick start of the connection, is maintained both at the UE side and RAN side, and it is identified by the UE identifier, e.g. the inactive- RNTI, I-RNTI. Measurements and associated reporting which is performed in RRC connected state but which is not performed in RRC inactive may include at least one of channel state information reference signal, CSI-RS, channel state information, CSI, and channel quality indicator, CQI. Additionally or alternatively, radio link monitoring, RLM, and/or bidirectional forward detection, BFD, procedures and related measurements may be omitted in RRC inactive state.

[0033] A transition from RRC connected to RRC inactive may be triggered by the base station with the transmission of a RRC release message which includes suspend configuration information. The suspend configuration information may include, for example, at least one of the following: I-RNTI, RAN-PagingCycle, RAN- NotificationArealnfo and a timer t380 which refers to the timer that controls when the periodic radio access network based notification area update, RNAU, procedure should occur at the UE.

[0034] In release 17, 3GPP has a work item entitled “NR small data transmissions in INACTIVE state”. The main motivation is to avoid signalling overhead and delay associated with transition from RRC inactive state to RRC connected state to perform a short data transmission. This functionality is interesting since the motivation to introduce the RRC inactive state was to be able to transition UEs with infrequent data transmission to a state with minimum signalling overhead and power consumption. In this context, the short data transmission may be performed in a random access procedure in e.g. the “MsgA” or “Msg3” message, or the short data may be transmitted using pre-configured configured-grant based resources on physical uplink shared channel.

[0035] When a single-Rx / DSDS UE is listening to paging or having data transfer related to one network, it may have to skip or drop paging monitoring from one or more other networks, thus introducing a delay in the communication with that network. In turn, that network would continue paging the non-responsive UE, due to its activity towards another network, until a response is received, leading to unnecessary paging signalling. Methods are disclosed herein which use the RRC inactive state to address this problem.

[0036] According to at least some example embodiments disclosed herein, a multi- SIM UE may be allowed to move to the RRC inactive state with respect to Network A while providing assistance information to Network A, where this information may assist or guide the “non-active” Network A to use a specific UE identifier to contact the UE during the RRC inactive state, and the UE will return to Network A when it is fully available again, after it completes its actions in Network B. For example, the assistance information may specify an I-RNTI that Network A may use to determine paging occasions and to perform the paging, and/or the assistance information may specify a minimum priority level of data that the UE is willing to interrupt its actions in Network B for. Additionally or alternatively, the assistance information may comprise an estimate of how long the actions in Network B will take, before the UE will return to Network A.

[0037] The UE in RRC connected state in Network A may be configured with a specific RRC inactive configuration for Multi-SIM configuration including an I- RNTI musim and RNA musim, these for Multi -USIM use, to use when the UE needs to move to another network, referred to here as Network B. This allows the UE to remain in RRC inactive state in Network A using a longer paging cycle while performing operations, such as data transfer or reception of paging, in Network B. Network A may signal the presence of priority traffic by paging with the I-RNTI musim identifier. Paging occasions for Network A may be less frequent in the Multi-SIM RRC inactive state than in a normal RRC inactive state.

[0038] The RRC inactive configuration for Multi-SIM configuration may differ from a regular RRC inactive configuration as follows: [0039] According to a first difference, its resume can be initiated either by the UE or by the network. In some example embodiments, the network resume can occur only after receiving an RNAU message from the UE, indicating its availability, or due to the presence of high priority traffic.

[0040] According to a second difference, the UE could be configured with two potentially independent RRC inactive configurations, a regular one and one for Multi-SIM. The latter could comprise a longer DRX/paging cycle as compared to the regular one to allow the UE’s operations in the other network, with respect to which the UE is not RRC inactive. Similarly, also the periodicity of the periodic RNAU for Multi-USIM purposes may be made also longer to minimize interruptions when the UE operates in Network B.

[0041] According to a third difference, when in RRC inactive with two configurations, the UE monitors paging for more than one I-RNTI identifier. Each I-RNTI identifier may be associated with a specific RRC inactive configuration.

[0042] According to a fourth difference, if the network pages the UE targeting the page message to the I-RNTI musim identifier, it indicates that it has higher priority traffic for the UE and expects the UE to become available as soon as possible; otherwise, if it pages the UE with regular I-RNTI, it is left up to the UE whether to interrupt ongoing operations in the other network or not.

[0043] In the above, one additional RRC inactive configuration has been discussed, but without loss of generality this could be expanded to cover multiple configurations, where different I-RNTI musim values could be configured and mapped to different service types. The I-RNTI musim values could be configured to allow using the same paging occasion for the indication of different service type(s) or to cover different, for example adjacent, paging occasions to allow for UE monitoring for different service types at different time instants. The latter option would be useful for allowing more flexibility in the network for scheduling paging UEs. The UE may select an RRC inactive configuration to use with respect to Network A based on which service the UE plans to engage in Network B. If the service in Network B is of high-priority, the UE may select a RRC inactive configuration which allows interruption of the service only with even higher priorities, such as emergency messaging, for example. Likewise, in case the service in Network B is sensitive to delay, an RRC inactive configuration with a longer paging occasion interval may be selected. In general, high-priority data may comprise data where a priority indicator indicates a priority of the data exceeds a preconfigured threshold priority. For example, if the threshold is 3 and priority increases with numerical value, data with a priority of 4 or more would be high-priority data.

[0044] A UE may have more than one RRC inactive configuration, for example one RRC inactive configuration for legacy RRC inactive operations and one for Multi-SIM purposes. Further, the RRC inactive configuration for Multi-SIM may be provided with a RRC setup or a reconfiguration message, for example.

[0045] Concerning the four differences laid out above, various example embodiments may comprise different combinations of these differences. For example, an example embodiment may comprise exactly one of the first, second, third and fourth difference. On the other hand, an example embodiment may comprise all of the four differences. Further, an example embodiment may comprise the first and the second difference only, or the first, second and third difference only. Yet further options are the second and third difference only, and the second, third and fourth difference only. Also possible is a combination of the third and fourth difference only.

[0046] In some example embodiments, as part of the Multi-SIM configuration, the UE receives a maximum time during which it can operate in a different network without monitoring paging in this network. This period could be configured in terms of the UE’s current paging cycle, for example.

[0047] To activate the RRC inactive configuration in Network A, the UE may either request from Network A the activation of the RRC inactive configuration for Multi-SIM, or it may start using an available configuration after notifying its use to the network, for example by sending an RRC suspend request for Multi-SIM operation message with a cause set to switch-out from Network A.

[0048] The RRC suspend request message may further include an indication about the target network and the estimated interruption time affecting Network A, depending, for example, on the applications running at the UE and/or an indication provided from Network B. The indication may comprise a priority of the service, the type of service, the configured gaps, for example. The indication provided in the RRC suspend message may be comprised in the assistance information mentioned above. [0049] The RRC suspend request message may be implemented as an RRC resume message by setting the value of a resume cause in the message to switch-out from Network A.

[0050] When the UE is in RRC inactive with respect to Network A, it may behave similarly as in RRC idle toward Network A, monitor paging on Network A with a longer paging period, while performing operations, such as data transmission or reception of paging, towards Network B. The paging period, or paging periods, may differ from those in RRC idle.

[0051] Upon completing its operations in Network B and/or if Network A has priority traffic, or if a trigger is met to access Network A, the UE may notify Network A about its switching back to Network A. This notifying may comprise, for example, sending an RNAU message with cause value set to switch-back to Network A.

[0052] The RNAU message may comprise a “network-switch” event-based RNA update or a periodic RNA update with, for example, a cause value indicating that the UE has switched back, or will switch back, to Network A. The UE indication of switch-back to Network A may be provided using a dedicated physical random access channel, PRACH, preamble or dedicated physical uplink shared channel, PUSCH, resources, for example. For example, 2-step RACH mechanisms or configured grant-based small data transmission may be employed.

[0053] After receiving such a notification, Network A can resume the RRC connection of the UE. In one variant of this example embodiment, the RNAU message indicates that the UE has completed its activities on Network B, and hence would be switching back to the normal RRC inactive mode, thereby starting using its normal I-RNTI and associated paging monitoring periodicities and not the ones defined for Multi-SIM.

[0054] FIGURE 2 illustrates the RRC states in a new radio, NR, example. States may be similar in other technologies as well. The RRC inactive state corresponds to a situation where a UE AS context is stored in the UE and the radio access network, and furthermore a connection between RAN and the core network is maintained open for the UE. Thus no latency is incurred from resuming this connection once the UE resumes an RRC connected state with respect to the network. In the RRC idle mode, only cell selection and reselection mobility procedures are supported, enabling roaming. No context is maintained for UEs in RRC idle state. On the other hand in RRC connected mode, more active mobility procedures are supported which may include active / serving cell set updating, (hard) handover, inter-system handover and/or cell update. The RRC connected mode also involves performing measurements to support these mobility procedures.

[0055] FIGURE 3 illustrates an example apparatus capable of supporting at least some example embodiments. Illustrated is device 300, which may comprise, for example, a mobile communication device such as UE 110 of FIGURE 1. In applicable parts, device 300 may also correspond to a network-side node such as a base station or node 125/135. Comprised in device 300 is processor 310, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 310 may comprise, in general, a control device. Processor 310 may comprise more than one processor. Processor 310 may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core designed by Advanced Micro Devices Corporation. Processor 310 may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor 310 may comprise at least one application-specific integrated circuit, ASIC. Processor 310 may comprise at least one field-programmable gate array, FPGA. Processor 310 may be means for performing method steps in device 300, such as receiving, maintaining and transferring. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0056] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with example embodiments described herein. As used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a UE or network node, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor s) or a portion of a microprocessor s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0057] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0058] Device 300 may comprise memory 320. Memory 320 may comprise random- access memory and/or permanent memory. Memory 320 may comprise at least one RAM chip. Memory 320 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 320 may be at least in part accessible to processor 310. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be means for storing information. Memory 320 may comprise computer instructions that processor 310 is configured to execute. When computer instructions configured to cause processor 310 to perform certain actions are stored in memory 320, and device 300 overall is configured to run under the direction of processor 310 using computer instructions from memory 320, processor 310 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be at least in part external to device 300 but accessible to device 300.

[0059] Device 300 may comprise a transmitter 330. Device 300 may comprise a receiver 340. Transmitter 330 and receiver 340 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 330 may comprise more than one transmitter. Receiver 340 may comprise more than one receiver. Transmitter 330 and/or receiver 340 may be configured to operate in accordance with global system for mobile communication, 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, for example. [0060] Device 300 may comprise a near-field communication, NFC, transceiver 350. NFC transceiver 350 may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

[0061] Device 300 may comprise user interface, UI, 360. UI 360 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 300 to vibrate, a speaker and a microphone. A user may be able to operate device 300 via UI 360, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 320 or on a cloud accessible via transmitter 330 and receiver 340, or via NFC transceiver 350, and/or to play games.

[0062] Device 300 may comprise or be arranged to accept a user identity module 370. User identity module 370 may comprise, for example, a subscriber identity module, SIM, card installable in device 300. Processor 310 may access subscriber information of the user identity module 270 via an interface which is comprised in device 300. Such an interface may comprise an electrical connection to a SIM card slot, for example. A user identity module 370 may comprise information identifying a subscription of a user of device 300. A user identity module 370 may comprise cryptographic information usable to verify the identity of a user of device 300 and/or to facilitate encryption of communicated information and billing of the user of device 300 for communication effected via device 300.

[0063] Processor 310 may be furnished with a transmitter arranged to output information from processor 310, via electrical leads internal to device 300, to other devices comprised in device 300. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 320 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 310 may comprise a receiver arranged to receive information in processor 310, via electrical leads internal to device 300, from other devices comprised in device 300. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 340 for processing in processor 310. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver. [0064] Device 300 may comprise further devices not illustrated in FIGURE 3. For example, where device 300 comprises a smartphone, it may comprise at least one digital camera. Some devices 300 may comprise a back-facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the front- facing camera for video telephony. Device 300 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 300. In some example embodiments, device 300 lacks at least one device described above. For example, some devices 300 may lack a NFC transceiver 350 and/or user identity module 370.

[0065] Processor 310, memory 320, transmitter 330, receiver 340, NFC transceiver 350, UI 360 and/or user identity module 370 may be interconnected by electrical leads internal to device 300 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 300, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the example embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0066] FIGURE 4 illustrates signalling in accordance with at least some example embodiments. On the vertical axes are disposed, on the left, base stations 120 and 130, and UE 110 on the right. Time advances from the top toward the bottom.

[0067] In phase 410, UE 110 invokes the RRC inactive state with Multi-SIM configuration toward the first network, in which base station 120 is comprised. As discussed above, this may comprise transmission of a suitable RRC connection release with a suspend configuration (RRC suspend in short) or RRC resume message. An RRC suspend may comprise an indication of the second network, in which base station 130 is comprised. The RRC suspend may further include an estimated time of the Multi-SIM RRC inactive state with respect to the first network. In case an RRC resume message is used, it may comprise the same indications of network and, optionally, estimated time, as assistance information.

[0068] In phase 420, UE 110 engages with base station 130, for example to transfer data or to receive paging. While phase 420 is ongoing, UE 110 is in the Multi-SIM RRC inactive state with respect to the first network. [0069] In phase 430, the first network determines it has high-priority traffic for UE 110. This determination may be performed in base station 120, as illustrated, or in node 125, for example. Responsive to this determination, this network determines the next paging occasion of UE 110, for example using the I-RNTI specific to the RRC inactive state Multi-SIM configuration. At this paging occasion, phase 440, this network pages UE 110, the paging message indicating the presence of high-priority traffic. In response UE 110 interrupts its activity with base station 130 and returns to the network of base station 120 to make itself available for the high-priority traffic, phase 450.

[0070] FIGURE 5 is a flow graph of a method in accordance with at least some example embodiments. The phases of the illustrated method may be performed in device 110, an auxiliary device or a personal computer, for example, or in a control device configured to control the functioning thereof, when installed therein.

[0071] Phase 510 comprises receiving subscriber information from a first subscriber identity module of an apparatus performing the method, and from a second subscriber identity module of the apparatus. Phase 520 comprises switching the apparatus to a radio resource control inactive state with respect to a first network while transferring data or monitoring paging in a second network, the first network associated with the first subscriber identity module and the second network associated with the second subscriber identity module. Finally, optional phase 530 specifies, that the radio resource control inactive state differs from both a radio resource control connected state and a radio resource control idle state. For example, the radio resource control inactive state may comprise a radio resource control inactive state for Multi-SIM. Alternatively or additionally to monitoring paging, the method may comprise receiving paging. The apparatus may be in a radio resource connection connected state with respect to the first network prior to the switching, and/or the UE may activate a received RRC inactive state configuration of for Multi-SIM before switching to the second network. The radio resource control inactive state differs from both an radio resource control connected state and a radio resource control idle state. In an example embodiment, the first and second networks are associated with a same public land mobile network, PLMN.

[0072] FIGURE 6 is a flow graph of a process in accordance with at least some example embodiments. In phase 610, a UE is provided the RRC inactive configuration for Multi-SIM, which includes the I-RNTI musim and an RNA musim from Network A. In phase 620, the UE determines whether a trigger is met to switch-out from Network A to Network B. In the event this is the case, processing advances to phase 630, where the UE invokes the RRC inactive configuration for Multi-SIM, for example by sending the RRC Suspend invoking the Multi-SIM RRC inactive state with respect to Network A. A switch- out indication may be provided.

[0073] The UE will then interact with Network B, phase 640, as it enters the Multi- SIM RRC inactive mode with respect to Network A. In phase 650, the UE determines whether a trigger, such as a high-priority page using I-RNTI musim, has occurred, and in the event this is the case, phase 660, the UE returns to Network A. This may comprise sending the RNAU message to Network A with the switch-back indication discussed above.

[0074] It is to be understood that the example embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular example embodiments only and is not intended to be limiting.

[0075] Reference throughout this specification to one example embodiment or an example embodiment means that a particular feature, structure, or characteristic described in connection with the example embodiment is included in at least one example embodiment of the present invention. Thus, appearances of the phrases “in one example embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0076] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various example embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such example embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0077] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of example embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0078] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0079] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[0080] At least some embodiments of the present invention find industrial application in managing communication networks.

ACRONYMS LIST AMF access and mobility management function

DCI downlink control indicator

DRX discontinuous reception IMSI international mobile subscriber identity

RNAU radio access network based notification area update RNA radio access network based notification area RNTI radio network temporary identifier RRC radio resource control

TMSI temporary mobile subscriber identity

REFERENCE SIGNS LIST