Sending a busy indication

Abstract

In an example, a method in a User Equipment (UE) of sending a busy indication is provided. The UE is equipped with a plurality of Universal Subscriber Identity Modules (USIMs), including a first USIM associated with a first network and a second USIM associated with a second network. The method comprises, if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, sending the busy indication to the second network.

Description

[0001] SENDING A BUSY INDICATION

[0002] Technical Field

[0003] Example embodiments of this disclosure relate to sending a busy indication, for example by a User Equipment (UE) is equipped with multiple Universal Subscriber Identity Module (MUSIM).

[0004] Background

[0005] Multi-USIM (MUSIM) is a term used to describe a feature wherein multiple Universal Subscriber Identity Modules (USIMs), i.e. multiple subscriptions, are used at a single wireless communications device, such as a single UE or smartphone. The multi-USIM feature has been commercialized worldwide in various markets and has become a common feature supported by major device manufacturers. For example, the Apple® iPhone® 12 supports multi-USIM with 2 physical SIM cards in China, while in other regions it supports one physical SIM card and one eSIM.

[0006] The type of MUSIM supported in legacy UEs is the Dual SIM Dual Standby (DSDS) type of operation, which means only one of the USIMs in a device can be actively connected in RRC Connected mode in one PLMN to send and / or receive data. Other USIM(s) in the device can be in RRC idle or inactive mode in another PLMN (i.e. on standby) in case there is a request to be actively connected to that PLMN. This is based on a device architecture including single or dual receivers (Single-Rx or Dual-Rx) together with a single transmitter (Single-Tx), which is regarded as a legacy UE architecture, supporting up to 3GPP Release 17 (Rel-17).

[0007] It is the Single-Tx that limits the device’s Multi-USIM operation to be actively in connected mode in only one PLMN, and in idle / inactive in the PLMN(s), as there is no possibility for uplink (UL) feedback to the other PLMN(s) while the Single-Tx is occupied by UL transmission in the first PLMN.

[0008] In Rel-17, the MUSIM work item (Wl) brings several improvements over the legacy MUSIM solutions, for example the opportunity for the UE to coordinate the multiple USIMs to avoid paging occasion collisions. The MUSIM Wl provides signaling solutions for the UE to inform the network on the UE’s preferred MUSIM gaps, and for the network to send the corresponding MUSIM gap configurations to the UE. By using MUSIM gaps, the UE can coordinate different activities towards the respective networks more efficiently, for example for monitoring paging. The MllSIM gaps configured in the first PLMN allows the UE to momentarily switch to another PLMN to perform certain activities, even while remaining in connected mode in the first network. This is referred to as MllSIM gap coordination as explained below. MllSIM gaps are defined in 3GPP TS 38.133 v17.10.0.

[0009] The Rel-17 RRC specification (3GPP TS 38.331 v17.8.0) on MllSIM gap coordination concerns mainly two parts: the UE Assistance Information (UAI) including the MUSIM assistance information; and the MUSIM gap configuration. The UAI is sent from the UE to the network and includes the UE’s preferred MUSIM gap information. The MUSIM gap configuration is part of the RRC Reconfiguration, which is sent from the network to the UE describing the MUSIM gap that the network has accepted, and that the UE may use. Both the UAI and the MUSIM configuration can use the same information elements, such as MUSIM-Gaplnfo-r17, which guarantees that the same form of information is used both at the UE side in the UAI and the network side as the actual MUSIM gap configuration. The UAI information including MUSIM-Assistance-r17 is defined in 3GPP TS 38.331 v17.5.0.

[0010] In 3GPP Release 18 (Rel-18), 3GPP continued working on Multi-SIM (also referred to as MUSIM) in a new work item (Wl), RP-233071, “Dual Transmission / Reception (Tx / Rx) Multi- SIM for NR,” with justification as follows:

[0011] MUSIM UE's hardware capabilities are shared by the SIMs, and to use the hardware efficiently and economically, the related capabilities need to be dynamically split between the two SIMs. This can lead to a temporary hardware conflict for the UE, which may require UE to release some resources (e.g. SCell / SCG) from one SIM. For example, when the UE’s SIM A is in RRC connected state in NW A while the UE’s SIM B is in RRC Idle or RRC Inactive in NW B, the two RF chains will be occupied by the SIM A for the communication in NW A. Once the UE’s SIM B enters into RRC connected state, one of the RF chains needs to be switched to SIM B. In this case, if the NW A is not aware of the UE’s reduced capability change in RF chain, there may be data loss due to demodulation failure and wasting radio resources in NW A. To avoid this, assistance from UE to network A on these temporary UE (capability) restrictions can be beneficial.

[0012] The objectives included in this Rel-18 Wl are as follows, based on a new UE architecture as Dual Rx / Dual-Tx UE. Enhancements for MU SIM procedures to operate in RRC_CONNECTED state simultaneously in NW A and NW B. [RAN2, RAN3, RAN4J.

[0013] • Specify mechanism to indicate preference on temporary UE capability restriction and removal of restriction (e.g. capability update, release of cells, (de) activation of configured resources) with NW A when UE needs transmission or reception (e.g., start / stop connection to NW B) for MUSIM purpose

[0014] • RA T Concurrency: Network A is NR SA (with CA) or NR DC. Network B can either be LTE orNR.

[0015] • Applicable UE architecture: Dual-RX / Dual-TX UE

[0016] The work item shall identify whether the Wl will have RAN3 or RAN4 impacts by RAN#99 [RAN2J.

[0017] Therefore, Dual-Tx, which is a mandatory architecture to support Dual Connectivity (DC) or Carrier Aggregation (CA), now benefits the Multi-SIM feature so each of the USIMs can be in active mode in different PLMNs with two or more UL (and DL) chains to support the UL feedback loops. The objective is to specify a mechanism to indicate preference on temporary UE capability with the possibility of releasing the UE capability from one USIM / PLMN, so that the UE will leave DC / CA and free up one Tx / Rx which the UE may use for the other USIM / PLMN. This enables the UE to use both USIMs to connect to both PLMNs simultaneously using one USIM for each PLMN. Furthermore, the objective is also to specify mechanisms such that the UE can leave one PLMN and reenable CA or DC in the other PLMN.

[0018] When a UE with Single Tx and Single or Dual Rx is in RRC Connected state in one network (e.g. PLMN1) and in RRC Idle or Inactive in the other network (e.g. PLMN2), it can monitor for incoming Paging messages in PLMN2 by using MUSIM gaps in PLMN1. In Rel-17, 3GPP TS 38.331 v17.8.0, a Paging Cause indication was introduced in the Paging message, which the network may use to indicate if the Paging message was sent because of an incoming voice call, for example.

[0019] In case a Paging message is received from PLMN2, a Busy Indication procedure (also referred to in some examples as a Reject Paging Request) has been introduced by 3GPP in Rel-17 for MUSIM UEs and it is described in 3GPP TS 23.501, 17.12.0. In that case, the UE can send a “Busy Indication” to the network to indicate that the Paging has been received but it will not be responded to. The “Busy indication” procedure consists in transitioning to RRC Connected (e.g. from RRC Idle or Inactive) in the second PLMN for setting up a connection in order to send a Non Access Stratum (NAS) Service Request message including a Reject Paging Indication to the network indicating that the UE does not accept the paging and requests, and returning to the RRC Idle state. In addition to the Reject Paging Indication, the UE may include the Paging Restriction Information, which requests the network to restrict the paging messages sent to the UE. The Paging Restriction Information may indicate any of the following:

[0020] • all paging is restricted; or

[0021] • all paging is restricted, except paging for voice service (IP Multimedia Subsystem, IMS, voice); or

[0022] • all paging is restricted, except for certain Protocol Data Unit (PDU) Session(s); or

[0023] • all paging is restricted, except paging for voice service (IMS voice) and certain PDU session(s).

[0024] Depending on which type of restriction is indicated, the UE expects to receive fewer or no Paging messages from the network.

[0025] In Rel-18 there is no discussion yet on how the busy indication should be implemented. The UE may also have different alternatives to the busy indication: the UE may decide to respond to the Paging, which means that the ongoing service in PLMN1 has to be interrupted at least temporarily, or ignore the Paging.

[0026] 3GPP standard specifications include the possibility for a multi-USIM UE to send a busy indication (e.g. Reject Paging Indication) to a network in response to a paging message in that network, the busy indication indicating that the UE does not accept the incoming paging. However, the standard does not describe when and / or under what condition(s) the UE will (or will not) trigger the procedure(s) to send the busy indication to the second network. These conditions are left to UE implementation, i.e. are not specified by 3GPP.

[0027] Examples of this disclosure may provide UE implementation solutions for the UE to decide under what conditions to trigger the procedure of sending a busy indication in a second network, and under what conditions not to trigger such procedure and instead ignore the paging message or to respond to it. When the UE decides to trigger the procedure of sending a busy indication, it can in some examples indicate which services can be paged by the second network, and this can in some examples provide the possibility to limit the number of MllSIM gaps the UE needs in the first network to monitor the second network. When the UE decides not to trigger the procedure of sending a busy indication, it may in some examples avoid interruption of an ongoing service in the first network, and may therefore provide a better quality to the ongoing service in the first network.

[0028] One aspect of the present disclosure provides a method in a User Equipment, UE, of sending a busy indication. The UE is equipped with a plurality of Universal Subscriber Identity Modules, USIMs, including a first USIM associated with a first network and a second USIM associated with a second network. The method comprises, if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, sending the busy indication to the second network.

[0029] Another aspect of the present disclosure provides apparatus in a User Equipment, UE, for sending a busy indication. The UE is equipped with a plurality of Universal Subscriber Identity Modules, USIMs, including a first USIM associated with a first network and a second USIM associated with a second network. The apparatus comprises a processor and a memory. The memory contains instructions executable by the processor such that the apparatus is operable to, if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, send the busy indication to the second network.

[0030] A further aspect of the present disclosure provides apparatus in a User Equipment, UE, for sending a busy indication. The UE is equipped with a plurality of Universal Subscriber Identity Modules, USIMs, including a first USIM associated with a first network and a second USIM associated with a second network. The apparatus is configured to, if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, send the busy indication to the second network.

[0031] Brief Description of the Drawings

[0032] For a better understanding of examples of the present disclosure, and to show more clearly how the examples may be carried into effect, reference will now be made, by way of example only, to the following drawings in which: Figure 1 is a flow chart of an example of a method in a User Equipment (UE) of sending a busy indication; and

[0033] Figure 2 is a schematic of an example of an apparatus 200 in a User Equipment, UE, for sending a busy indication.

[0034] Detailed Description

[0035] The following sets forth specific details, such as particular embodiments or examples for purposes of explanation and not limitation. It will be appreciated by one skilled in the art that other examples may be employed apart from these specific details. In some instances, detailed descriptions of well-known methods, nodes, interfaces, circuits, and devices are omitted so as not obscure the description with unnecessary detail. Those skilled in the art will appreciate that the functions described may be implemented in one or more nodes using hardware circuitry (e.g. analog and / or discrete logic gates interconnected to perform a specialized function, Application Specific Integrated Circuits (ASICs), Programmable Logic Arrays (PLAs), etc.) and / or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, where appropriate the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

[0036] Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g. digital or analogue) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and / or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

[0037] Figure 1 is a flow chart of an example of a method 100 in a User Equipment (UE) of sending a busy indication. The UE is equipped with a plurality of Universal Subscriber Identity Modules (USIMs), including a first USIM associated with a first network and a second USIM associated with a second network. The UE may also have additional USIM(s) in some examples, though only the first and second USIMs are referred to in this example.

[0038] Each of the first and second networks may be for example a Public Land Mobile Network (PLMN) or another type of network, such as for example a Non Public Network (NPN) or private network. The first network may be the same network as the second network in some examples, for example where the first and second USIMs are associated with the same network. Alternatively, in some examples, the first and second networks may be different networks. Even though examples of this disclosure are described in terms of a UE equipped with two USIMs associated with two networks, in other examples the UE may have more than two USIMs associated with more than two networks, and methods described herein can be applied to such examples.

[0039] The method 100 comprises, in step 102, if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, sending the busy indication to the second network. Thus, for example, if the UE determines an upcoming occasion where it will establish a service, it may, if there is sufficient time before the service is established, send the busy indication to the second network. Examples of this disclosure may thus, for example, ensure that the UE is not disturbed by or does not receive unwanted paging in the second network while a service is ongoing in the first network.

[0040] Examples of when the UE may be aware of an upcoming occasion where it will establish a service may include the following. When a user (referred to as a calling party) initiates a voice call to another user (referred to as a called party), the call setup will take some time. The signaling for setting up the voice call is usually sent over a signaling bearer while the audio will typically be sent over a dedicated bearer, and the network needs to check if resources are available for the voice call, which takes some time. During the call setup phase, the networks will also wait for the called party to accept the call, which also takes some time. The dedicated bearers will be started only if the called party accepts the call. In this case, the UE knows ahead of time that a service is expected to be started quite soon, but there will be some waiting time before the service will start. This waiting time could be used to send the busy signal to the other network. Since the UE knows that the user (calling party) wants to start a voice call, it may even in some examples delay the call setup signaling in the first network to create a time window for sending the busy signal to the second network. In typical cases, the call setup usually takes several seconds, even if the called party accepts the call immediately. Adding a short delay for sending the busy signal to the second network will increase the session setup delay a little, but this is unlikely to be noticeable for the calling and / or called party. The extra delay may be for example in the order of a few hundred milliseconds, which is relatively short compared to the normal call setup time which is in the order of seconds. Another example where the UE may be aware of an upcoming occasion where it will establish a service is when starting a streaming service. For example, when starting a streaming service, the UE (e.g. a client application on the UE) sends an HTTP message to a server and then waits for the server to start the service. This will take some time. In addition, in some examples, the UE may buffer several seconds of media before starting to play the media. In this case, the UE can send the busy signal in the second network while waiting for the server to respond. The client may even in some examples delay sending the initial HTTP message to create a time window that can be used for sending the busy signal in the second network. Similar to the example above, starting a streaming service would normally take several seconds, so adding a few hundred milliseconds to send the busy signal in the second network is unlikely to be noticeable for the user.

[0041] In some examples, the method 100 may comprise determining that the UE will transition to a connected state in the first network at the first time instant. That is, for example, the service in the first network may involve the UE transitioning to the RRC connected state in the first network.

[0042] In a particular example, the UE may determine that it will establish a service in the first network in response to a paging message received in the first network, for example in a paging occasion (PO) configured for the UE in the first network, where the paging message leads to a transition to RRC connected state in the first network. For example, the UE may be in an idle or inactive state in the first network and in an idle or inactive state in the second network, and receives a paging message in the first network. If there is sufficient time, e.g. if the first time period is at least as long as the second time period, the UE does not wait to be paged in the second network but transmits a busy indication to the second network, so that it does not receive by a paging message in the second network while it is in the connected in the first network. Advantages include the following in some examples. First, the UE doesn’t have to monitor paging occasions in the second network or can ignore some or all paging messages in the second network. As a result, there may be no, fewer or shorter interruptions for the service in the first network, which may lead to improved quality for the service. Secondly, the second network knows that there is no point in paging the UE (at least for a subset of paging messages, in examples described below where the busy indication indicates a subset of paging messages the UE would prefer not to receive), since the UE may not monitor for or respond to such paging messages. This may for example avoid paging escalation in the second network, and may thus save signaling resources and energy in the second network. Non-limiting examples of services in the first network may include one or more of a voice call, video call, critical service, Ultra Reliable Low Latency (URLLC) service, real time service, software update of the UE in the first network, and / or one or more measurements in the first network. A “critical service” in this context may be for example a service for which the UE should not have interruptions, e.g. gaps or scheduling restrictions (such as MUSIM gaps), for example, an URLLC service, a voice call or video call.

[0043] The UE may in some examples have at least two independent receiver (Rx) chains and / or at least two independent transmitter (Tx) chains. Thus, in some examples, the UE may have a 3GPP Rel-17 baseline UE architecture of Single (Dual)-Rx / Single Tx UE. In some examples, the UE may have a more advanced UE architecture as Dual-Rx / Dual-Tx UE architecture. In some examples, the UE is capable of Carrier Aggregation (CA) or Dual Connectivity (DC) on at least one of the networks associated with at least one of the USIMs in the UE. However, in some examples, the UE may have a single receiver chain and a single transmitter chain.

[0044] Sending the busy indication to the second network in step 102 of the method 100 may comprise, for example, transitioning to a connected state in the second network, sending the busy indication to the second network, and transitioning to idle state in the second network. For example, the UE may transition to the connected state by transmitting an RRC resume request message in the second network (in case the UE is in an inactive state in the second network), or by transmitting an RRC setup request message in the second network (in case the UE is in an idle state in the second network).

[0045] In some examples, the UE may send to the first network a request for an aperiodic MUSIM gap in which to transmit the busy indication to the second network. The request may specify details for the aperiodic MUSIM gap, such as for example a start time and / or length for the aperiodic MUSIM gap. If an aperiodic MUSIM gap is granted or configured by the first network, the UE may then send the busy indication in step 102 of the method 100 in the aperiodic MUSIM gap.

[0046] The second time period for sending the busy indication to the second network may comprise or include one or more of the following non-limiting examples:

[0047] • a time period for switching the UE from the first network to the second network (e.g. the time needed to switch a transceiver of the UE from one frequency (for the first network) to another frequency (for the second network); • a time period for establishing a Radio Resource Control (RRC) connection in the second network and / or transitioning to RRC connected mode in the second network;

[0048] • a time period for transmitting the busy indication in the second network;

[0049] • a time period for returning to RRC idle mode in the second network; and / or

[0050] • a time period for switching the UE from the second network to the first network.

[0051] In some examples, the second time period includes all of these examples. So, for example, the second time period may include a time period for switching the UE from the first network to the second network, a time period for establishing a RRC connection in the second network, a time period for transmitting the busy indication in the second network, a time period for returning to RRC idle mode in the second network, and a time period for switching the UE from the second network to the first network. Therefore, in some examples, the UE may transmit the busy indication to the second network if the first time period before the UE establishing the service in the first network is at least as long as the total time period for switching the UE from the first network to the second network, establishing a RRC connection in the second network, transmitting the busy indication in the second network, returning to RRC idle mode in the second network, and switching the UE from the second network to the first network.

[0052] The method 100 may in some examples comprise receiving a paging message in the second network before determining that the UE will establish the service in the first network. Thus, in some examples, sending the busy indication in step 102 of the method 100 may be performed in response to the paging message in the second network. The paging message may in some examples be received in a paging occasion (PO) in the second network, PCs being described more fully below. In some examples, sending the busy indication to the second network in step 102 may comprise sending a reject paging indication to the second network, for example as a response to the paging message. Thus, in some examples, the reject paging indication may be an example implementation of the busy indication. The UE may also in some examples ignore the paging message as it is aware that there is an upcoming service in the first network.

[0053] In some examples, the UE may be configured with a plurality of Multiple USIM (MUSIM) gaps in the first network. The UE may also be configured with one or more paging occasions (POs) in the second network in one or more of the MUSIM gaps. Paging occasions are occasions where the UE may receive paging in the second network, and hence may monitor for paging in the second network. The UE may, in some examples, after determining that the UE will establish the service in the first network, send an indication to the first network that no MUSIM gaps or fewer MUSIM gaps are preferred by the UE in the first network. As a result, the UE may have no paging occasions (POs) or fewer POs in the second network while the service is ongoing in the first network. The method 100 may therefore also in some examples include, after ending the service in the first network, sending an indication to the first network that MUSIM gaps, or an increased number of MUSIM gaps, are preferred by the UE in the first network. Thereafter, the UE may again monitor for paging in the second network in POs configured in the MUSIM gaps in the first network, and may therefore be able to respond once again to paging messages in the second network.

[0054] For example, when the UE transmits the busy indication to the second network, the UE also transmits to the first network a message (e.g. UE Assistance Information) including MUSIM gap preference information, indicating to the first PLMN that it does not need (or it prefers to not have) a MUSIM gap, or that it prefers shorter and / or less frequent MUSIM gap(s). Thus, signalling overhead may for example be saved in the second network, as no paging may be sent to the UE by the second network where the UE does not wish to receive the paging or is not expected to respond to the paging in the second network.

[0055] In some examples, the busy indication indicates that all paging in the second network is restricted, e.g. the UE would prefer not to receive any paging messages in the second network. Alternatively, the busy indication may indicate for example that a subset of paging messages in the second network is restricted, e.g. that the UE would prefer not to receive any paging messages belonging to the subset, but would prefer to receive paging messages that do not belong to the subset. Thus, the method 100 may in some examples comprise receiving a paging message in a PO in the second network. If the paging message comprises a paging message in the subset of paging messages, the UE may in some examples ignore the paging message. If the paging message comprises a paging message not in the subset of paging messages, the UE may respond to the paging message, for example by ending the service in the first network and transitioning to a connected state in the second network.

[0056] The subset of paging messages may comprise one of the following non-limiting examples:

[0057] • paging messages other than paging messages for voice calls;

[0058] • paging messages other than paging messages for one or more predetermined Protocol Data Unit, PDU, sessions; or paging messages other than paging messages for voice calls or one or more predetermined PDU sessions.

[0059] That is, in an example, the UE may indicate that it wishes to receive paging messages only for voice calls and no other paging messages.

[0060] The method 100 may in some examples comprise, after ending the service in the first network, sending a not busy indication to the second network. Thus, the UE may once again receive paging messages in the second network after the service in the first network has ended.

[0061] Figure 2 is a schematic of an example of an apparatus 200 in a User Equipment, UE, for sending a busy indication, wherein the UE is equipped with a plurality of Universal Subscriber Identity Modules, USIMs, including a first USIM associated with a first network and a second USIM associated with a second network. The apparatus 200 comprises processing circuitry 202 (e.g. one or more processors) and a memory 204 in communication with the processing circuitry 202. The memory 204 contains instructions, such as computer program code 410, executable by the processing circuitry 202. The apparatus 200 also comprises an interface 206 in communication with the processing circuitry 202. Although the interface 206, processing circuitry 202 and memory 204 are shown connected in series, these may alternatively be interconnected in any other way, for example via a bus.

[0062] In one embodiment, the memory 204 contains instructions executable by the processing circuitry 202 such that the apparatus 200 is operable / configured to, if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, sending the busy indication to the second network. In some examples, the apparatus 200 is operable / configured to carry out the method 100 described above with reference to Figure 1.

[0063] Examples of this disclosure may include a computer program comprising instructions which, when executed on at least one processor (e.g. the processing circuitry 202 shown in Figure 2), cause the at least one processor to carry out a method according to this disclosure, such as for example the method 100 of Figure 1. Examples of this disclosure may also include a carrier containing the computer program. The carrier may comprise for example one of an electronic signal, optical signal, radio signal or computer readable storage medium. Examples of this disclosure may also include a computer program product comprising non transitory computer readable media having stored thereon the computer program. It should be noted that the above-mentioned examples illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative examples without departing from the scope of the appended statements. The word “comprising” does not exclude the presence of elements or steps other than those listed in a claim, “a” or “an” does not exclude a plurality, and a single processor or other unit may fulfil the functions of several units recited in the statements below. Where the terms, “first”, “second” etc. are used they are to be understood merely as labels for the convenient identification of a particular feature. In particular, they are not to be interpreted as describing the first or the second feature of a plurality of such features (i.e. , the first or second of such features to occur in time or space) unless explicitly stated otherwise. Steps in the methods disclosed herein may be carried out in any order unless expressly otherwise stated. Any reference signs in the statements shall not be construed so as to limit their scope.

Claims

Claims1 . A method in a User Equipment, UE, of sending a busy indication, wherein the UE is equipped with a plurality of Universal Subscriber Identity Modules, USIMs, including a first USIM associated with a first network and a second USIM associated with a second network, the method comprising: if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, sending the busy indication to the second network.

2. The method of claim 1 , where in the second time period for sending the busy indication to the second network comprises one or more of: a time period for switching the UE from the first network to the second network; a time period for establishing a Radio Resource Control (RRC) connection in the second network; a time period for transmitting the busy indication in the second network; a time period for returning to RRC inactive or idle mode in the second network; and / or a time period for switching the UE from the second network to the first network.

3. The method of claim 1 or 2, comprising receiving a paging message in the second network before determining that the UE will establish the service in the first network.

4. The method of claim 3, comprising ignoring the paging message.

5. The method of claim 3 or 4, wherein sending the busy indication to the second network comprises sending a reject paging indication to the second network.

6. The method of any of claims 1 to 5, wherein the UE is configured with a plurality of Multiple USIM, MUSIM, gaps in the first network, and the UE is configured with one or more paging occasions, PCs, in the second network in one or more of the MUSIM gaps.

7. The method of claim 6, comprising, after determining that the UE will establish the service in the first network, sending an indication to the first network that no MUSIM gaps are preferred by the UE in the first network.

8. The method of claim 7, comprising, after ending the service in the first network, sending an indication to the first network that MllSIM gaps are preferred by the UE in the first network.

9. The method of any of claims 1 to 8, wherein the busy indication indicates that all paging in the second network is restricted.

10. The method of any of claims 1 to 6, wherein the busy indication indicates that a subset of paging messages in the second network is restricted.

11. The method of claim 10 when dependent on claim 2, comprising receiving a paging message in one of the one or more POs in the second network.

12. The method of claim 11 , comprising: if the paging message comprises a paging message in the subset of paging messages, ignoring the paging message; and if the paging message comprises a paging message not in the subset of paging messages, responding to the paging message.

13. The method of any of claims 10 to 12, wherein the subset of paging messages comprises: paging messages other than paging messages for voice calls; paging messages other than paging messages for one or more predetermined Protocol Data Unit, PDU, sessions; or paging messages other than paging messages for voice calls or one or more predetermined PDU sessions.

14. The method of any of claims 1 to 13, comprising, after ending the service in the first network, sending a not busy indication to the second network.

15. The method of any of claims 1 to 14, wherein the service comprises a voice call, video call, critical service, Ultra Reliable Low Latency, URLLC, service, real time service, software update of the UE in the first network, and / or one or more measurements in the first network.

16. The method of any of claims 1 to 14, comprising determining that the UE will transition to a connected state in the first network at the first time instant.

17. The method of any of claims 1 to 16, wherein the first network is the same as the second network.

18. The method of any of claims 1 to 16, wherein the first network is different to the second network.

19. The method of any of claims 1 to 18, wherein: the first network comprises a second Public Land Mobile Network, PLMN, or a second Non Public Network, NPN; and / or the second network comprises a second PLMN or a second NPN.

20. The method of any of claims 1 to 19, wherein sending the busy indication to the second network comprises transitioning to a connected state in the second network, sending the busy indication to the second network, and transitioning to an idle state in the second network.

21. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out a method according to any of claims 1 to 20.

22. A carrier containing a computer program according to claim 21 , wherein the carrier comprises one of an electronic signal, optical signal, radio signal or computer readable storage medium.

23. A computer program product comprising non transitory computer readable media having stored thereon a computer program according to claim 21.

24. Apparatus in a User Equipment, UE, for sending a busy indication, wherein the UE is equipped with a plurality of Universal Subscriber Identity Modules, USIMs, including a first USIM associated with a first network and a second USIM associated with a second network, the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to: if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, send the busy indication to the second network.

25. The apparatus of claim 24, wherein the memory contains instructions executable by the processor such that the apparatus is operable to perform the method of any of claims 2 to 20.

26. Apparatus in a User Equipment, UE, for sending a busy indication, wherein the UE is equipped with a plurality of Universal Subscriber Identity Modules, USIMs, including a first USIM associated with a first network and a second USIM associated with a second network, the apparatus comprising a processor and a memory, the memory containing instructions executable by the processor such that the apparatus is operable to: if a first time period until a first time instant, when the UE will establish a service in the first network, is at least as long as a second time period for sending a busy indication to the second network, send the busy indication to the second network.

27. The apparatus of claim 26, wherein the memory contains instructions executable by the processor such that the apparatus is operable to perform the method of any of claims 2 to 20.

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