Controlling rat access to a network for user equipment

Abstract

A user equipment, network control node and methods. The method performed on the user equipment comprises: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice of a RAT to use to request access to said PLMN.

Description

[0001] CONTROLLING RAT ACCESS TO A NETWORK FOR USER EQUIPMENT

[0002] TECHNOLOGICAL FIELD

[0003] Various example embodiments relate to wireless communication networks.

[0004] BACKGROUND

[0005] National roaming services are required to provide seamless connectivity for mobile user equipment, particularly in areas where the primary network operator lacks coverage. Network operators may provide access to the network using multiple different Radio Access Technologies (RATs), such as 4G and 5G

[0006] BRIEF SUMMARY

[0007] The scope of protection sought for various example embodiments of the invention is set out by the independent claims. The example embodiments 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 embodiments of the invention.

[0008] According to various, but not necessarily all, example embodiments of the invention there is provided an apparatus comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0009] Where restrictions to the use of certain network slices of certain RATs are to be imposed on particular apparatus, then providing congestion information regarding non-restricted alternative network slices allows an informed selection of an alternative network slice and thereby potentially reduces signalling and interruptions and furthermore, provides increased granularity in the provision of this relevant information.

[0010] 2 According to various, but not necessarily all example embodiments of the invention there is provided an apparatus, comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

[0011] According to various, but not necessarily all example embodiments of the invention there is provided a method performed at an apparatus, said method comprising: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice associated with a RAT to use to request access to said PLMN.

[0012] According to various, but not necessarily all example embodiments of the invention there is provided a method comprising: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

[0013] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

[0014] Where The apparatus feature is described as being operable to provide a function, it will be appreciated that this includes The apparatus feature which provides that function or which is adapted or configured to provide that function.

[0015] BRIEF DESCRIPTION

[0016] Some example embodiments will now be described with reference to the accompanying drawings in which: FIG. 1 illustrates a signalling diagram according to an example embodiment of the subject matter described herein;

[0017] Fig. 2 illustrates a signalling diagram according to a further example embodiment of the subject matter described herein;

[0018] Fig. 3 illustrates a user equipment and network entity according to an example embodiment of the subject matter described herein;

[0019] Fig.4 shows a flow diagram schematically illustrates steps in a method performed at a user equipment according to an example embodiment of the subject matter described herein;

[0020] Fig.5 shows a flow diagram schematically illustrates steps in a method performed at a network control node according to an example embodiment of the subject matter described herein;

[0021] Fig.6 shows a flow diagram schematically illustrates steps in a method performed at a user equipment according to a further example embodiment of the subject matter described herein; and

[0022] Fig.7 shows a flow diagram schematically illustrates steps in a method performed at a network control node according to a further example embodiment of the subject matter described herein.

[0023] DETAILED DESCRIPTION

[0024] Before discussing the example embodiments in any more detail, first an overview will be provided. In order to be able to provide consistent services to some users, restricting use of Radio Access Technologies (RAT) for other users such as national roamers in a visited public land mobile network VPLMN may be desirable to address quality of service concerns and network congestion concerns.

[0025] The application relates to restricting access to a network for a particular user equipment. Access may be restricted with a certain granularity and may take congestion into account when restricting or selecting a RAT, or a network slice associated with a RAT to use for connecting to a public land mobile network PLMN.

[0026] Embodiments provide congestion information for non-restricted RATs to a user equipment, such that the user equipment may use the congestion information when determining a RAT to use for connecting to a PLMN. In some example embodiments, congestion information for non-restricted network slices of nonrestricted RATs may be provided to a user equipment, such that the user equipment may use the congestion information when determining a network slice to use for connecting to a PLMN or to a RAT of a PLMN. The congestion information may comprise congestion load and congestion threshold value, the latter may be specific to particular UEs.

[0027] The restriction may be provided for certain UEs in certain locations for certain periods of time. For example, a network may provide RAT restriction information on a network slice granularity or on a RAT granularity for, for example, the duration of a soccer game. This allows the network to make the soccer game available to preferred UEs and to restrict it to other UEs either on certain network slices or on certain RATs. In other circumstances an operator may simply want to prioritise a certain group of users and hence limit usage for other users, The priority group of users may be higher subscription users or they may be local users on their home network HPLMN.

[0028] The restriction may be on time as in the example above, or it may be on congestion value or it may be on both.

[0029] Currently the only existing mechanisms to limit a UE's utilization of certain RATs employed by the network operators involves rejecting the UE's attach request tracking area update (TAU) request or a registration request with certain condition codes, such as condition code (CC) #15 or #27. Which are defined as follows:

[0030] • Cause #15 - No suitable cells in tracking area (TA)

[0031] 5 o This 5GMM cause is sent to the UE if it requests service, or if the network initiates a deregistration request, in a tracking area where the UE, by subscription, is not allowed to operate, but when it should find another allowed tracking area in the same PLMN or an equivalent PLMN or the same SNPN or an equivalent SNPN.

[0032] • Cause #27 - N1 mode not allowed o This 5GMM cause is sent to the UE if it requests service, or if the network initiates a deregistration request, in a PLMN or SNPN where the UE by subscription or operator policy, is not allowed to operate in N1 mode.

[0033] However, these cause codes simply indicate that the public land mobile network PLMN is restricted for the UE and there is no possibility of indication that the request has been rejected due to the RAT being restricted. This results in: a) increased signalling loads within the network; b) service outage until the UE selects another RAT that is not restricted; and c) UE keeping re-attempting without success on the same PLMN / RAT upon the UE re-enabling the corresponding RAT.

[0034] It would be desirable to address these drawbacks while maintaining the network operational requirements.

[0035] PLMN selection and roaming

[0036] The Mobile Station (MS) / UE normally operates on its home PLMN (HPLMN) or equivalent home PLMN (EHPLMN). However, a visited PLMN (VPLMN) may be selected, e.g., if the MS loses coverage. There are two modes for PLMN selection:

[0037] I) Automatic mode: This mode utilizes a list of PLMN / access technology combinations in priority order. The highest priority PLMN / access technology combination which is available and allowable is selected by the MS. ii) Manual mode: In this case the MS indicates to the user which PLMNs are available. Only when the user makes a manual selection the MS tries to obtain normal service on the VPLMN.

[0038] To inhibit repeated attempts to have roaming service on a not allowed area (i.e. Local Area (LA) or Tracking Area (TA)), when the MS is informed that an area is forbidden, the LA or TA is added to a list of "forbidden or restricted location areas for roaming" or "forbidden tracking areas for roaming" respectively

[0039] 6 which is stored in the MS. These lists, if existing, are deleted when the MS is switched off or when the SIM is removed, and periodically (with period in the range 12 to 24 hours). LA area restrictions may always be valid for complete location areas independent of possible subdivision into GPRS routing areas. The structure of the routing area identifier (see 3GPP TS 23.003 [22A]) supports area restriction on LA basis.

[0040] In order to indicate / trigger the change of the PLMN / RAT due to potential restrictions for an operator, the main operations and messages are the following:

[0041] • UE Registration (initial / MRU mobility registration update) procedure, and,

[0042] • UE configuration update (UCU).

[0043] UE Registration (initial / MRU) procedure:

[0044] A UE needs to register with the network to get authorized to receive services, to enable mobility tracking and to enable reachability. The UE initiates the Registration procedure using one of the following Registration types:

[0045] Initial Registration to the 5GS;

[0046] Mobility Registration Update upon changing to a new Tracking Area (TA) outside the UE's Registration Area in both CM-CONNECTED and CM-IDLE state, or various other reasons.

[0047] UE Configuration Update procedure (4.2.4.2 of TS 23.502):

[0048] This procedure is initiated by the AMF when the AMF wants to update access and mobility management related parameters in the UE configuration.

[0049] This procedure is also used to trigger UE to perform, based on network indication, either Mobility Registration Update procedure while the UE is in CM-CONNECTED state to modify non-access stratum (NAS) parameters that require negotiation (e.g. MICO mode) or to steer the UE towards EPC evolved packet core as specified in clause 5.31 .3 of TS 23.501 [2], or Mobility Registration Update procedure after the UE enters CM-IDLE state (e.g. for changes to Allowed Network Slice Selection Assistance Information (NSSAI) that require re-registration) or to update the UE with the Alternative single Network Slice Selection Assistance Information (S-NSSAI) . If a Registration procedure is needed, the AMF provides an indication to the UE to initiate a Registration procedure.

[0050] There are some methods that allow a network to restrict a UE to use a particular PLMN in a specific area(s), such as those described below: 1) Using the current3GPP concept (defined in 3GPP TS 23.122): to inhibit repeated attempts to have roaming service on a not allowed area (i.e. LA or TA), when the MS is informed that an area is forbidden, the LA or TA is added to a list of "forbidden location areas for roaming" or "forbidden tracking areas for roaming" respectively which is stored in the MS.

[0051] 2) According to current 3GPP specifications, when the UE from PLMN#A, either already attached in evolved packet system (EPS) of PLMN#B or not yet, selects and registers to the PLMN#B 5G Standalone (SA), according to the existing 3GPP specifications, PLMN#B can send a well-known reject cause code like #15 (No suitable cells in tracking area) or #27 (N1 mode not allowed) in the REGISTRATION REJECT message to prevent the UE from registering into its 5GS.

[0052] • Based on these cause codes (CCs), the UE will de-register from the PLMN where it has received the signalling and try to find a suitable one which leads to some interruption time due to the UE being deregistered and trying to connect again.

[0053] There are circumstances where a RAT restriction feature might be particularly useful such as if an operator wants to impose a RAT restriction on a certain number of (e.g., national roamer) UEs, i.e., UEs which are not originally its customers (national roaming), when there is, or it is expected a high load / congestion on the RAT.

[0054] Where it is desirable to restrict certain UEs to access a PLMN such as a HPLMN or VPLMN or a serving (or registered) PLMN using particular RATs, then it may be desirable to provide additional information to the UE such that it can select an alternative appropriate RAT. For example, were information on whether a RAT is restricted or not is provided then providing additional information about the congestion value / load of the non-restricted RATs may allow a UE to select an appropriate RAT. While, if there is no information about the congestion values of the non-restricted RATs, the UE might select a non-restricted RAT which is highly congested (but not restricted) which might lead to a further RAT restriction from the network in a short period of time.

[0055] Additionally, where network slicing is used for the RAT of the network then increased granularity on the restriction level may provide improved performance:

[0056] It may happen that a specific RAT is not restricted by the network (using the RAT utilization control Information Element (IE)), but certain network slices of the RAT may be restricted. For example, there may be a set of requested S-NSSAIs (Single Network Slice Selection Assistance Information, providing a unique

[0057] 8 identifier for the slice) selected by the UE, and one or more S-NSSAIs of the RAT may be congested, and the network would like to restrict those slices for the UE. In case that the UE includes any of the S-NSSAIs in the Requested NSSAI list when performing registration request procedure with the network for those slices, then the network would reject the registration of the UE for that slice which would result in waste of resources and signalling.

[0058] It may be that information is provided to the UE with respect to the RAT restriction, whereby the UE can select another RAT that is not restricted. In other words, the reject cause that the UE receives is directly tied to the RAT. However, in case all the network slices associate with a RAT are congested, then there is no way of connecting to the RAT using network slicing. In such a case, if the UE continues the operation on that RAT that contains congested network slices it may end up with degraded service or no service at all. A mechanism that allows an indication to be provided to the UE regarding such circumstances could improve service and decrease signalling overhead between the network and the UE.

[0059] Various example embodiments are outlined below:

[0060] UE:

[0061] - sends Initial Registration request message to register to PLMN_A. The UE may send the list of preferred RATs (or non-preferred RATs) per each PLMN in the request message.

[0062] - UE receives Registration accept message containing the RAT utilization control information element and per each RAT and / or slice of the RAT a congestion threshold value and / or a congestion load value for the RAT and / or slice of the RAT from the network is received

[0063] - The UE compares the existing congestion load value with the congestion threshold value for the specific RAT and / or slice of the RAT and considers the RAT and / or the slice of the RAT as restricted if the current congestion load value is higher or equal to the congestion threshold value received by the network.

[0064] - The UE selects a new RAT and / or slice of the RAT that is not restricted and / or congested.

[0065] - If the UE receives a congestion load higher than the congestion threshold information for at least K (pre-configured) number of slices of a RAT, then UE considers the RAT (providing the slices) restricted and shall initiate MRU mobility registration update procedure to change the RAT. Alternatively, UE may also initiate De-registration procedure to change PLMN.

[0066] - If there is suggested information provided by the network, UE shall connect to the network suggested RAT / Slice.

[0067] 9 • The UE stores the information about RAT restriction in its memory.

[0068] • The UE uses this information (e.g., pass the information to lower layers) to select an appropriate RAT / slice.

[0069] UE sends REGISTRATION Complete message including an acknowledgement flag along with selected RAT / Slice information in the message.

[0070] Network control node, AMF / MME / 6G-AMF:

[0071] - performs authentication, authorization and subscription validation check.

[0072] - determines to use RAT restriction for the UE.

[0073] - sends the RAT Utilization Control information list in the REGISTRATION ACCEPT message with the following details

[0074] RAT restriction list: Which RATs are restricted and which RATs are non-restricted containing the new elements: o Congestion load per each non-restricted RAT(s) o Congestion threshold value per each non-restricted RAT(s) o List of restricted / non-restricted slices per each non-restricted RAT(s) o Congestion load per each non-restricted slice per non-restricted RAT(s) o Congestion threshold level per each non-restricted slice per non-restricted RAT(s) o Timer information, e.g., availability timer for each restricted slice of the non-restricted RATs o Suggestion of alternate RAT / slice that is not restricted and less congested and in the UE's sent preferred RAT list o Timer for congestion information validity

[0075] - The network control node may send an updated value of the current congestion of the RAT and or of a slice of the RAT via a UE configuration update (UCU) message. o The network may send such information periodically to the UE or only when there is a big change (this can be pre-configured at network level) in the current congestion level value compared to the threshold.

[0076] - The network control node sends an updated RAT utilization control information in the Configuration Update Command to the UE. The UE can use MRU to change the RAT / slice accordingly.

[0077] In one example embodiment: a) The network (e.g., the AMF of the VPLMN or 6G AMF) sends congestion / load information (per RAT) for each of the non-restricted RATs within the RAT Utilization Control information IE.

[0078] Example scenario: RAT 1 : Unrestricted and congestion load value = 60%, RAT2: Unrestricted and congestion load value = 10%, RAT3: Restricted.

[0079] For automatic selection: the network (e.g., the AMF of the VPLMN or 6G-AMF) may set the RAT list in an increasing order of the congestion load value (e.g., high priority for low congested RAT). The UE stores this information, i.e., list of RATs with the associated congestion information, in its memory.

[0080] For manual PLMN / RAT selection: the UE / user can select a RAT (e.g., may not be the lowest congested RAT) as per its system requirements or based on its implementation.

[0081] As another option, the UE Non-Access Stratum (NAS) layer may send the preferred RAT list to be selected to lower UE layer (i.e., UE Access Stratum (AS) layer. This can help AS layer during cell selection / re-selection.

[0082] As another option, the network (e.g., the AMF of the VPLMN or 6GMM or AMF) might also include the congestion / load information (per RAT) for each of the restricted RATs within the RAT Utilization Control information IE. b) The network (e.g., AMF of VPLMN or 6GMM or AMF) sends a per-UE congestion threshold value for each of the non-restricted RATs. The network based on operator's decision can apply this information to have differential treatment to different type of UEs (e.g., HPLMN UEs vs. VPLMN UEs or priority UEs vs. non-priority UEs).

[0083] • Example scenario:

[0084] For UE1 (roamer UE / non-priority UE): RAT_1 : Unrestricted; congestion load = 60%, congestion threshold value = 50%, RAT_2: Unrestricted; congestion load = 10%, congestion threshold value = 50%, RAT_3: Restricted; congestion load = 80%, congestion threshold value = 70%.

[0085] For UE2 (priority UE): RAT_1 : Unrestricted; congestion load =60%, congestion threshold value= 100%, RAT2: Unrestricted; congestion load = 10%, congestion threshold value = 100%, RAT3: Restricted.

[0086] Each UE, based on the received information from the network, when the congestion load value is higher or equal to the congestion threshold value received, determines that the specific RAT is a restricted RAT for that PLMN.

[0087] As another option, the network might also include the congestion / load information (per RAT) for each of the restricted RATs within the RAT Utilization Control information IE.

[0088] 11 As another option the network may not send an explicit restricted indication, but may rely on the congestion load value being higher than the congestion threshold value to indicate this to the UE in an implicit way. c) The network at any point may send an updated value of the current congestion load or the congestion threshold value of the RAT and or a slice of the RAT via a UE configuration update (UCU) message.

[0089] • The network may send such information periodically to the UE or only when there is a change in the current congestion load value compared to the congestion threshold value that is higher than a preconfigured value or higher than a value left up to the network operator's decision.

[0090] Embodiment 2:

[0091] The network (e.g., AMF of VPLMN or 6GAMF) may send a slice restriction list for each of the non-restricted RAT(s) in the RAT Utilization.

[0092] • Example scenario per UE: o RAT 1 : RAT not restricted, specific slices restricted: S-NSSA1 1 (out of S-NSSAIs 1 ,2,3); o RAT2: RAT not restricted, specific slices restricted: None (out of S-NSSAIs 3,4,6); o RAT3: RAT restricted

[0093] • In order to decide at the network level whether a specific slice is restricted (in addition to potential RAT restriction.

[0094] Embodiment 2a: As a dependent example following the same principle as in the previous examples, the congestion load and congestion threshold value, e.g., number of users or traffic load, per non-restricted slice / S-NSSAI can be provided by the network to the UE. UE may use such information in such a way that if a S-NSSAI that the UE wants to use from a certain RAT that is not restricted, is above a certain congestion load value compared to the congestion threshold value, then the UE does not include that slice in the Requested NSSAI towards the network to avoid a later rejection from the network. Thus, reducing signalling waste between the network and the UE.

[0095] In a further example, following the same principle as in previous examples, timer information per restricted slice per RAT, e.g., time after which slice shall become unrestricted again for the UE for a RAT, can be provided by the network to the UE. Additionally time information regarding the validity of the congestion information may be provided and when the timer expires the store congestion information may be updated to default values, which may be configured at the UE or by the network.

[0096] The network (e.g., the AMF of the VPLMN) sends to the UE congestion level information of S-NSSAIs associated with a RAT together with the threshold for each S-NSSAI of the RAT and / or the S-NSSAIs that are restricted for the RAT.

[0097] • When the UE determines that K number of S-NSSAIs (configurable by the network) associated with the RAT are restricted / congested (e.g., congestion load above congestion threshold value) then the RAT itself is considered as congested by the UE in an implicit way and the UE shall change to a different RAT.

[0098] For relevant examples, the congestion measurement criteria by the network, can be defined in terms of, e.g., number of UEs or traffic load, etc., in a specific RAT / Slice.

[0099] Fig. 1 shows a signalling diagram illustrating signalling between a UE and network control node, via a network node according to an embodiment.

[0100] Step 1 : UE 410, in the visited PLMN (can be valid for home PLMN), sends Initial Registration request to register in PLMN_A. The UE may send the list of preferred RATs (and / or non-preferred RATs) per each PLMN in the request message.

[0101] Step 2: AMF / MME / 6G-AMF (termed 6GMM in fig.) performs authentication, authorization and subscription validation check.

[0102] Step 3: AMF / MME / 6G-AMF 420 determines to use RAT restriction for the UE. Hence AMF / MME / 6G-AMF sends the RAT Utilization Control information list in the REGISTRATION ACCEPT message with at least some of the following details

[0103] 1 . RAT restriction list: Which RATs are restricted and which RATs are non-restricted

[0104] 2. Congestion information per each non-restricted RAT(s)

[0105] 3. Congestion threshold information per each non-restricted RAT(s)

[0106] 4. List of restricted / non-restricted slices per each non-restricted RAT(s)

[0107] 5. Congestion information per each non-restricted slice per non-restricted RAT(s)

[0108] 6. Congestion threshold information per each non-restricted slice per non-restricted RAT(s)

[0109] 7. Timer information, e.g., availability timer for each restricted slice of the non-restricted RATs 8. Suggestion of alternative RAT / slice that is not restricted and less congested and in the UE's sent preferred RAT list.

[0110] 9. Timer for congestion validity

[0111] Although the sending of this information is shown here as part of the UE registration procedure to the PLMN, the AMF / MME / 6G-AMF can also send much of this information in an updated RAT utilization control information in a Configuration Update Command message to the UE when it is already registered to a PLMN. Where the updated information indicates a change of RAT may be required / desirable, the UE can use MRU procedure to change the RAT / slice accordingly. The UE will also update stored restriction and congestion information for different RATs and network slices.

[0112] Step 4: The UE stores the information about RAT restriction in its memory. The UE uses this information (e.g., passes the information to lower layers UE AS) to select an appropriate RAT / slice.

[0113] • The UE receives per each RAT and / or slice of the RAT a congestion threshold value and / or a congestion load value for the RAT and / or slice of the RAT

[0114] • The UE compares the existing congestion load value with the congestion threshold value for the specific RAT and / or slice of the RAT and considers the RAT and / or the slice of the RAT as restricted if the current congestion load value is higher or equal to the congestion threshold value received for the specific RAT or slice currently used to connect to the PLMN.

[0115] In that case UE selects a new RAT and / or slice of the RAT.

[0116] • If the UE receives a congestion load value higher than the congestion threshold value for at least K (pre-configured) number of slices, then UE considers the RAT (providing the slices) is restricted and initiates MRU to change the RAT. Alternatively, UE may also initiate De-registration to change PLMN.

[0117] • If there is suggested info by the network, UE shall connect to the network using suggested RAT / Slice.

[0118] • The network at any point may send an updated value of the current congestion of the RAT and or a slice of the RAT via a UE configuration update (UCU) message. o The network may send such information periodically to the UE or only when there is a big change (this can be pre-configured at network level) in the current congestion load compared to the congestion threshold value.

[0119] Step 5: UE sends REGISTRATION ACCEPT message. The UE includes an acknowledgement flag along with selected RAT / Slice information in the message. Fig. 2 shows a signalling diagram between a user equipment 410 and a network control node 420 according to a further embodiment. At step 10 the UE 410 is connected to the network and has received and stored RAT utilisation control information comprising a list of restricted and non-restricted RATs and in some cases a list of restricted and non-restricted network slices of these RATs. It also contains congestion threshold information and congestion level information for at least some of the non-restricted RATs and in some cases the non-restricted network slices.

[0120] The network control node 420 at step 20 determines that there has been an operational change and the congestion threshold information and congestion level information for at least some of the restricted RATs should be updated. It therefore generates and then transmits at 30 a UE configuration update message. This configuration update message contains RAT utilisation control information which includes a list of restricted and non-restricted RATs and / or network slices and additionally updated congestion threshold information and congestion level information for at least some of the non-restricted RATs and / or network slices. The UE receives this and then at 40 where the updated information indicates that a change of RAT may be desirable, that is the current RAT or network slice has a congestion level above the congestion threshold and therefore should be marked as restricted, which then makes UE select a new RAT or network slice in dependence upon the congestion information and perform a mobility registration update with the network to connect via that RAT or network slice to the to the PLMN.

[0121] Fig. 3 shows a network control node / entity 420 which may be configured to perform the method steps shown in Fig. 5 or 7. The network control node 420 comprises at least one memory 422 which may store instructions executable by at least one processor 421 of the network control node 420. The network control node 420 may comprise a transceiver 423 for transmission and reception of signals. The network control node may refer to at least one of the following non-limiting examples: an AMF, a MME or a 6GAMF. The network control node 430 communicates with the user equipment 410 via a network node 430.

[0122] Fig. 3 further shows a user equipment 410 configured to perform the method steps shown in Fig. 4 or 6. The user equipment 410 comprises at least one memory 412 which may store instructions executable by at least one processor 411 of the user equipment 410. The user equipment 410 may comprise a transceiver 413 for transmission and reception of radio signals. The user equipment 410 may comprise a timer 414 . The user equipment refers to any mobile end or terminal device that may be capable of wireless communication. By way of example rather than limitation, user equipment UE may also be referred to as a communication device, a terminal device, a Mobile Station (MS). The user equipment may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable terminal device, a personal digital assistant (PDA) , vehicle-mounted wireless terminal devices, smart devices etc.

[0123] Fig. 4 schematically shows a flow diagram illustrating steps in a method performed at a user equipment according to an embodiment. In a first step S10 the user equipment receives a message that contains an indication of multiple RATs for a PLMN, an indication as to whether they are restricted or not and congestion information. At step S20 the user equipment stores the restriction indication(s) and the congestion information. At step S30 the user equipment compares the congestion load value and the congestion threshold value for a non-restricted RAT and at D5 it determines if the congestion load value is greater than the congestion threshold value. If it is then it marks the RAT as restricted at S40 and at D15 determines if there is a further non-restricted RAT. If there is not then it proceeds to step S50 and when a new connection to the PLMN is required the user equipment will select a non-restricted RAT with a low congestion load. This may be where the UE had requested registration and the message is a registration accept message, or it may be where the message is received while the UE is connected to the network and the message is a configuration update message indicating for example that the current network slice associated with a RAT has become congested or that the current RAT has become restricted and is therefore now deemed to be restricted.

[0124] Fig. 5 schematically shows steps in a method performed at a network control node according to an embodiment. In a first step S100 the network control node determines that at least one RAT is restricted for a particular user equipment. It then generates at step S110 a message that indicates the RAT to be restricted, and this message comprises further information regarding other RATs and where they are nonrestricted, RAT's congestion information for them. At step S120 the network control node transmits the message to the UE. It should be noted that the indication as to whether the RAT is restricted or not may be an explicit indication or it may be implicit in that it may simply be that the congestion information indicates that a congestion load is greater than a congestion threshold value that is set for that particular UE. Where this is the case this is an implicit indication that the RAT is restricted for that UE and the UE will behave accordingly and not try to select that RAT for connection to the PLMN.

[0125] Fig. 6 shows steps performed at a user equipment according to a further embodiment. In this embodiment, at least some of the RATs available for connecting to the PLMN can be accessed via network slices. In a first step S200 the UE receives a message that contains an indication of multiple RATs and multiple network slices for at least one of the RATs that are supported for connecting to the PLMN. It also comprises an indication that at least one of the network slices is restricted and congestion information for the non-restricted network slices and in some cases for any non-restricted RAT(s) that do not have network slices. At step S210 the UE stores the restriction indication(s) and congestion information for the RATs and network slices. At step S220 the UE compares the congestion load and congestion threshold values for non-restricted network slices of a RAT. At step D35 it determines if the congestion load is greater than the congestion threshold value for the network slice that is currently marked as non-restricted and if it is, it proceeds to step S230 where it marks the network slice as restricted and updates this in the stored restriction information.

[0126] The UE then proceeds to perform step D45 where it is determined whether there is another non-restricted network slice. If there is then it proceeds to consider whether the congestion load is greater than the congestion threshold for this network slice. If there isn't then the UE proceeds to D55 where it determines if there are more than a predetermined number of network slices for this RAT that are marked as restricted. If there are then it proceeds to step S240 and marks the RAT as restricted. This provides an indication that all the network slices of this RAT should also be considered to be restricted. D65 is then performed to determine if there is another non-restricted RAT and if not the UE proceeds to step 250. If at D55 it is determined that there are fewer than a predetermined number of network slices that are marked as restricted then the UE proceeds to D65 to determine if there is another non-restricted RAT to be considered.

[0127] If at step D65 it determines that there is another non-restricted RAT then it determines if this has network slices at D75 and if it does it proceeds back to step D35. If the non-restricted RATs does not have network slices then it proceeds to step S240 to determine whether the RAT should be considered restricted or not based on its congestion load and congestion threshold value. The UE will then determine if there is another non-restricted RAT to consider.

[0128] Once all the non-restricted RATs have been considered the UE will perform step S250 and where a new connection is requested will select one of the non-restricted RATs or network slices in dependence upon the congestion load. If there are no non-restricted RATs or network slices available then the UE may determine whether there is another PLMN that may be available and will look at the RATs and network slices for connecting to this PLMN by performing the method described above. If there is no alternative PLMN then the UE will de-register from the network and wait for a predetermined time until it tries again to determine. In this regard, in some example embodiments, the message received at step S200 may also

[0129] 17 have timer indications indicating a length of time for which the restriction information and congestion information is valid. Where this is the case then the UE may wait for this length of time before it tries again to connect to find a non-restricted network slice or RAT for connection to the PLMN. If there is no time information, then it may wait for a preconfigured time.

[0130] Fig. 7 schematically shows steps performed at a network control node according to an embodiment. At step S300 the network control node determines that at least one network slice or at least one RAT is restricted for a particular user equipment. The network control node may determine this due to changes in operational conditions, for example it may be that the PLMN is about to become congested due to a local event and is to restrict the use of certain network slices or RATs for a certain user equipment.

[0131] At step S310 the network control node generates a message indicating the network slice to be restricted. This may be in the form of a list of restricted network slices. In some cases there may also be an indication of restricted RATs. The message may further comprise information regarding other non-restricted network slices and congestion information for the non-restricted network slices.. The congestion information may comprise congestion threshold values and congestion load values. It may also contain information about different RATs and the network slices of these different RATs or just the RATs where they may not support network slicing. At step S320 the network control node transmits the message towards the UE.

[0132] ********************

[0133] According to various, but not necessarily all, example embodiments of the invention there is provided an apparatus, comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: receiving a message comprising an indication of multiple radio access technologies RATs that are provided for accessing a public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs that are not restricted; and selecting a non-restricted RAT to use to request access to said PLMN in dependence upon said congestion information.

[0134] Where restrictions to the use of certain RATs are to be imposed on particular apparatus, then providing congestion information regarding non-restricted alternative RATs allows an informed selection of an alternative RAT and thereby potentially reduces signalling and interruptions. In some example embodiments, said congestion information comprises a congestion load value.

[0135] In some example embodiments, said congestion information further comprises a congestion threshold value.

[0136] In some example embodiments, said at least one restriction indication for said apparatus comprises said congestion information, said congestion information comprising congestion load and corresponding congestion threshold values for at least some of said RATs, said congestion load value being greater than said corresponding congestion threshold value for said RAT being indicative of said RAT being restricted.

[0137] Although the indication as to whether the RATs are restricted for the apparatus or not may be an explicit restriction indication in some cases the indication comprises the congestion information, the apparatus determining whether the apparatus is restricted or not for that RAT by comparing the received congestion load value with the associated congestion threshold value and where it exceeds the congestion threshold value determining that the apparatus is restricted for that RAT.

[0138] In some example embodiments, said at least one restriction indication comprises an explicit restriction indication and said selecting comprises: comparing said congestion load values for the one or more of said RATs that are not explicitly indicated as being restricted with said corresponding congestion threshold values; determining said one or more RATs to be treated as a restricted RAT where said congestion load value is greater than said corresponding congestion threshold value; and selecting a non-restricted RAT.

[0139] In some example embodiments, the message comprises an explicit restriction indication for at least one RAT, the congestion information for other RATs not explicitly marked as non-restricted may also indicate that the associated RAT is restricted for that user equipment where the congestion load value is greater than the congestion threshold value. The apparatus is configured not to select a RAT that is explicitly marked as restricted or one that it determines to be restricted from the congestion information.

[0140] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: storing said at least one of said restriction indication; and in response to receiving updated congestion information, comparing said received congestion load value with a corresponding congestion threshold value and when said compared values indicate one of

[0141] 19 said RATs to have changed to a restricted or non-restricted state, updating a corresponding stored restriction indication for said RAT.

[0142] The received restriction information may be stored by the apparatus and where updated information is received which indicates that a previously stored restriction may no longer be valid then the apparatus may be configured to update the stored restriction information.

[0143] When selecting a RAT to use for connection to a PLMN then the apparatus may select a RAT that is indicated as being not restricted and it may retrieve this information from the stored information which may comprise a list of RATs to restricted and in some cases a list of RATs that are not restricted.

[0144] In some example embodiments, said congestion information is received in a UE configuration update message.

[0145] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: in response to receiving updated congestion information for a RAT used for an registered connection, comparing said received congestion load value with a corresponding congestion threshold value and when said compared values indicate a change to a restricted state, selecting one of said non-restricted RATs by performing a mobility registration update

[0146] Where updated congestion information is received perhaps in a UE configuration update message then it may be that the currently used RAT for connection to the PLMN is now indicated as being restricted and in such a case, the apparatus may be configured to perform a mobility registration update and disconnect from the current RAT and select and connect to a new RAT. The new RAT may be selected from the list of unrestricted RATs and is selected based on the congestion information received for the RATs by the network.

[0147] In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which at least one of said RATs are restricted, the instructions, when executed by the at least one processor, further cause said apparatus to perform: updating at least one timer associated with said at least one of said RATs based on a respective one of said at least one time periods; and inhibiting selecting said at least one of said restricted RATs during said respective one of said at least one time periods. The restriction indication indicating restriction of a RAT may come with a time period which is indicative of how long the restriction is valid for and the apparatus may be configured to inhibit or prevent selecting the RAT during this period. The apparatus may also be configured to update the store of restricted RATs on expiry of the time period with the updated information.

[0148] In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which said congestion information for said non-restricted RAT is deemed to be valid, wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: resetting a timer with said time period and on expiry of said timer, updating said congestion information.

[0149] The congestion information may be updated after a predetermined time when it is no longer deemed to be valid. It may be updated to a default congestion load value and / or congestion threshold value and this may be a default value that is configured in the user equipment either on connection to the PLMN or on startup of the UE. Alternatively it may be a value received from the network.

[0150] In some example embodiments, said message comprises a RAT utilisation control information element, said RAT utilisation control element information element comprising said indications.

[0151] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: generating a registration request, said registration request including an indication of preferred RATs for each PLMN; and transmitting said registration request to said network.

[0152] The apparatus may transmit an indication of one or more preferred RATs for each PLMN when it transmits its registration request to the network.

[0153] In some example embodiments, said message comprises one of the following: a registration accept message, a configuration update or a deregistration message In some example embodiments, said apparatus is further caused to transmit an indication of said selected non-restricted RAT to said network in a registration complete message.

[0154] In some example embodiments, wherein said message further comprises an indication of multiple radio access technologies RATs that are provided for accessing at least one further public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs for said further PLMN that are not restricted; and wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: selecting a non-restricted RAT to use to request access to said PLMN or one of said at least one further PLMN in dependence upon said congestion information.

[0155] In addition to containing information regarding a current or serving PLMN and RATs associated with it, in some cases the message may contain information regarding other PLMNs and associated RATs along with restriction and congestion information. This allows the apparatus to select a non-restricted RAT to request access to other the registered or serving PLMN, or another non-restricted PLMN.

[0156] According to various, but not necessarily all example embodiments of the invention there is provided an apparatus, comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: determining that at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least some user equipment; generating a message comprising a restriction indication indicating that said at least one radio access technology RAT is restricted for said user equipment, said message further comprising information regarding RATs that are supported by said PLMN and are not restricted for said user equipment and congestion information for said RATs, at least some of said congestion information being for said RATs that are not restricted; and transmitting said message to said user equipment.

[0157] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining that at least one radio access technology RAT for accessing at least one further public land mobile network PLMN is to be restricted for at least some user equipment; and generating said message to further comprise an indication of multiple radio access technologies RATs that are provided for accessing at least one further public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs for said further PLMN that are not restricted.

[0158] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining at least one time period during which at least one of said RATs are restricted; and including an indication of said at least one time period in said message.

[0159] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining at least one time period during which said congestion information is deemed to be valid; and including said time period in said message.

[0160] In some example embodiments, said message comprises one of: a registration accept message, a configuration update or a deregistration message.

[0161] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: generating a configuration update message indication comprising updated configuration information for said user equipment; and transmitting said configuration update message to said user equipment.

[0162] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: receiving a registration request, said registration request including an indication of preferred RATs for at least one PLMN for a user equipment, said apparatus being further caused to perform: determining whether said at least one preferred RAT is restricted or not; selecting one of said at least one preferred RATs in dependence upon a determination that said

[0163] RAT is not restricted and has a low congestion load; and including an indication of said selected RAT as a preferred non-restricted RAT within said message. In some example embodiments said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load value being greater than said congestion threshold value for said user equipment being indicative of said RAT being restricted.

[0164] The processor, memory, and example algorithms, encoded as instructions, program, or code, may be the means for providing or causing the performance of the operation.

[0165] According to various, but not necessarily all, example embodiments of the invention there is provided an apparatus, comprising: means for receiving a message comprising an indication of multiple radio access technologies RATs that are provided for accessing a public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs that are not restricted; and means for selecting a non-restricted RAT to use to request access to said PLMN in dependence upon said congestion information.

[0166] According to various, but not necessarily all example embodiments of the invention there is provided the apparatus, comprising: means for determining that at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least some user equipment; means for generating a message comprising a restriction indication indicating that said at least one radio access technology RAT is restricted for said user equipment, said message further comprising information regarding RATs that are supported by said PLMN and are not restricted for said user equipment and congestion information for said RATs, at least some of said congestion information being for said RATs that are not restricted; and means for transmitting said message to said user equipment.

[0167] The means may perform the optional features set out in relation to the apparatus mentioned above.

[0168] According to various, but not necessarily all, example embodiments of the invention there is provided an apparatus, comprising: circuitry configured for receiving a message comprising an indication of multiple radio access technologies RATs that are provided for accessing a public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs that are not restricted; and circuitry configured for selecting a non-restricted RAT to use to request access to said PLMN in dependence upon said congestion information.

[0169] According to various, but not necessarily all example embodiments of the invention there is provided the apparatus, comprising: circuitry configured for determining that at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least some user equipment; circuitry configured for generating a message comprising a restriction indication indicating that said at least one radio access technology RAT is restricted for said user equipment, said message further comprising information regarding RATs that are supported by said PLMN and are not restricted for said user equipment and congestion information for said RATs, at least some of said congestion information being for said RATs that are not restricted; and circuitry configured for transmitting said message to said user equipment.

[0170] The circuitry may be configured perform the optional features set out in relation to the apparatus mentioned above.

[0171] According to various, but not necessarily all, example embodiments of the invention there is provided a method performed at an apparatus, the method comprising: receiving a message comprising an indication of multiple radio access technologies RATs that are provided for accessing a public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs that are not restricted; and selecting a non-restricted RAT to use to request access to said PLMN in dependence upon said congestion information.

[0172] In some example embodiments, said congestion information comprises a congestion load value.

[0173] In some example embodiments, said congestion information further comprises a congestion threshold value.

[0174] In some example embodiments, said at least one restriction indication for said apparatus comprises said congestion information, said congestion information comprising congestion load and corresponding congestion threshold values for at least some of said RATs, said congestion load value being greater than said corresponding congestion threshold value for said RAT being indicative of said RAT being restricted. In some example embodiments, said at least one restriction indication comprises an explicit restriction indication and said selecting comprises: comparing said congestion load values for the one or more of said RATs that are not explicitly indicated as being restricted with said corresponding congestion threshold values; determining said one or more RATs to be treated as a restricted RAT where said congestion load value is greater than said corresponding congestion threshold value; and selecting a non-restricted RAT.

[0175] In some example embodiments, the message comprises an explicit restriction indication for at least one RAT, the congestion information for other RATs not explicitly marked as non-restricted may also indicate that the associated RAT is restricted for that user equipment where the congestion load value is greater than the congestion threshold value. The method comprises not selecting a RAT that is explicitly marked as restricted or one that it determines to be restricted from the congestion information.

[0176] In some example embodiments, the method further comprises: storing said at least one of said restriction indication; and in response to receiving updated congestion information, comparing said received congestion load value with a corresponding congestion threshold value and when said compared values indicate one of said RATs to have changed to a restricted or non-restricted state, updating a corresponding stored restriction indication for said RAT.

[0177] In some example embodiments, said congestion information is received in a UE configuration update message.

[0178] In some example embodiments, the method further comprises: in response to receiving updated congestion information for a RAT used for an registered connection, comparing said received congestion load value with a corresponding congestion threshold value and when said compared values indicate a change to a restricted state, selecting one of said non-restricted RATs by performing a mobility registration update

[0179] In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which at least one of said RATs are restricted, the method further comprising: updating at least one timer associated with said at least one of said RATs based on a respective one of said at least one time periods; and inhibiting selecting said at least one of said restricted RATs during said respective one of said at least one time periods. In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which said congestion information for said non-restricted RAT is deemed to be valid, wherein the method further comprises: resetting a timer with said time period and on expiry of said timer, updating said congestion information.

[0180] In some example embodiments, said message comprises a RAT utilisation control information element, said RAT utilisation control element information element comprising said indications.

[0181] In some example embodiments, the method further comprises: generating a registration request, said registration request including an indication of preferred RATs for each PLMN; and transmitting said registration request to said network.

[0182] In some example embodiments, said message comprises one of the following: a registration accept message, a configuration update or a deregistration message

[0183] In some example embodiments, the method further comprises transmitting an indication of said selected non-restricted RAT to said network in a registration complete message.

[0184] In some example embodiments, wherein said message further comprises an indication of multiple radio access technologies RATs that are provided for accessing at least one further public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs for said further PLMN that are not restricted; and wherein the method further comprises: selecting a non-restricted RAT to use to request access to said PLMN or one of said at least one further PLMN in dependence upon said congestion information.

[0185] According to various, but not necessarily all example embodiments of the invention there is provided a method comprising: determining that at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least some user equipment; generating a message comprising a restriction indication indicating that said at least one radio access technology RAT is restricted for said user equipment, said message further comprising information regarding RATs that are supported by said PLMN and are not restricted for said user equipment and congestion information for said RATs, at least some of said congestion information being for said RATs that are not restricted; and transmitting said message to said user equipment.

[0186] In some example embodiments, the method further comprises: determining that at least one radio access technology RAT for accessing at least one further public land mobile network PLMN is to be restricted for at least some user equipment; and generating said message to further comprise an indication of multiple radio access technologies RATs that are provided for accessing at least one further public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs for said further PLMN that are not restricted.

[0187] In some example embodiments, the method further comprises: determining at least one time period during which at least one of said RATs are restricted; and including an indication of said at least one time period in said message.

[0188] In some example embodiments, the method further comprises: determining at least one time period during which said congestion information is deemed to be valid; and including said time period in said message.

[0189] In some example embodiments, said message comprises one of: a registration accept message, a configuration update or a deregistration message.

[0190] In some example embodiments, the method further comprises: generating a configuration update message indication comprising updated configuration information for said user equipment; and transmitting said configuration update message to said user equipment.

[0191] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: receiving a registration request, said registration request including an indication of preferred RATs for at least one PLMN for a user equipment, said apparatus being further caused to perform: determining whether said at least one preferred RAT is restricted or not; selecting one of said at least one preferred RATs in dependence upon a determination that said RAT is not restricted and has a low congestion load; and including an indication of said selected RAT as a preferred non-restricted RAT within said message.

[0192] In some example embodiments said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load value being greater than said congestion threshold value for said user equipment being indicative of said RAT being restricted.

[0193] According to various, but not necessarily all, example embodiments of the invention there is provided a computer program comprising instructions which, when executed by the apparatus, cause the apparatus to perform: receiving a message comprising an indication of multiple radio access technologies RATs that are provided for accessing a public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs that are not restricted; and selecting a non-restricted RAT to use to request access to said PLMN in dependence upon said congestion information.

[0194] According to various, but not necessarily all example embodiments of the invention there is provided a computer program comprising instructions which, when executed by the apparatus, cause the apparatus to perform: determining that at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least some user equipment; generating a message comprising a restriction indication indicating that said at least one radio access technology RAT is restricted for said user equipment, said message further comprising information regarding RATs that are supported by said PLMN and are not restricted for said user equipment and congestion information for said RATs, at least some of said congestion information being for said RATs that are not restricted; and transmitting said message to said user equipment.

[0195] According to various, but not necessarily all, example embodiments of the invention there is provided a computer program for performing the following: receiving a message comprising an indication of multiple radio access technologies RATs that are provided for accessing a public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs that are not restricted; and selecting a non-restricted RAT to use to request access to said PLMN in dependence upon said congestion information.

[0196] According to various, but not necessarily all example embodiments of the invention there is provided a computer program for performing the following: determining that at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least some user equipment; generating a message comprising a restriction indication indicating that said at least one radio access technology RAT is restricted for said user equipment, said message further comprising information regarding RATs that are supported by said PLMN and are not restricted for said user equipment and congestion information for said RATs, at least some of said congestion information being for said RATs that are not restricted; and transmitting said message to said user equipment.

[0197] According to various, but not necessarily all, example embodiments of the invention there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: receiving a message comprising an indication of multiple radio access technologies RATs that are provided for accessing a public land mobile network PLMN and at least one restriction indication indicating whether said RATs are restricted for said apparatus, said message further comprising congestion information, at least some of said congestion information being for said RATs that are not restricted; and selecting a non-restricted RAT to use to request access to said PLMN in dependence upon said congestion information.

[0198] According to various, but not necessarily all example embodiments of the invention there is provided a non- transitory computer readable medium comprising program instructions stored thereon for performing at least the following: determining that at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least some user equipment; generating a message comprising a restriction indication indicating that said at least one radio access technology RAT is restricted for said user equipment, said message further comprising information regarding RATs that are supported by said PLMN and are not restricted for said user equipment and congestion information for said RATs, at least some of said congestion information being for said RATs that are not restricted; and transmitting said message to said user equipment.

[0199] The instructions of the computer programs above may be for performing the optional features set out in relation to the method mentioned above.

[0200] 30 According to various, but not necessarily all, example embodiments of the invention there is provided an apparatus comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0201] Where restrictions to the use of certain network slices of certain RATs are to be imposed on particular apparatus, then providing congestion information regarding non-restricted alternative network slices allows an informed selection of an alternative network slice associated with a RAT and thereby potentially reduces signalling and interruptions and, provides increased granularity in the provision of this relevant information, allowing congestion to be managed on a network slice as well as a RAT basis.

[0202] In some example embodiments, said message further comprises at least one restriction indication and congestion information for at least one non-restricted RAT, the instructions, when executed by the at least one processor, further causing said apparatus to perform: selecting one of: said non-restricted RAT or nonrestricted network slice associated with a RAT to use to request access to said PLMN in dependence upon said congestion information for said non-restricted network slice associated with a RAT or said nonrestricted RAT.

[0203] In some example embodiments, said congestion information comprises a congestion load value.

[0204] In some example embodiments, said congestion information further comprises a congestion threshold value.

[0205] In some example embodiments, said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load being greater than said congestion threshold value being indicative of a restriction for the network slice associated with the RAT.

[0206] In some example embodiments, said at least one restriction indication comprises an explicit restriction indication and said selecting comprises: comparing said congestion loads for the one or more of said network slices that are not explicitly indicated as being restricted with said corresponding congestion threshold values; determining a corresponding network slice to be restricted where said congestion load is greater than said threshold value; and selecting said non-restricted network slice.

[0207] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: storing at least some of said at least one restriction indication; and in response to receiving updated congestion information, comparing said received congestion load with a corresponding congestion threshold value and where said compared values indicate a change to a restricted or non-restricted state, updating a corresponding one of said stored at least one restriction indication.

[0208] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: in response to receiving updated congestion information for a network slice used for a registered connection, comparing said received congestion load value with a corresponding congestion threshold value and where said compared values indicate a change to a restricted state, selecting a non-restricted network slice to establish a new connection and releasing a current packet data unit session for said network slice.

[0209] In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which at least one of said network slices are restricted; and the instructions, when executed by the at least one processor, further cause said apparatus to perform updating at least one timer associated with said at least one network slice with a respective one of said at least one time period; and inhibiting selecting said at least one restricted network slice during said time period.

[0210] In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which said congestion information is deemed to be valid, wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform

[0211] 32 updating a timer with said time period and on expiry of said timer to update stored congestion information to a default congestion load and threshold value.

[0212] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform determining from said congestion information at least one preferred nonrestricted network slice associated with a RAT; generating a request, said request comprising Network Slice Selection Assistance Information identifying said at least one preferred non-restricted network slice; and transmitting said request to said network.

[0213] In some example embodiments, said message comprises one of the following: a registration accept message, configuration update or deregistration message

[0214] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform transmitting an indication of said selected network slice to said network in a registration complete message.

[0215] In some example embodiments wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform determining that more than a predetermined number of network slices associated with one of said non-restricted RATs are restricted, selecting a different non-restricted RAT or a PLMN and initiating a mobility registration update or deregistration to connect to said different non-restricted RAT or PLMN.

[0216] According to various, but not necessarily all example embodiments of the invention there is provided an apparatus, comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said

[0217] 33 user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

[0218] In some example embodiments, said congestion information comprises a congestion load value.

[0219] In some example embodiments, said congestion information further comprises a congestion threshold value for said user equipment.

[0220] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining whether at least one of said multiple RATs is restricted for said user equipment; and generating said message to further include a restriction indication for said at least one restricted RAT and said congestion information to include congestion information concerning at least one nonrestricted RATs.

[0221] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining at least one time period during which said restriction indication is valid; and including an indication of said at least one time period in said message.

[0222] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining at least one time period during which said congestion information is deemed to be valid; and including said time period in said message.

[0223] In some example embodiments, said message comprises a registration accept message, configuration update or deregistration message.

[0224] In some example embodiments, the instructions, when executed by the at least one processor, further cause said apparatus to perform: generating a configuration update message indication comprising updated congestion information for said user equipment; and

[0225] 34 transmitting said configuration update message to said user equipment.

[0226] In some example embodiments, said apparatus is further caused to receive a request, said request comprising at least one Network Slice Selection Assistance Information identifying at least one preferred non-restricted network slice associated with a RAT for at least one PLMN for a user equipment, said apparatus being further caused to: determine whether said at least one preferred network slice is restricted or not; select at least one of said at least one preferred network slices in dependence upon a determination that said at least one of said at least one preferred network slices is not restricted and has a low congestion load; and including an indication of said at least one selected network slice within said message.

[0227] In some example embodiments, said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load value being greater than said congestion threshold value for said user equipment being indicative of said network slice being restricted.

[0228] According to various, but not necessarily all, example embodiments of the invention there is provided an apparatus, comprising: means for receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and means for using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0229] According to various, but not necessarily all example embodiments of the invention there is provided the apparatus, comprising: means for determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; means for generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least

[0230] 35 one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and means for transmitting said message to said user equipment.

[0231] The means may perform the optional features set out in relation to the apparatus mentioned above.

[0232] According to various, but not necessarily all, example embodiments of the invention there is provided an apparatus, comprising: circuitry configured for receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and circuitry configured for using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0233] According to various, but not necessarily all example embodiments of the invention there is provided the apparatus, comprising: circuitry configured for determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; circuitry configured for generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and circuitry configured for transmitting said message to said user equipment.

[0234] The circuitry may be configured perform the optional features set out in relation to the apparatus mentioned above. According to various, but not necessarily all example embodiments of the invention there is provided a method performed at an apparatus, said method comprising: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice associated with a RAT to use to request access to said PLMN.

[0235] In some example embodiments, said message further comprises at least one restriction indication and congestion information for at least one non-restricted RAT, the method further comprising: selecting one of: said non-restricted RAT or non-restricted network slice associated with a RAT to use to request access to said PLMN in dependence upon said congestion information for said non-restricted network slice associated with a RAT or said non-restricted RAT.

[0236] In some example embodiments, said congestion information comprises a congestion load value.

[0237] In some example embodiments, said congestion information further comprises a congestion threshold value.

[0238] In some example embodiments, said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load being greater than said congestion threshold value being indicative of a restriction for the network slice associated with the RAT.

[0239] In some example embodiments, said at least one restriction indication comprises an explicit restriction indication and said selecting comprises: comparing said congestion loads for the one or more of said network slices that are not explicitly indicated as being restricted with said corresponding congestion threshold values; determining a corresponding network slice to be restricted where said congestion load is greater than said threshold value; and selecting said non-restricted network slice. In some example embodiments, the method further comprises: storing at least some of said at least one restriction indication; and in response to receiving updated congestion information, comparing said received congestion load with a corresponding congestion threshold value and where said compared values indicate a change to a restricted or non-restricted state, updating a corresponding one of said stored at least one restriction indication.

[0240] In some example embodiments, the method further comprises: in response to receiving updated congestion information for a network slice used for a registered connection, comparing said received congestion load value with a corresponding congestion threshold value and where said compared values indicate a change to a restricted state, selecting a non-restricted network slice to establish a new connection and releasing a current packet data unit session for said network slice.

[0241] In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which at least one of said network slices are restricted; and the method further comprises: updating at least one timer associated with said at least one network slice with a respective one of said at least one time period; and inhibiting selecting said at least one restricted network slice during said time period.

[0242] In some example embodiments, said message further comprises at least one indication indicative of at least one time period during which said congestion information is deemed to be valid, wherein the method further comprises: updating a timer with said time period and on expiry of said timer to update stored congestion information to a default congestion load and threshold value.

[0243] In some example embodiments, the method further comprises: determining from said congestion information at least one preferred non-restricted network slice associated with a RAT; generating a request, said request comprising Network Slice Selection Assistance Information identifying said at least one preferred non-restricted network slice; and transmitting said request to said network.

[0244] In some example embodiments, said message comprises one of the following: a registration accept message, configuration update or deregistration message

[0245] In some example embodiments, the method further comprises: transmitting an indication of said selected network slice to said network in a registration complete message.

[0246] 38 In some example embodiments, the method further comprises: determining that more than a predetermined number of network slices associated with one of said non-restricted RATs are restricted, selecting a different non-restricted RAT or a PLMN and initiating a mobility registration update or deregistration to connect to said different non-restricted RAT or PLMN.

[0247] According to various, but not necessarily all example embodiments of the invention there is provided a method comprising: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

[0248] In some example embodiments, said congestion information comprises a congestion load value.

[0249] In some example embodiments, said congestion information further comprises a congestion threshold value for said user equipment.

[0250] In some example embodiments, the method further comprises: determining whether at least one of said multiple RATs is restricted for said user equipment; and generating said message to further include a restriction indication for said at least one restricted RAT and said congestion information to include congestion information concerning at least one non-restricted RATs.

[0251] In some example embodiments, the method further comprises: determining at least one time period during which said restriction indication is valid; and including an indication of said at least one time period in said message.

[0252] In some example embodiments, the method further comprises: determining at least one time period during which said congestion information is deemed to be valid; and including said time period in said message. In some example embodiments, said message comprises a registration accept message, configuration update or deregistration message.

[0253] In some example embodiments, the method further comprises: generating a configuration update message indication comprising updated congestion information for said user equipment; and transmitting said configuration update message to said user equipment.

[0254] In some example embodiments, the method further comprises: receiving a request, said request comprising at least one Network Slice Selection Assistance Information identifying at least one preferred non-restricted network slice associated with a RAT for at least one PLMN for a user equipment, the method further comprising: determining whether said at least one preferred network slice is restricted or not; selecting at least one of said at least one preferred network slices in dependence upon a determination that said at least one of said at least one preferred network slices is not restricted and has a low congestion load; and including an indication of said at least one selected network slice within said message.

[0255] In some example embodiments, said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load value being greater than said congestion threshold value for said user equipment being indicative of said network slice being restricted.

[0256] According to various, but not necessarily all, example embodiments of the invention there is provided a computer program comprising instructions which, when executed by the apparatus, cause the apparatus to perform: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0257] According to various, but not necessarily all example embodiments of the invention there is provided a computer program comprising instructions which, when executed by the apparatus, cause the apparatus to perform: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

[0258] According to various, but not necessarily all, example embodiments of the invention there is provided a computer program for performing the following: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0259] According to various, but not necessarily all example embodiments of the invention there is provided a computer program for performing the following: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

[0260] According to various, but not necessarily all, example embodiments of the invention there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0261] According to various, but not necessarily all example embodiments of the invention there is provided a non- transitory computer readable medium comprising program instructions stored thereon for performing at least the following: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

[0262] The instructions of the computer programs above may be for performing the optional features set out in relation to the method mentioned above.

[0263] A person of skill in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods. The tern non-transitory as used herein, is a limitation of the medium itself (i.e. , tangible, not a signal) as opposed to a limitation on data storage persistency (e.g. RAM vs ROM).

[0264] As used in this application, the term "circuitry” may refer to one or more or all of the following:

[0265] (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry) and

[0266] (b) combinations of hardware circuits and software, such as (as applicable):

[0267] (I) a combination of analog and / or digital hardware circuit(s) with software / firmware and

[0268] (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause The apparatus, such as a mobile phone or server, to perform various functions) and

[0269] (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.

[0270] 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.

[0271] As used herein, "at least one of the following: ” and "at least one of ” and similar wording, where the list of two or more elements are joined by "and” or "or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0272] The ordering of method steps set out above may not be critical or fixed and the exact ordering of the steps may be varied as appropriate. Although example embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. Features described in the preceding description may be used in combinations other than the combinations explicitly described.

[0273] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0274] Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

[0275] Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed thereon.

[0276] WE CLAIM:

[0277] 1. An apparatus, comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice of the PLMN associated with a RAT to use to request access to said PLMN.

[0278] 2. An apparatus according to claim 1, wherein said message further comprises at least one restriction indication and congestion information for at least one non-restricted RAT, the instructions, when executed by the at least one processor, further causing said apparatus to perform: selecting one of: said non-restricted RAT or non-restricted network slice associated with a RAT to use to request access to said PLMN in dependence upon said congestion information for said nonrestricted network slice associated with a RAT or said non-restricted RAT.

[0279] 3. An apparatus according to claim 1 or 2, wherein said congestion information comprises congestion load value.

[0280] 4. An apparatus according to claim 3, wherein said congestion information further comprises a congestion threshold value.

[0281] 5. An apparatus according to any preceding claim, wherein said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load being greater than said congestion threshold value being indicative of a restriction for the network slice associated with the RAT.

[0282] 45

Claims

6. An apparatus according to claim 4, wherein said at least one restriction indication comprises an explicit restriction indication and said selecting comprises: comparing said congestion loads for the one or more of said network slices that are not explicitly indicated as being restricted with said corresponding congestion threshold values; determining a corresponding network slice to be restricted where said congestion load is greater than said threshold value; and selecting said non-restricted network slice.

7. An apparatus according to any preceding claim wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: storing at least some of said at least one restriction indication; and in response to receiving updated congestion information, comparing said received congestion load with a corresponding congestion threshold value and where said compared values indicate a change to a restricted or non-restricted state, updating a corresponding one of said stored at least one restriction indication.

8. An apparatus according to any preceding claim, wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: in response to receiving updated congestion information for a network slice used for a registered connection, comparing said received congestion load value with a corresponding congestion threshold value and where said compared values indicate a change to a restricted state, selecting a non-restricted network slice to establish a new connection and releasing a current packet data unit session for said network slice.

9. An apparatus according to any preceding claim, wherein said message further comprises at least one indication indicative of at least one time period during which at least one of said network slices are restricted; and the instructions, when executed by the at least one processor, further cause said apparatus to perform updating at least one timer associated with said at least one network slice with a respective one of said at least one time period; and inhibiting selecting said at least one restricted network slice during said time period.

10. An apparatus according to any preceding claim, wherein said message further comprises at least one indication indicative of at least one time period during which said congestion information is deemed to46be valid, wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform updating a timer with said time period and on expiry of said timer to update stored congestion information to a default congestion load and threshold value.

11. An apparatus according to any preceding claim, wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform determining from said congestion information at least one preferred non-restricted network slice associated with a RAT; generating a request, said request comprising Network Slice Selection Assistance Information identifying said at least one preferred non-restricted network slice; and transmitting said request to said network.

12. An apparatus according to any preceding claim, wherein said message comprises one of the following a: registration accept message, configuration update or deregistration message13. An apparatus according to any preceding claim, , wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform transmitting an indication of said selected network slice to said network in a registration complete message.

14. An apparatus according to any preceding claim, wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining that more than a predetermined number of network slices associated with one of said non-restricted RATs are restricted, selecting a different non-restricted RAT or a PLMN and initiating a mobility registration update or deregistration to connect to said different non-restricted RAT or PLMN.

15. An apparatus, comprising: at least one processor; and at least one memory storing instructions that when executed by the at least one processor cause the apparatus at least to perform: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment; generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction47indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

16. An apparatus according to claim 15, wherein said congestion information comprises a congestion load value.

17. An apparatus according to claim 15 or 16, wherein said congestion information further comprises a congestion threshold value for said user equipment.

18. An apparatus according to any one of claims 15 to 17 wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining whether at least one of said multiple RATs is restricted for said user equipment; and generating said message to further include a restriction indication for said at least one restricted RAT and said congestion information to include congestion information concerning at least one nonrestricted RATs.

19. An apparatus according to any one of claims 15 to 18, wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining at least one time period during which said restriction indication is valid; and including an indication of said at least one time period in said message.

20. An apparatus according to any one of claims 15 to 19 wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform: determining at least one time period during which said congestion information is deemed to be valid; and including said time period in said message.21 . An apparatus according to any one of claims 15 to 20, wherein said message comprises a registration accept message, configuration update or deregistration message.

22. An apparatus according to any one of claims 15 to 21 wherein the instructions, when executed by the at least one processor, further cause said apparatus to perform:48generating a configuration update message indication comprising updated congestion information for said user equipment; and transmitting said configuration update message to said user equipment.

23. An apparatus according to any one of claims 15 to 22, wherein said apparatus is further caused to receive a request, said request comprising at least one Network Slice Selection Assistance Information identifying at least one preferred non-restricted network slice associated with a RAT for at least one PLMN for a user equipment, said apparatus being further caused to: determine whether said at least one preferred network slice is restricted or not; select at least one of said at least one preferred network slices in dependence upon a determination that said at least one of said at least one preferred network slices is not restricted and has a low congestion load; and including an indication of said at least one selected network slice within said message.

24. An apparatus according to any one of claims 15 to 23, wherein said restriction indication comprises said congestion information, said congestion information comprising congestion load and congestion threshold values, said congestion load value being greater than said congestion threshold value for said user equipment being indicative of said network slice being restricted.

25. A method performed at an apparatus, said method comprising: receiving a message comprising an indication of multiple radio access technologies RATs that a public land mobile network PLMN provides for accessing the PLMN, wherein access to the PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that at least one network slice of said multiple network slices is restricted for said apparatus, said message further comprising congestion information, said congestion information including information concerning a network slice of said multiple network slices that is not restricted for said apparatus; and using said congestion information when selecting a network slice associated with a RAT to use to request access to said PLMN.

26. A method comprising: determining that at least one network slice associated with at least one radio access technology RAT for accessing a public land mobile network PLMN is to be restricted for at least one user equipment;generating a message comprising an indication of multiple RATs that are provided for accessing said public land mobile network PLMN, wherein access to said PLMN according to at least one of said multiple RATs is via multiple network slices, said message further comprising at least one restriction indication indicating that said at least one network slice of said multiple network slices is restricted for said user equipment, said message further comprising congestion information including information concerning at least one network slice of said multiple network slices that is not restricted for said user equipment; and transmitting said message to said user equipment.

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