Patent Description:
The problem addressed by the present invention is to automatically switch from a public network subscription to a private network subscription while the mobile terminal is still attached to the public network.

In all these cases, a particular MNC code (Mobile Network Code) is affected to the subscribers. The MNC code is comprised in the IMSI (International Mobile Subscription Identifier) of the secure element (IMSI = MCC/MNC/MSIN).

Private networks have limited geographic coverage and there is a need to leverage coverage of public networks when the terminal (typically a smartphone or a M2M device) goes out of coverage of the private network.

This is represented in <FIG> that shows a private network 10a comprised entirely in a public network <NUM>. The private network (as referenced now by 10b) can also be only partially covered by the public network <NUM>. But private networks always need to be used when available. It is a purpose of the invention to be able to switch automatically from a public to a private network, and vice versa, depending on the availability of the private network:.

The constraints are however the followings:.

So the problem is to find a solution permitting to switch automatically from one network to the other (more precisely from public to private).

3GPP has defined roaming mechanisms between networks that rely on the information exchanged between the serving networks (where the User Equipment (UE) or Mobile Equipment (ME) is roaming) and the home network which is able to authenticate the UE/ME. This mechanism is described in 3GPP TS <NUM> V15. <NUM> (<NUM>-<NUM>) and represented in <FIG> (Automatic network selection mode).

In this figure, at step <NUM>, the ME attempts to register to the registered PLMN (Public Land Mobile Network) by scanning the EF_LOCI file.

At step <NUM>, the ME attempts to register to the HPLMN (Home PLMN).

This HPLMN can be a PLMN defined in the EF_IMSI file if there is no EHPLMN (Equivalent HPLMN) file or if this file is empty. EHPLMN stands for Equivalent HPLMN (Home PLMN). It contains the list of PLMNs which can be regarded as a Home PLMN. The items are listed in order of decreasing priority, meaning that the first PLMN in the list has the highest priority and the last item has the lowest priority.

A PLMN is defined in the EHPLMN file in priority order if this EHPLMN file exists and is not empty. "Priority order" means that the ME will in priority choose the PLMN that is listed first in the EHPLMN file, this file being the preferred one.

At step <NUM>, and if step <NUM> is not successful, the ME attempts to register according to the User Preferred Network List. For this purpose, it scans the PLMNwAct list of the secure element in priority order. PLMNwACT stands for 'User Controlled PLMN with Access Technology'. This parameter contains the list of (PLMN, Access Technology) pairs. This information is determined by the user and defines the preferred PLMNs of the user in priority order.

These PLMNs are listed in decreasing order of priority, meaning the first PLMN has the highest priority. This parameter plays important roles to determine which PLMN should be selected first under various cell selection, reselection test.

At step <NUM>, and if step <NUM> is not successful, the ME attempts to register according to the operator preferred network selection. For that, it scans the OPLMNwAct list stored in the secure element in priority order. OPLMNwACT stands for Operator controlled PLMN selector with Access Technology. This parameter is set by Network Operator. This is where a network operator puts other networks with which it has a roaming agreement. This parameter contains a list of (PLMN, Access Technology) pairs. These PLMNs are listed in decreasing order of priority, meaning the first PLMN of the list has the highest priority, the second PLMN of the list has a lowest priority than the first PLMN and a higher priority than the third PLMN of the list and so on. Finally at step <NUM>, if step <NUM> is not successful, the ME attempts to register to a network based on the strongest received signal.

A device connected to a visited network (meaning not connected to a PLMN defined by IMSI or PLMN listed in EHPLM) shall make periodic attempts to look for a higher priority PLMN following the selection mode described here above (from step <NUM>). The interval between attempts is nx6 minutes where n is defined in the EF HPPLMN file.

However, in private networks deployment (e.g. ad hoc telecommunication networks or IOPS networks) there is no inter-connections and roaming agreements between the private network and another network.

The technical problem to be solved is therefore to provide a solution to:.

The present invention focuses on the case where the service provider offers the services with different subscriptions which have distinct subscription identifiers (different IMSI, different long term keys Ki).

The alternatives of the proposed solution are:.

The problem is that the location of the private network needs to be known in advance by the device (pre-configured in the device), however localization and availability of the private network information cannot always be known by the public network. So switching may occur although the private network is not available.

In most public safety cases, for instance, it is not possible to know in advance where the tactical communication bubble will be present, thus localization of the tactical bubble cannot be provided.

Document <CIT> describes a method at a user equipment including a mobile equipment and a smartcard, the method receiving from a remote server a plurality of subscriber identities and a roaming policy; storing the plurality of subscriber identities and roaming policy on the smartcard; selecting, based on the roaming policy, a subscriber identity; and attaching to a network based on the selected subscriber identity.

In this document, a USIM is selected to connect to a network e.g. when roaming. To do so, a roaming applet changes the identity used by the UE. When this has been performed, the roaming applet in the UICC sends a refresh IMSI message to the ME. The ME then detaches from the mobile network and re-attaches with the new IMSI.

The invention proposes a solution to these problems.

More precisely, the present invention proposes a method according to claim <NUM>. Other features of the present invention are described in claims <NUM> to <NUM>.

The invention will be better understood by reading the following description of a preferred embodiment of the invention in regard of the figures that represent:.

<FIG> have been described in regard of the state of the art.

<FIG> represents a flowchart of steps of an example of the method according to the invention for switching from a public to a private network subscription.

This configuration private/public is only done as an example, the invention being also applicable to only public networks as it will be understood hereinafter.

The assumptions are here the followings:
There are three networks to be considered:.

The third network is the one of a public MNO that owns the infrastructure (base stations, HLR, VLR, back-end system,. ) permitting to the user to roam with the first IMSI/Ki of his MVNO in the network of the third public MNO. There is a roaming agreement between the MVNO and the public MNO (like for example between NRJ Mobile™ and Orange™ in France). In particular, there is information exchanged between the HLR of the first network of the MVNO and the third network of the public MNO during the authentication process of the device to the third network. In contrast, there are no roaming agreements between the second network owner (private network) and the first network owner (MVNO) nor the second network and the third network (public MNO). In particular, there is no information exchanged during the authentication process of the device to the second network (private network) between the second network and neither first nor third networks. The MVNO (the first MNO) has no radio coverage at least overlapping the radio coverage of the private network (second MNO).

The secure element has thus a subscription from the first network and is roaming on the third network. The secure element stores the second network's PLMN code and the third network's PLMN code in the OPLMN roaming file (EF_OPLMN). The second network's PLMN code has a higher priority than the third network's PLMN code, i.e. the secure element will select the second PLMN in priority (compared to the third PLMN).

This means that the EF_OPLMN file contains:.

As represented in <FIG>, the third network has a coverage including at least a part of the coverage of the second network.

In a first step, the terminal has lost his connectivity with the second network (with its private MNO). The user of the terminal has left the zone 10a or 10b of <FIG> and entered in the coverage of zone <NUM>. The coverage of zone <NUM> is that of the third MNO (the public network). At this stage, the user is in roaming situation (connected on the radio of the third MNO with the credentials (IMSI/Ki) of his MVNO (first network).

If the user enters again in the zone 10a or 10b covered by the second network (his private network), the terminal will attempt to attach to the private network (second PLMN) because it has a higher priority in the OPLMN roaming file compared to the public network (third network), but this second network will reject (after maximum nx6 minutes, depending on the value n stored in the EF_HPPLMN file), the attachment request sent by the terminal. This is because the credentials used by the terminal are those of the first network (MVNO), unknown by the second network (private network).

At such an occurrence, the invention proposes to:.

The terminal is then connected again to his private network.

The detection that the second network has rejected the attachment request of the terminal can be the reception of a NETWORK_REJECTION event from the terminal.

Another way to detect such a rejection is the fact that the second PLMN code has been stored in the EF_FPLMN file. This is represented in <FIG>.

<FIG> represents the messages exchanged for the flowchart of <FIG>.

In a first step <NUM>, the USIM <NUM> is connected to his MVNO <NUM> in roaming through the visited public PLMN <NUM>.

In a further step <NUM>, the ME <NUM> enters the coverage of the private network <NUM>. The ME then tries to attach to this network <NUM> by using the current IMSI (the IMSI of the MVNO <NUM>). But the private network <NUM> does not recognize this MVNO IMSI and rejects (step <NUM>) the attachment request permanently. A rejection message is then sent to the ME <NUM> that updates (step <NUM>) the list of the FPLMN in the USIM <NUM> (EF_FPLMN file).

At step <NUM>, a dedicated feature (can be in the form of an applet) of the USIM <NUM>:.

The USIM then (step <NUM>) sends a Refresh command to the ME <NUM> in order to ask for a registration (step <NUM>) with the private network <NUM>, using the newly activated private network <NUM> subscription. After a challenge/response process <NUM>, the USIM is connected to the private network <NUM> (step <NUM>).

<FIG> is a flowchart showing how in the state of the art a switch is done between a private and a public network when a user of a terminal gets out of the coverage of his private network.

In this figure, at step <NUM>, the terminal cooperating with the secure element detects a loss of service from the private network. The secure element then (step <NUM>) checks if the currently used IMSI is the IMSI of the private network. If no, the process ends (step <NUM>). If yes, at step <NUM>, the secure element clears the EF_LOCI file, updates the EF_IMSI file with the public IMSI and switches the Ki to the Ki associated to the public IMSI and sends a Refresh command to the terminal. The terminal then (step <NUM>) tries to authenticate to the public network by using this public IMSI (and the associated Ki) and at step <NUM> the terminal is connected to the public PLMN.

At step <NUM>, the secure element <NUM> is connected with his private network <NUM>. When getting out of coverage of this private network, a loss of connectivity between the ME <NUM> and the private network <NUM> is detected (step <NUM>). The ME <NUM> then updates the EF_LOCI file for allowing only emergency calls (step <NUM>). At step <NUM>, the secure element <NUM> activates its MVNO subscription and an applet clears the EF_LOCI file. At step <NUM>, the secure element <NUM> sends a Refresh command to the ME <NUM>.

At step <NUM>, the ME <NUM> detects that it is under coverage of the VPLMN <NUM> and tries (step <NUM>) to register to the MVNO <NUM> through the public network <NUM> with the corresponding IMSI. After a challenge/response process (step <NUM>), the USIM <NUM> is connected to his MVNO <NUM> through the public network <NUM>.

The invention applies when the first network is the one of a MVNO but also more generally when the first network is the network of a MNO with which the third network has roaming agreements with (national or international), the important point being that when leaving the second network (private) radio coverage, the ME enters in roaming situation. This will allow the consultation of the EF_OPLMN file.

A service provider can own the MVNO. This service provider has a specific PLMN code to provide connectivity services to private network users leveraging connectivity coverage from public networks, while having roaming agreement with local public networks. Higher priority is always given to private networks.

When using a service provider (MVNO) subscription, the users are always roaming on partner's public networks. Thus, the user equipment (terminal) will always automatically select higher priority roaming partner networks when available i.e. gives higher priority to a private network in the OPLMN file in this invention.

Based on network response (error codes) to Registration requests, the terminal will switch to corresponding private network subscription or use the service provider (MVNO) subscription. The invention enables to switch automatically from one network to another but always by putting the highest priority on the private network.

It leverages roaming mechanism where the mobile equipment scan the availability of a network with higher priority (private network in this case).

Claim 1:
A method for connecting a terminal (<NUM>) cooperating with a secure element (<NUM>) to a second network (10a, 10b), said secure element (<NUM>) having a subscription from a first network (<NUM>), wherein whilst said secure element (<NUM>) is roaming on a third network (<NUM>), said secure element (<NUM>) storing the PLMN code of said second network (10a, 10b), called second PLMN code, and the PLMN code of said third network (<NUM>), called third PLMN code, said second PLMN code having a higher priority than said third PLMN code in the OPLMN roaming file, said second PLMN having no roaming agreement with said first network (<NUM>) nor said third network (<NUM>), and said third network (<NUM>) having a coverage that overlaps at least a part of the coverage of said second network (10a, 10b), said method comprising, when it is detected that said second network (10a, 10b) has rejected the attachment request of said terminal (<NUM>):
a - Storing by a dedicated feature of said secure element (<NUM>) in the EF_IMSI file an IMSI, called second IMSI, from said second network (10a, 10b) and allocating the associated key Ki to this second IMSI;
b - Sending from said secure element (<NUM>) to said terminal (<NUM>) a Refresh command;
c - Performing by said terminal (<NUM>) an authentication procedure with said second IMSI and said associated key Ki in order to connect said terminal (<NUM>) to said second network (10a, 10b).