WO2007118846A1

WO2007118846A1 - System and method for controlling registration on a mobile telecommunications network

Info

Publication number: WO2007118846A1
Application number: PCT/EP2007/053596
Authority: WO
Inventors: Stuart Alexander Coles; Elizabeth Gwen Edwards; Robert Draper
Original assignee: Orange Sa
Priority date: 2006-04-13
Filing date: 2007-04-12
Publication date: 2007-10-25
Also published as: GB0607536D0; GB2437129A; EP2005779A1

Abstract

Subscriber equipment for use in a mobile telecommunications network, said subscriber equipment comprising: storage means for storing forbidden network identity data identifying at least one identity of a forbidden network and allowed network identity data identifying at least one identity of an allowed network; a processor for: comparing data indicative of an identifier of a network with said allowed network identity data; updating said forbidden network identity data with said identifier of a network in response to said comparing indicating that said network is not identified as an allowed network, thereby providing a way of inhibiting registration onto an undesirable network. Thus, subscriber equipment associated with a user A in a first country 1 may be inhibited from roaming onto a network 2 in a second country 2.

Description

System and Method for Controlling Registration on a Mobile Telecommunications Network

Field of the Invention The present invention relates to the control of roaming between mobile telecommunications networks.

Background of the Invention

Typically, a user of a mobile terminal subscribes with a mobile telecommunications network in a particular country. This is referred to as a "home" network. If coverage of the home network is lost, such as when the mobile terminal is taken abroad it is usually possible for the mobile terminal to request registration to a network which is not the home network. This process is known as "roaming". However, a situation sometimes occurs in which the mobile terminal is in a geographical location where the user of the mobile terminal would expect to be covered by a network provided in that country (such as the home network), but the signal strength of that network is not enough to provide network services. This may occur, for example near the boundaries of countries, where the signal strength of a network provided for a neighbouring country is stronger than that of the network provided for the country in which the mobile terminal is located. This can cause a call or other service initiated by the user of the mobile terminal to be routed via a network provided for a different country.

Accordingly, the call charge of such a call may be significantly higher than the user was expecting, especially in the case where the user would have expected the call or other service to be handled by the home network. Furthermore, more network signalling must take place, since the foreign network must communicate with the home network in order to register the mobile terminal, and to provide the mobile terminal with services, and to relay billing information between the different networks. Delays in the provision of the service may also occur, since more than one network is involved in initiating the service.

Further, in the case of incoming calls or other services which are intended to be received by the user of the mobile terminal would be routed via a network which is not the home network. Again, this may result in extra charges being incurred by the user and/or the party calling or initiating the service. Further, the user may not receive services such as messenger services, until the mobile terminal is re-registered onto the home network. This may cause delays in receiving such services or may cause the user not to receive the message at all. Furthermore, network services such as: caller identification; voicemail; e- mail; mobile internet services; applications such as WAP; push-to-talk services; call forwarding or divert, which the user expects to have access to may not be supported by the network on which the mobile terminal is registered.

WO 02/104051 discusses the above issues in relation to accidental roaming from the home network, and further discusses that the user of the mobile terminal may be oblivious to the fact that either an incoming or outgoing call is being routed via a network which is not the home network, even when the mobile terminal is present in the country corresponding to the home network. This document addresses the problem of the user being unaware of the routing of the call, and proposes a solution of warning the user by providing a different dialling tone or ring tone, or providing some other audible alert, such as a bleep.

Further, when a mobile terminal is roaming (i.e. the user of the mobile telephone is abroad, for example) it may be preferable to the user and/or the provider of the home network of the mobile terminal to have some control over the selection of the foreign network onto which the mobile terminal is registered. Again, this may be particularly useful if the mobile terminal is roaming near a country boundary, where the network coverage of a network provided by a neighbouring country is stronger, or in a region where a mobile terminal could register with a number of different networks. US 2004/0192306 discusses these issues, and discusses the provision of a remote preference unit, which resides in the home network. The home network controls the registration of the mobile terminal onto a foreign network by preventing the registration process if that network is not a preferred network. This document also discloses transmitting a list of preferred networks to the SIM of the user terminal. These are used to select a network for the mobile terminal to register on, in preference.

It is an object of embodiments of the present invention to prevent services for a mobile terminal being routed via a network other than an intended network.

Summary of the Invention

In accordance with a first aspect of the present invention there is provided subscriber equipment for use in a mobile telecommunications network, said subscriber equipment comprising: storage means for storing forbidden network identity data identifying at least one identity of a forbidden network and allowed network identity data identifying at least one identity of an allowed network; and a processor for: comparing data indicative of an identifier of a network with said allowed network identity data; and updating said forbidden network identity data with said identifier of a network in response to said comparing indicating that said network is not identified as an allowed network.

Thus, the subscriber equipment effectively "locks out" networks not according with the allowed network identity data, using a dynamic updating mechanism for the forbidden network identity data. This means that the subscriber equipment may be prevented from making any further attempt to connect to the network, and further, that any in-progress connection may be terminated.

The allowed network identity data may comprise data representative of a home network of said subscriber equipment. The allowed network identity data may comprise data derived from an international mobile subscriber identity number.

This means that registration to a network which is not the home network can be rejected, based on data indicative of the home network, which may be stored on the SIM.

The subscriber equipment may comprise a user interface for: providing at least one user-selectable option, said at least one user- selectable option being indicative of a request to inhibit network registration; and receiving data indicative of user selection of one of said at least one user- selectable option, wherein said processor is adapted for updating said forbidden network identity data with said identifier of a network in response to said comparing indicating that said network is not identified as an allowed network, and on the basis of said data indicative of user selection.

Accordingly, the invention provides subscriber equipment for selectively inhibiting network registration on the basis of a user input.

The user interface may provide said at least one user-selectable option on the basis of the processor comparing said data indicative of an identifier to said network identity data.

This means that the user need only be alerted to the fact that the mobile terminal has detected that it cannot connect to a network according to the network identity data. This means that the user can choose whether or not to allow the mobile terminal to register with an alternative network as and when this decision needs to be taken.

The processor may be further arranged for switching said subscriber equipment between first and second modes, in response to receiving data indicative of user selection, wherein: in said first mode said subscriber equipment is permitted to initiate network registration on a mobile telecommunications network in response to said subscriber equipment processing data indicative of an identifier of said network; and in said second mode said subscriber equipment is inhibited from initiating network registration on a mobile telecommunications network in response to said subscriber equipment processing data indicative of an identifier of said network.

The allowed network identity data may comprise data representative of a list of preferred networks.

This means that registration to a network which is not a preferred network can be rejected, based on data indicative of the preferred network.

The processor may be further arranged for disabling an application used for roaming on said subscriber equipment.

This means that no processing power is wasted: if the user has chosen to effectively inhibit the mobile terminal from roaming, or from registering with a non-preferred network any application which facilitates roaming will not be needed.

The processor may be further arranged for outputting a signal for refreshing a cache on said subscriber equipment comprising data representing forbidden networks. This means that any cache of files on the mobile terminal containing a forbidden list is also updated when the forbidden list itself is updated.

The processor may be further arranged for outputting a signal for triggering a request to activate a setting in a network, remote from the subscriber equipment. This means that the roaming functionality of the mobile terminal can be turned off at the network, but that this is initiated by user selection on the mobile terminal.

The processor may be at least partly disposed on a subscriber identity module. This has the advantage that the processor can be transferred between different mobile terminals, and can easily be updated by the provider of a telecommunications network

In accordance with a second aspect of the present invention, there is provided a mobile terminal for use in a mobile telecommunications network, said mobile terminal having a user interface for providing a user-selectable option, said user-selectable option being adapted for switching between: a first mode in which said mobile terminal is permitted to initiate network registration on a mobile telecommunications network in response to said mobile terminal processing data indicative of an identifier of said network; and a second mode in which said mobile terminal is inhibited from initiating network registration on a mobile telecommunications network in response to said mobile terminal processing data indicative of an identifier of said network, wherein said mobile terminal comprises storage means, and wherein in said second mode said mobile terminal is adapted for updating forbidden network identity data stored in said storage means with said identifier of said network.

Thus, the second aspect of the present invention allows a user of a mobile terminal to switch the mobile terminal between two modes, so that the user can choose to control the network registration activity of the mobile terminal, by selecting the second mode of the user-selectable options.

The storage means may be adapted for storing allowed network identity data and wherein said processor may be arranged for comparing said data indicative of an identifier to said allowed network identity data and for outputting a signal to inhibit the mobile terminal from initiating network registration if said identifier of said network does not correspond to said network identity data.

This allows the network registration activity to be controlled on the basis of network identity data. Further features and advantages of the invention will become apparent from the following description of preferred embodiments of the invention, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings Figure 1 is a block diagram of a known mobile communications network;

Figure 2 is a block diagram of a mobile terminal according to an embodiment of the present invention;

Figure 3 is a schematic diagram showing a network overlapping a country border;

Figure 4 is a schematic diagram showing a call between two users in the same country, in which the call is routed via a foreign network;

Figure 5 is a diagram showing the user selectability of the roaming functionality according to embodiments of the present invention; Figure 6 is a flow diagram showing the operation of a first arrangement of a first embodiment of the present invention;

Figure 7 is a flow diagram showing the operation of the mobile terminal when it boots up;

Figure 8 is a flow diagram showing the operation of a second arrangement of a first embodiment of the present invention;

Figure 9 is a flow diagram showing the operation of a second embodiment of the present invention.

Detailed Description of the Invention Figure 1 shows a GSM network, referred to as a public land mobile network (PLMN), having a location area identifier (LAI) made up of a mobile country code (MCC) having 3 decimal digits; a mobile network code (MNC) having 2 decimal places; and a location area code (LAC) having a maximum of 5 decimal places. This is in itself known and will not be described in detail. A mobile switching centre (MSC) 2 is connected via communication links to a number of base station controllers (BSCs) 4. The BSCs 4 are dispersed geographically across areas served by the mobile switching centre 2. Each BSC 4 controls one or more base transceiver stations (BTSs) 6 located remote from, and connected by further communication links to, the BSC. Each BTS 6 transmits radio signals to, and receives radio signals from, mobile terminals 8 which are in an area served by that BTS. That area is referred to as a "cell". A GSM network is provided with a large number of such cells, which are ideally contiguous to provide continuous coverage over the whole network territory.

A mobile switching centre 2 is also connected via communications links to other mobile switching centres in the remainder of the mobile communications network 10, and to a public service telephone network (PSTN), which is not illustrated. The mobile switching centre 2 is provided with a home location register (HLR) 12 which is a database storing subscriber authentication data including the international mobile subscriber identity (IMSI) which is unique to each mobile terminal 8. The IMSI is also stored in the mobile terminal in a subscriber identity module (SIM) along with other subscriber- specific information.

Figure 2 shows a mobile terminal 8 comprising a transmit/receive aerial 16, a radio frequency transceiver 18, a speech coder/decoder 20 connected to a loudspeaker 22 and a microphone 24, a processor circuit 26 and its associated memory 28, an LCD display 30 and a manual input port (keypad) 32. The mobile terminal is connected to a removable SIM 34 via electrical contacts 35 to provide a data- transfer interface between the SIM and the mobile terminal. The SIM comprises a storage area 36, and a processor 38, for running a SIM-based applet, for example. In a known conventional GSM (Global System for Mobile communications) system, each mobile terminal, such as a mobile telephone handset, is provided with such a SIM, which is inserted into the mobile terminal in order to allow the mobile terminal to receive services in a GSM network from a particular service provider or network operator.

In a GSM or UMTS network a unique number is assigned to each mobile phone user. This number is known as an international mobile subscriber identity (IMSI). The number is stored on the SIM, and is sent to the network and used to look up other details of the mobile terminal in the HLR.

An IMSI is usually fifteen digits long. However, they can be shorter (e.g. MTN South Africa's are 14 digits). The first three digits are the MCC, and the next digits are the MNC. The MNC can be either two digits long (conventional e.g. in Europe) or three digits long (conventional in North America); the remaining digits, up to the maximum length are the unique subscriber number (MSIN) within the network's customer base.

The home network identity (HNI) is the combination of the MCC and the MNC. The HNI is the number which fully identifies a subscriber's home network.

As mentioned briefly above, GSM systems allow for a subscriber to use their mobile terminal when travelling outside the geographical coverage area of the home network; this is referred to as "roaming". In this way the subscriber may automatically make or receive voice calls, send and receive data, or may access other services by using a visited network. The network operators establish roaming based on roaming agreement, defining mobility management, authentication procedures, billing arrangements and other terms.

When a mobile terminal loses network coverage of its home network (as defined by the HNI) roaming is conducted by a location registration procedure. The mobile terminal sends a request for registration to a current network to the BSS of the foreign network. The request contains the IMSI of the SIM in the mobile terminal, and is forwarded to a visitor location register (VLR). The VLR communicates with the HLR to authorise the registration. The VLR generates a random temporary mobile subscriber identity (TMSI). The TMSI is then forwarded to the mobile terminal and stored by the mobile terminal in nonvolatile storage (either on the mobile terminal itself, or the SIM, or a combination of both). If authentication has been successful the subscriber is assigned a mobile terminal roaming number (MSRN), which is stored in the HLR together with the LAI. In a GSM or UMTS network the SIM card stores information related to a particular subscription with a service provider. For third generation (3G) devices, the corresponding module is the universal integrated circuit card

(UICC). In the DECT standards, the corresponding module is known as a DECT authentication module (DAM).

The term subscriber identification module or SIM will be used throughout the specification to include any such module for use in a mobile telecommunications environment.

Figure 3 is a schematic diagram showing a situation in which a user A and a user B are in country 1. The home network of both users in country 1 is network 1. However, user A is located near to the boundary with country 2, which provides a network 2. The coverage of networks 1 and 2 is represented schematically by respective ellipses. In Figure 3 user A is located in a position in which there is no coverage from network 1, but in which there is coverage from network 2. In this case the mobile terminal of user A has conducted

"accidental cross-border roaming", and is registered onto network 2.

Figure 4 is a schematic diagram showing a situation where user A, in the position shown in Figure 3, places a call to user B. Even though user A and user B are located in the same country (country 1), and have the same home network (network 1) user A is not currently registered on network 1. This means that the call from user A to user B is first routed via network 2 and secondly via network 1.

In the case where the user A did not realise that their mobile terminal was "roaming" an unexpectedly high call charge may be generated, since the user would expect the call to be billed at his normal rate. Further, in the case where user B calls user A, user A may still incur higher call charges, if the provider of the mobile telecommunications network levies charges on incoming calls whilst roaming. First embodiment

A first embodiment of the present invention will now be described with reference to Figure 5. Figure 5 shows a flow diagram showing stages of a user- selectable interface according to a first arrangement of the first embodiment of the present invention, in which the user can choose to prevent the mobile terminal from roaming. In step 1 the user is presented with two options "Don't Roam" or "Enable Roaming", and may highlight one of these two options by scrolling, and may select one of the options using a soft key. The user can open the screen which allows them to select between the options of "Don't Roam" or "Enable Roaming" from the options presented by the user interface of the mobile terminal. This causes a SIM-based applet to run and to perform the steps of the flow diagram of Figures 5 and 6. The case where the user selects "Don't Roam" is shown in step S2, where a message reminding the user that they will not be able to make or receive calls if the mobile terminal cannot detect the home network. The user can accept this by pressing a soft key. A confirmation screen indicating that roaming has been turned off is shown in step S3.

The applet then performs the steps of Figure 6. In step S4 the mobile terminal performs a network search. Step S5 represents the case where no network is found. In this case the mobile terminal conducts a periodic network search. On the other hand, in step S7 a network is found by the mobile terminal. In step S8 the SIM compares a network identifier of the found network with the IMSI of the SIM, to determine whether the found network is the home network (i.e. to determine whether the found network corresponds to allowed network identity data). If the found network is the home network as in step S9 the applet does not conduct further processing until coverage of the home network is lost in step 10. Then the mobile terminal searches for a network again.

In the case when the found network is not the home network, as in step SI l, the details (such as a network identifier) of the found network are put into a SIM-based list of forbidden networks (FPLMN) in step S12. The FPLMN list is usually restricted in length. If the list is full any entry to the list will replace the oldest entry in the list. When the network identifier is put into the FPLMN list the SIM will notify the mobile terminal that the forbidden list has been updated. This will cause the mobile terminal to terminate the connection with that network (for example, by transmitting no further signals or data to that network), if the mobile terminal has already registered onto the network, and the mobile terminal will not attempt subsequently to register onto that network. The mobile terminal will then perform a further search for a network, and select a new network. Alternatively, if the mobile terminal has not registered with the network it will not attempt to do so. In order to terminate the registration with the network or prevent registration on the network the applet may send a signal to the mobile terminal requesting that it refresh its cache of forbidden networks taken from the SIM. The mobile terminal then searches for a further network in step S4, disregarding any networks in the forbidden list, and the process described above is repeated.

Figure 7 is a flow diagram showing the operation of the mobile terminal when the phone turns on or boots up in step S20. In the case shown in step S21, in which the applet was used before, and was set into the "Don't Roam" state the method steps of Figure 6 are performed. However, if the applet was previously used and was set into the "Roaming Enabled" state in step S22 the normal roaming function is conducted in step S24. Similarly, if the applet was not used before, the normal roaming function is also carried out in step S24.

The normal roaming functionality involves reading the LOCI stored on the SIM, and trying to find the last network that the mobile terminal was connected to in step S25. In step S26 if the mobile terminal does not find the last used network it tries to find the home network in step S27. Alternatively, in step S28, the mobile terminal finds the last used network (either the home network in step S29 or a foreign network in step S30).

The normal roaming functionality may, for example, be that disclosed in WO 2004/049744, in which a further SIM based applet performs an improved management of a list of preferred networks for roaming. In the case where any other applets relating to roaming are present on the SIM, the applet according to embodiments of the present invention preferably disables this other applet if the user selects the "Don't Roam" option.

A second arrangement of the first embodiment of the present invention will now be described in relation to Figure 8. The second arrangement of the first embodiment differs from the first arrangement in that the user chooses whether to allow the mobile terminal to roam at the point when the mobile terminal would actually roam, if there was no restriction on this. In order to achieve this the user can be presented with a third option of "Ask before roaming" in the screen of the user interface shown in step S 1 of Figure 5. Alternatively, the SIM can be provided with a default setting, set by the network provider, for example, to ask the user before roaming.

A number of the steps are common to Figure 8 and Figure 6, and a discussion of these has been omitted. In Figure 8 after a found network has been identified as a foreign network in step SH ' the applet triggers a prompt to be displayed to the user to warn the user that the coverage of the home network has been lost. The prompt further asks the user to indicate, by use of a soft key, for example, whether to enable roaming or whether to tell the mobile terminal not to roam in step S40. If the user selects the option to enable roaming the normal roaming function is then conducted in step S41. If the user indicates in step S42 that he does not wish the mobile terminal to roam, the details of the found network are put into the FPLMN list, and the above discussion in relation to Figure 6 applies.

In this way the user does not need to remember to set the phone to enable or to prevent roaming, since they will be prompted as and when they need to be. In a third arrangement of the first embodiment of the present invention the user-selectable option of "Don't Roam" shown in step Sl of Figure 5 has the effect of sending a request to the network to disable the roaming functionality of the mobile terminal. The request may interfere with the request for roaming in the network, or may cause the network to send a signal to the mobile terminal to add a network identifier to the forbidden list on the SIM. Second embodiment

In a second embodiment of the present invention use is made of a list of preferred networks stored in the storage area 36 of the SIM. The list contains entries of such preferred PLMNs, wherein the PLMN is listed using a code. The code includes the mobile country code (MCC) followed by the mobile network code (MNC). The list of preferred PLMNs is ordered by priority, i.e. the entries on top of the list have a higher priority compared to the entries further down the list when a network is selected for providing roaming services.

The list of preferred PLMNs is usually pre-programmed by the network operator before sale of the SIM. The list may be updated by the network operator, for example if the operator changes the roaming agreement with other network providers. This may be done with help of a card reader at a service centre. Alternatively, this can be done remotely "Over the Air" (OTA) using the short message service (SMS) as described in European Patent EP0562820 or using the GSM infrastructure for remotely managing SIM files as described in the GSM specification 03.48.

The preferred networks are usually networks which cooperate with a particular network provider or which offer particular favourable roaming conditions for the network provider or subscriber. The subscriber may also have an interest in using network providers which cooperate with the home network provider if he is roaming abroad. In this way the user may be offered the same or similar services as from his home service provider.

If a subscriber switches on his mobile terminal when he is abroad, the file of preferred PLMNs is read and the terminal automatically selects a network for the country in which the subscriber is roaming.

In prior art systems if no preferred network is found for the particular country, the mobile terminal usually selects the network providing the strongest signals. Further, the FPLMN list can be filled by the home network provider with codes of network which must not be selected if the subscriber is roaming abroad. However, the second embodiment of the present invention uses these lists in a different way, as discussed below.

The second embodiment of the present invention will be described with reference to Figure 9. Figure 9 shares some of the steps of Figure 6, and a discussion of the common steps will be omitted. In the second embodiment when a network is found, an identifier relating to that network is compared to the preferred PLMN list (as shown in step S50 in Figure 9), rather than to the IMSI as in the first embodiment. Thus, the preferred PLMN list comprises allowed network identity data. If the network identifier corresponds to that of a network stored in the preferred list in step S51 that network is used until network coverage is lost in step S52. However, if the network identifier does not correspond to any of the networks for which details are stored in the preferred list, (shown in step S53) the details of the found network are put into the FPLMN list in step S54. In this case, the applet on the SIM sends a signal to the mobile terminal to refresh the mobile terminal's cache including the current FPLMN list. When the network identifier is put into the FPLMN list the mobile terminal will terminate the connection with that network, if the mobile terminal has already registered onto the network, and the mobile terminal will not attempt subsequently to register onto that network. Alternatively, if the mobile terminal has not registered with the network it will not attempt to do so. In order to break the registration with the network or prevent registration on the network the applet may send a signal to the mobile terminal requesting that it refresh its cache of forbidden networks taken from the SIM. The mobile terminal then breaks contact with the current network, and searches for a further network in step S4, disregarding any networks in the forbidden list and the process described above is repeated. In this way, the preferred list is used to determine the only networks that the mobile terminal can register with.

The second embodiment of the present invention can also be conducted by a SIM-based applet. This applet can also be initiated by and request user selection of the options of whether to restrict the networks used in roaming to those on the preferred list. Alternatively, the applet can be controlled by the network provider, so that the mobile terminal only registers with networks associated with the same network provider, for example. In the case where the roaming restriction is user selectable the option described in the second arrangement of the first embodiment can be applied, so that the user is prompted about whether to use a network that is not on the preferred list, as and when the location of the mobile terminal requires this. Further, the third arrangement of the first embodiment can also be applied in the case where the roaming restriction is user selectable, so that a network setting is initiated by the user in order to set or remove the roaming restriction. The first and second embodiments of the present invention can be applied to a SIM having two or more lines (i.e. two or more IMSIs) associated with it. In this case, any of the settings mentioned herein can be made globally for all of the lines on the SIM, so that all lines are set to "Don't Roam", for example. Alternatively, the settings can be made for each line individually, so that the user can set one line, such as a personal line, to "Don't Roam", and a second line, such as a business line, to "Enable Roaming".

The above embodiments are to be understood as illustrative examples of the invention. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. Subscriber equipment for use in a mobile telecommunications network, said subscriber equipment comprising: storage means for storing forbidden network identity data identifying at least one identity of a forbidden network and allowed network identity data identifying at least one identity of an allowed network; and a processor for: comparing data indicative of an identifier of a network with said allowed network identity data; and updating said forbidden network identity data with said identifier of a network in response to said comparing indicating that said network is not identified as an allowed network.

2. Subscriber equipment according to claim 1 , wherein said allowed network identity data comprises data representative of a home network of said subscriber equipment.

3. Subscriber equipment according to claim 2, wherein said allowed network identity data comprises data derived from an international mobile subscriber identity number.

4. Subscriber equipment according to any preceding claim, comprising a user interface for: providing at least one user-selectable option, said at least one user- selectable option being indicative of a request to inhibit network registration; and receiving data indicative of user selection of one of said at least one user- selectable option, wherein said processor is adapted for updating said forbidden network identity data with said identifier of a network in response to said comparing indicating that said network is not identified as an allowed network, and on the basis of said data indicative of user selection.

5. Subscriber equipment according to claim 4, wherein said user interface provides said at least one user-selectable option on the basis of the processor comparing said data indicative of an identifier to said network identity data.

6. Subscriber equipment according to claim 4 or 5, wherein said processor is further arranged for switching said subscriber equipment between first and second modes, in response to receiving data indicative of user selection, wherein: in said first mode said subscriber equipment is permitted to initiate network registration on a mobile telecommunications network in response to said subscriber equipment processing data indicative of an identifier of said network; and in said second mode said subscriber equipment is inhibited from initiating network registration on a mobile telecommunications network in response to said subscriber equipment processing data indicative of an identifier of said network.

7. Subscriber equipment according to any preceding claim, wherein said allowed network identity data comprises data representative of a list of preferred networks.

8. Subscriber equipment according to any preceding claim, wherein said processor is further arranged for disabling an application used for roaming on said subscriber equipment.

9. Subscriber equipment according to any preceding claim, wherein said processor is further arranged for outputting a signal for refreshing a cache on said subscriber equipment comprising data representing forbidden networks.

10. Subscriber equipment according to any preceding claim, wherein said processor is further arranged for outputting a signal for triggering a request to activate a setting in a network remote from the subscriber equipment.

11. Subscriber equipment according to any preceding claim, wherein said processor is at least partly disposed on a subscriber identity module.

12. A method of inhibiting network registration of subscriber equipment in a mobile telecommunications network comprising: providing forbidden network identity data identifying at least one identity of a forbidden network and allowed network identity data identifying at least one identity of an allowed network; receiving data indicative of an identifier of a network; said subscriber equipment comparing data indicative of said identifier of a network with allowed network identity data, updating said forbidden network identity data with said identifier of a network in response to said comparing indicating that said network is not identified as an allowed network.

13. A method according to claim 12, wherein said allowed network identity data comprises data representative of a home network of said subscriber equipment, and the method further comprises updating said forbidden network identity data with said identifier of a network in response to said comparing in the case where said network is not identified as the home network.

14. A method according to claim 13, wherein said allowed network identity data comprises an international mobile subscriber identity number.

15. A method of inhibiting network registration according to any of claims 12 to 14, further comprising: providing at least one user-selectable option on an interface of said subscriber equipment, said at least one user-selectable option being indicative of a request to inhibit network registration; receiving data indicative of user selection of one of said at least one user- selectable option on an interface; and updating said forbidden network identity data with said identifier of a network in response to said comparing indicating that said network is not identified as an allowed network, and on the basis of said data indicative of user selection.

16. A method according to claim 15, wherein said step of receiving data indicative of an identifier of a network occurs prior to said step of providing at least one user-selectable option, and said user-selectable option is provided on the basis of said comparing.

17. A method according to claim 15 or 16, further comprising: switching said subscriber equipment between first and second modes, in response to receiving said data indicative of user selection, wherein: in said first mode said subscriber equipment is permitted to initiate network registration on a mobile telecommunications network in response to said subscriber equipment processing data indicative of an identifier of said network; in said second mode said subscriber equipment is inhibited from initiating network registration on a mobile telecommunications network in response to said subscriber equipment processing data indicative of an identifier of said network.

18. A method according to claim 12, wherein said allowed network identity data comprises data representative of at least one preferred network, and the method further comprises updating said forbidden network identity data with said identifier of a network in response to said comparing in the case where said received data indicates a network which is not a preferred network.

19. A method according to any of claims 12 to 18, further including disabling an application used for roaming on said subscriber equipment.

20. A method according to any of claims 12 to 19, further including outputting a signal for refreshing a cache on said subscriber equipment comprising data representing forbidden networks.

21. A method according to any of claims 12 to 20, further comprising outputting a signal for triggering a request to activate a setting in a network, remote from the subscriber equipment.

22. An application for installation on a subscriber identity module, being adapted to perform the method of any of claims 12 to 21.

23. A signal encoding data including an application as claimed in claim 22.

24. A mobile terminal for use in a mobile telecommunications network, said mobile terminal having a user interface for providing a user- selectable option, and a processor for processing data indicative of an identifier of a network, said user-selectable option being adapted for switching between: a first mode in which said mobile terminal is permitted to initiate network registration on a mobile telecommunications network in response to said mobile terminal processing data indicative of an identifier of said network; and a second mode in which said mobile terminal is inhibited from initiating network registration on a mobile telecommunications network in response to said mobile terminal processing data indicative of an identifier of said network, wherein said mobile terminal comprises storage means, and wherein in said second mode said mobile terminal is adapted for updating forbidden network identity data stored in said storage means with said identifier of said network.

25. A mobile terminal according to claim 24, wherein said storage means is adapted for storing allowed network identity data and wherein said processor is arranged for comparing said data indicative of an identifier of said network to said allowed network identity data and for outputting a signal for inhibiting the mobile terminal from initiating network registration if said identifier of said network does not correspond to said network identity data.

26. A method of inhibiting network registration of a mobile terminal in a mobile telecommunications network, comprising providing a user-selectable option; switching said mobile terminal between a first mode in which said mobile terminal is permitted to initiate network registration on a mobile telecommunications network in response to said mobile terminal processing data indicative of an identifier of a network, and a second mode in which said mobile terminal is inhibited from initiating network registration on a mobile telecommunications network in response to said mobile terminal processing data indicative of an identifier of a network by updating forbidden network identity data with said identifier of said network, based on said user selectable option.

27. A method according to claim 26, further comprising comparing said data indicative of an identifier of a network to stored allowed network identity data; and outputting a signal to inhibit the mobile terminal from initiating network registration if said identifier of said network does not correspond to said network identity data.