WO2001086995A1

WO2001086995A1 - Method for re-selection of a mobile telephone nominal network

Info

Publication number: WO2001086995A1
Application number: PCT/FR2001/001286
Authority: WO
Inventors: Benoît PRADY; Denis Prouvost
Original assignee: France Telecom
Priority date: 2000-05-05
Filing date: 2001-04-26
Publication date: 2001-11-15
Also published as: FR2808645B1; AU2001256418A1; FR2808645A1

Abstract

The invention concerns a method for reselection of a first operator telecommunication network, called nominal network, among networks belonging to different operators, called visited networks, each network being capable of relaying communications of a mobile telephone equipped with a SIM card present in their coverage zone and each network having an identity (MNC, MCC), the mobile telephone copying the identity of the so-called current network with which it is registered at a given time. The method comprises steps which consist in: storage (1) by the SIM card of the identity (MNC0, MCC0) of the nominal network; comparison (2) by the SIM card of the identity (MNC, MCC) of the current network copied by the mobile telephone with the identity (MNC0, MCC0) of the nominal network and, when the compared identities are different, fixing (3) a specific locating information contained in a specific file at a specific value and, sending (4) a specific command to the mobile telephone indicating to it that the file has been modified.

Description

METHOD FOR RE-SELECTING THE NOMINAL NETWORK OF A TELEPHONE

MOBILE

Field of the invention

The present invention relates to a method for re-selecting a nominal network of a mobile telephone; the nominal network being the network belonging to the telecommunications operator to which the user of the mobile telephone is contractually bound.

The invention finds a very advantageous application in that it allows, after the switching of a GSM mobile telephone equipped with a SIM card on a visited network, that is to say a network other than its nominal network, to carry out as soon as possible and automatically the switchover of the telephone to its nominal network. A GSM mobile phone equipped with a so-called subscriber identity module, SIM card, abbreviation of the terms Subscriber Identity Module, is a mobile phone compatible with the GSM standard, abbreviation of the Anglo-Saxon terms Global System for Mobile communications. A visited network can be a network configured with GSM standard compatible transceiver relays or, a network configured with relays embedded in satellites provided that the user is equipped with a mobile phone that can operate in both configurations ; relays relaying radio communication between the network and the mobile phone. The visited network can in particular be a terrestrial network in accordance with the EDGE standard, abbreviation of the Anglo-Saxon terms Enhanced Data Rates for the GSM Evolution, or UMTS, abbreviation of the Anglo-Saxon terms Universal Mobile Telecommunications System. The switching of the mobile phone to a visited network depends on the location of the mobile phone and is caused by a movement of the mobile phone, in particular a movement of the mobile phone in a border area.

Description of the Prior Art

Currently, a GSM mobile phone equipped with a SIM card includes different files, one of which is designated by the reference EF _L OCI according to the GSM standard. This EF _LOCI file is stored in the SIM card and it contains location information:

- MNC, abbreviation of the Anglo-Saxon terms Mobile Network Code, which gives the network code of the telecommunications operator which relays the mobile phone communications at a given time, this network is called the current network and,

MCC, abbreviation of the Anglo-Saxon terms Mobile Country Code, which gives the code of the country of the telecommunications operator whose network relays the communications of the mobile phone at a given time, this country is said to be current country, MNC and MCC define l identity of the current network,

"Location update status" or, "Location update status" according to English terminology, which gives the status of the last attempt to update the location. This state can be: "updated location"("updated" according to English terminology), "not updated location"("notupdated" according to English terminology), "unauthorized network"(" PLMN not allowed ”according to Anglo-Saxon terminology) or“ area not allowed ”(“ Location Area not allowed ”according to Anglo-Saxon terminology). The status “network not authorized” indicates that the network identified by the MNC and MCC information contained in the EFL _OCI file is not authorized on the mobile phone.

The mobile phone makes a copy of the MNC and MCC location information present in the SIM card and stores it in a fast memory independent of the SIM card. This copy is constantly updated by the mobile phone, it contains information on the current location of the mobile phone. When the "Location update status" is set to "network not authorized", the mobile phone registers the network, identified by the MNC and MCC information contained in the EF _LOCI file, in the list of prohibited networks and he is trying to contact a network. As a priority, the mobile phone tries to contact its home network. According to the GSM standard, there are commands grouped into a set which has been given the name of SIM toolkit. In this set, there is a first command called "location request", or "Provide Local Information" according to English terminology, which allows the SIM card to retrieve location information copied by the mobile phone. This first command allows the SIM card to know in particular the identity of the current network, MNC and MCC. And, there is a second command called "refresh", or "Refresh" according to English terminology, which allows to notify the mobile phone that a modification of the files contained in the SIM card has been made.

The mobile phone uses the services of the operator to which the user of the mobile phone is contractually used as long as the mobile phone remains in the area covered by the transmitter / receiver relays of the operator's network; each relay covering a specific area called ceUule. In this context, the location information of the mobile telephone supplied by the “location request” command is equal to MNC ₀ and MCC ₀ which correspond to the location information allocated to said operator. When the user of the mobile telephone moves to the limit of coverage of a first relay and when it is not in communication with a correspondent, the switching of the mobile telephone to a second relay takes place there. If the second relay belongs to a network of another operator, the changeover takes place on condition that the operators have established between themselves a so-called roaming agreement, or roaming according to English terminology. At the end of the changeover, on the one hand the mobile phone is entered in the list of mobile phones managed by the network of the new operator and, on the other hand the location information of the mobile phone provided by the command "request for location Are equal to MNd and MCCi which correspond to the coordinates of the new operator. Conversely, when the user moves to the limit of coverage of the network of the second operator and enters the area covered by the network of the first operator, the mobile phone switches to a relay of the network of the first operator provided that the user is not previously in communication with a correspondent.

However, when the area covered by the network of the second operator overlaps with the area covered by the network of the first operator, the mobile phone remains registered in the list of mobile phones managed by the same network as long as it remains in the covered area. through said network. Thus, if the coverage area of the network of the first operator has a hole in the overlap area, there is tilting of the mobile phone on the network of the second operator as soon as the mobile phone enters this hole. On the other hand, when the mobile telephone leaves the hole while remaining in the overlapping zone, it remains registered in the list of mobile telephones managed by the network of the second operator. Consequently, the first operator suffers a loss because he does not manage the mobile phone of the user with whom he is contracted, although his network covers the overlapping area in which the user of the mobile phone is located. .

In the case of a mobile telephone compatible with GSM networks and satellite-based networks, the scenario is similar and can occur over the entire area of overlap of the coverage areas of said networks; this overlap zone corresponding to the entire coverage area of the nominal network since the network based on sateUites is present theoretically everywhere. So in the presence of a nominal network coverage hole, there is switching of the mobile phone to the satellite-based network. On the other hand, when the mobile telephone leaves the hole of coverage of the nominal network while remaining in the zone of overlap of the two networks, it remains registered in the list of mobile telephones managed by the network based on satellites.

The GSM standard only provides for automatic re-selection of the nominal network in the event of loss of the current network. During an automatic re-selection, the GSM standard plans to attempt to re-select the nominal network as a priority, then, if this attempt fails, it provides for the selection of one of the other available networks. Following an attempt to select a network, the mobile phone updates the EF _L ocι file by entering the MCC, MNC data of the possible network selected, as well as the new status of the "Update status". of location ”. This last parameter can in particular contain "network not authorized" if the last network which was the subject of the selection attempt is not authorized. In the event that there has been an attempt to select an unauthorized network, the terminal updates the list of prohibited networks by inserting the network which was the subject of the selection attempt.

Also, the technical problem to be solved by the object of the present invention is to propose a method for re-selecting a telecommunication network of a first operator, said nominal network, among networks belonging to different operators than They are terrestrial or satellite-based, known as visited networks, each network being able to relay communications from a mobile phone equipped with a SIM card present in their coverage area and each network having an identity MNC, MCC, the mobile phone copying the identity of the so-called current network with which it is registered at a given instant, which allows the mobile phone to be automatically switched back to the nominal network after switching to a visited network, the switchover having to take place when the mobile phone enters the area covered by the nominal network.

Summary of the invention

A solution to the technical problem posed consists, according to the present invention, in that said re-selection method comprises the steps which consist in: memorizing by the SIM card the identity MNCo, MCCo of the nominal network, - to be compared by the card SIM the identity MNC, MCC of the current network copied by the mobile phone to the identity MNC ₀ , MCC ₀ of the nominal network and, when the identities compared are different, to fix a determined location information contained in a determined file EF _L ocι at a determined value, to send a determined command to the mobile telephone signaling that the EFLO _CI file has been modified. Thus, the invention, which relates to a method for re-selecting the nominal network of a mobile telephone after the mobile telephone has switched over to a network of a second operator, modifies determined location information contained in the EF _LOCI file - This modification consists in fixing a determined location information, “Status of the location update”, at a determined value, “network not authorized”. After the modification of the file, the SIM card sends a specific command, "refresh" in the case of the GSM standard, which warns the mobile phone that the file has been modified and that, therefore, it must read it again. The current network being unauthorized, the mobile phone tries to re-select its nominal network. Thus, if the mobile terminal is covering its nominal network, the nominal network is re-selected.

In a particular mode of implementation, the method also consists in modifying, by the SIM card, other location information, MNC and MCC, contained in the file EF _LOCI , by reinitializing this location information. This reinitialization consists in registering in the EF ocι file a new given network identity; this new identity being what the mobile phone registers in the list of prohibited networks following the sending by the SIM card of the "refresh" command. According to this embodiment, there is no introduction of the current network into the list of prohibited networks.

In another particular mode of implementation, the comparison by the SIM card of the identity of the current network is carried out periodically.

Brief description of the drawings

Other characteristics and advantages of the invention will become apparent from the following description given with reference to the accompanying drawings given by way of non-limiting examples. Figure 1 is a flow diagram of a method according to the invention.

FIG. 2 is a diagram representing part of the coverage areas of two networks belonging to two different operators. Description of an embodiment

The method according to the invention takes place according to several steps described below and illustrated by FIG. 1. In a first step 1, the SIM card of the mobile phone stores the location information MNCo, MCCo of the nominal network; the nominal network being the network belonging to the telecommunications operator to which the user of the mobile telephone is contracted. The first step of the process can take place during an initialization period, for example at the request of the user or for example when the mobile phone is started.

In a second step 2, the SIM card compares the location information MNC, MCC of the current network with the location information MNCo, MCCo of the nominal network. To retrieve the location information MNC, MCC of the current network copied by the mobile phone, the SIM card sends a command

"Location request".

In a third step 3, the SIM card fixes a specific location information “Status of the location update” contained in the file EF _L ocι at a determined value “network not authorized”. In a fourth step 4, the SIM card sends a “refresh” command to the mobile phone to warn it that the file EF _L ocι has been modified.

Following the reception of the "refresh" command, the mobile phone Ut the file EF _L ocι- The mobile phone detecting the reading "network not authorized" status, it tries to select a new network. As a priority, the mobile phone tries to select its nominal network. If the latter covers the area in which the mobile telephone is located, the selection of the nominal network is made, otherwise the selection relates to another network which covers the area. If the selection of the nominal network is successful, the EFL _OCI file contains the location information MNC ₀ , MCC _o of the nominal network. According to a particular embodiment, the method also consists in modifying the current location information, MNC and MCC, contained in the file EF _LOCI , by the SIM card, by reinitializing this location information MNC and MCC. This reinitialization consists in registering in the file EF _L ocι a new given network identity; this new identity being what the mobile phone registers in the list of prohibited networks following the sending of the "refresh" command. According to this realization, there is no introduction of the current network into the list of prohibited networks. This change is made in step 3.

The sequence of steps 2 to 4 can be done differently depending on the mode of implementation of the process. According to a first mode of implementation of the method, the SIM card sends a “location request” command at times t separated by a determined period Ti, for example equal to 30 minutes, to recover the location information MNC, MCC copied by the mobile phone before comparing them with the location information MNC ₀ , MCC ₀ of the nominal network. This mode occurs when the comparison in step 2 indicates that the networks are identical.

According to a second mode of implementation of the method, the mobile telephone notifies the SIM card each time that it modifies the location information. Upon receipt of the notification, the SIM card triggers the second step of the process and optionally the following depending on the result of the comparison. The second mode is generally excluded from the first mode.

According to a third mode of implementation of the method, steps 2 to 4 are linked at a rate T ₂ . This third mode can be triggered after a negative comparison. Indeed, when, during the second step, the comparison indicates that the current network is not the nominal network, it may be advantageous to try to re-select the nominal network at a high rate until the selection of the nominal network is successful.

FIG. 2 schematically represents a part of the coverage area of the nominal network of the first operator and a portion of the coverage area of the network of the second operator, these areas possibly in particular being located in a border area. The represented part of the nominal network coverage area corresponds to a cell 5 covered by a relay belonging to the network of the first operator. The represented part of the coverage area of the network of the second operator corresponds to a ceUule 6 covered by a relay belonging to the network of the second operator. The two cells 5, 6 have a zone 7 of overlap within which the coverage area of the nominal network has a hole 8.

When the mobile phone moves along the path 9 in cell 5 from the nominal network to hole 8, it attempts to contact another relay which covers hole 8. The network of the second operator covering hole 8, there is tilting of the mobile phone on the network provided that the operators have established a roaming agreement with each other. At the end of the changeover, the mobile telephone is registered in the list of mobile telephones managed by the network of the second operator and, the current location information MNC, MCC copied by the mobile telephone are equal to MNCi and MCC _t which correspond to coordinates of the second operator. SIM card detects change in location information after comparison that it performs between the current values MNC, MCC obtained by the command "request for location", and the nominal MNC ₀ , MCCo values that it stores. The SIM card modifies the EF _L ocι file. The mobile phone being informed of the modifications which have occurred in the EF _L ocι file by the "refresh" command, it detects the "network not authorized" state. This state triggers an attempt to select a network from the mobile phone; attempt which relates primarily to its nominal network. Thus, when the mobile phone leaves hole 8, while moving along the path 9 in the overlapping zone 7, contact with its nominal network can be established which allows it to re-select its nominal network as soon as he enters cell 5 of his coverage area.

Claims

1. Method for re-selecting a telecommunications network of a first operator, called nominal network, from networks belonging to different operators, called visited networks, each network being able to relay communications from a mobile telephone equipped with a SIM card present in their coverage area and each network having an identity (MNC, MCC), the mobile telephone copying the identity of the so-called current network with which it is registered at a given instant, characterized in that it includes the steps which consist in: memorizing (1) by the SIM card the identity (MNC ₀ , MCC ₀ ) of the nominal network,

- to compare (2) by the SIM card the identity (MNC, MCC) of the current network copied by the mobile phone to the identity (MNCo, MCCo) of the nominal network and, when the identities compared are different, to set ( 3) determined location information (“Status of the location update”) contained in a determined file (EF _LOCI ) at a determined value (“network not authorized”) and,

- to send (4) a command ("refresh") determined to the mobile phone signaling that the file (EF _L ocι) has been modified.

2. Re-selection method according to claim 1, characterized in that the fixing step (3) further consists of:

- to modify the identity (MNC, MCC) contained in the file (EF _L ocι) by the SIM card by resetting this identity (MNC, MCC) to a determined value.

3. Re-selection method according to one of claims 1 and 2, characterized in that the SIM card sends a determined command ("location request") at times t separated by a period (TA determined to recover l identity (MNC, MCC) of the current network copied by the mobile phone.

4. Re-selection method according to one of claims 1 and 2, characterized in that the SIM card triggers the comparison (2) upon receipt of a notification from the mobile phone signaling that the identity (MNC, MCC ) of the current network has been modified. Re-selection method according to one of claims 1 and 2, characterized in that, depending on the result of the comparison (2), the steps of fixing (3), sending (4) and comparison (2) are repeated at a specific period (T ₂ , Ti).