WO2007031651A1

WO2007031651A1 - Method and device for setting up a telephone link

Info

Publication number: WO2007031651A1
Application number: PCT/FR2006/002107
Authority: WO
Inventors: Jean-Pierre Daoudal
Original assignee: Orangefrance
Priority date: 2005-09-15
Filing date: 2006-09-14
Publication date: 2007-03-22
Also published as: EP1925180A1; FR2890821A1

Abstract

The invention concerns a method for setting up a telephone link whereby: if a second terminal is not within the coverage area of a private network, an interconnection module automatically determines (110) which complete number corresponds to the abbreviated number contained in the setup signal and acts (112) on a public network MSC center so that a HLR register of the public network is interrogated to determine whether the second terminal is within the public network coverage area using the determined complete number and not the abbreviated number, and in case of a positive determination, the setting up of the telephone link via both the private network and the public network equipment is ordered (120).

Description

METHOD AND DEVICE FOR ESTABLISHING A TELEPHONE LINK

The present invention relates to a method for establishing a telephone link, a module, an MSC center, a terminal, a program and a recording medium for this method. In the remainder of this description, the conventional terminology of the mobile telephone networks is used. For precise definitions of the terms used, it is for example possible to refer to the standards on GSM (Global System for Mobile Communication) or UMTS (Universal Mobile Communication System).

In the remainder of this description, the term "private network" is used to designate a private mobile network or PLMN (Private Land Mobile Network) and the term "public network" to designate a public mobile network or PLMN (Public Land Mobile Network) as these terms are defined in standards on mobile networks.

Private networks are built and operated by large companies to handle their internal communications and needs. These private networks are also called Private Enterprise Networks.

Private and public networks are essentially distinguished from one another by regulatory constraints. For example, the operator of a private network is not allowed to market its services to the public. In addition, for public networks, numbering plans are subject to the control of a national authority so that a telephone number assigned to a subscriber of a public network is not identical to that assigned to a subscriber. another subscriber of another public network. For example, numbering plans for public networks require that each subscriber have a complete ten-digit telephone number, the first two of which are "06". The telephone number whose structure conforms to the numbering plan of a public network is here called the "complete number".

This precaution, imposed by the national authority, then makes it possible to interconnect public networks and to establish telephone links between subscribers of different public networks.

Such a regulatory constraint does not exist for private networks. As a result, private network operators have for the most part developed numbering plans on their private networks which are completely incompatible with those of public networks. Typically, abbreviated telephone numbers are assigned to each subscriber or mobile terminal of a private network. For example, these abbreviated numbers are strictly less than ten digits and preferably between three and six digits. Such abbreviated numbers do not belong to the numbering plans of public networks and are therefore unusable on public networks.

On the other hand, from a structural point of view a private network can be identical to a public network. Therefore, the operation of a private network is very similar to the operation of a public network.

For example, when a first mobile terminal of a private network calls a second mobile terminal of the same private network, it proceeds as follows:

the first terminal transmits to a MSC (Mobile Services Switching Center) of the private network a signal for establishing the telephone link to the second terminal, this establishment signal containing the abbreviated number of the second terminal, and

in response to this establishment signal, the MSC of the private network interrogates a Home Location Register (HLR) of the private network to determine whether the second terminal is within the coverage area of the private network using the abbreviated number and not the full number, and

if so, the MSC center of the private network controls the establishment of the telephone connection between the first and second terminals.

This mode of operation must be compared to that of a public network in which a second mobile terminal present in the coverage area of the public network calls a first mobile terminal also in the coverage area of the same public network. In this case, it proceeds as follows:

the second terminal transmits to a Mobile Services Switching Center (MSC) of the public network a signal for establishing the telephone connection to the first terminal, this establishment signal containing the complete number of the first terminal, and in response to this a setup signal, if the first terminal is not within the coverage area of the private network, the public network MSC interrogates a public network HLR or VLR register to determine if the first terminal is connected to the network. within the coverage area of the public network using the complete number and not the abbreviated number of the first terminal, and

- if so, the MSC of the public network controls the establishment of the telephone connection between the first and second terminals. Thus, although technically similar, because of the regulatory differences and choices made by the operators of these private networks, most private networks are incompatible with public networks, so that these private networks operate autonomously and isolated from the networks. public. Thus, as soon as a mobile terminal of the private network is outside the coverage area of this private network, it is no longer reachable. The invention aims to overcome this disadvantage by proposing a method for establishing a telephone connection between a first mobile terminal present in the coverage area of a private network and a second mobile terminal of this private network but located outside. the coverage area of the private network.

The subject of the invention is therefore a method for establishing a telephone connection between these two mobile terminals via a private network interconnected to a public network in which the second terminal is identified by an abbreviated telephone number on the telephone. the private network and by a complete telephone number on the public network, the abbreviated number not being part of the numbering plan of the public network and in which, when the first terminal calls the second terminal: if the second terminal is not located within the coverage area of the private network, an interconnection module automatically establishes the complete number corresponding to the abbreviated number contained in the establishment signal and acts on an MSC center of the public network so that a HLR or VLR register

(Visitor Location Register) of the public network is queried to determine if the second terminal is within the coverage area of the public network using the complete number established and not the abbreviated number, and

- if so, the establishment of the telephone connection between the first and second terminals via equipment of both the private network and the public network is controlled.

In the above method, by automatically setting the complete number of the second terminal from its abbreviated number, the second terminal becomes localizable on the public network, which allows the establishment of a telephone connection between the first and second terminals. and second terminals, while only the abbreviated number of the second terminal has been transmitted by the first terminal. The invention also relates to a method of establishing a telephone connection between these two terminals via a private network interconnected to a public network in which the first terminal is identified by a short telephone number on the private network and by a complete telephone number on the public network, the abbreviated number not being part of the numbering plan of the public network and in which, when the second terminal calls the first terminal: - if the first terminal is located within the coverage area of the public network, an interconnection module establishes the abbreviated number corresponding to the complete number contained in the establishment signal and acts on an MSC center of the private network so that an HLR or VLR register of the private network is queried to determine if the first terminal is within the coverage area of the private network in use reading the abbreviated number established and not the complete number, and - if so, the establishment of the telephone connection between the first and second terminals via equipment of both the private network and the public network is controlled. In the above method, by setting the abbreviated number of the first terminal from its full number, the first terminal becomes localizable on the private network, which allows the establishment of a telephone connection between the first and the first terminal. second terminals, while the first terminal is a terminal of the private network located in the coverage area of this private network.

The embodiments of the two above methods may include one or more of the following features: - the interconnection module is implemented in the MSC center of the private network or in the MSC center of the public network;

it comprises a step of automatic selection of the IMSI identifier to be used during the establishment of the telephone link according to the coverage area in which the terminal is located, this step being performed so as to systematically select the first IMSI identifier when the terminal is in both the coverage area of the private network and the public network; it comprises a step of automatically transforming a dialed number dialed on the second terminal into a complete number and a step of transmitting the signal for establishing the telephone link to the MSC center of the public network, this signal containing this complete number only if the second terminal is in the coverage area of the public network.

These embodiments of the above methods also have the following advantages: the use of a common interconnection module implemented in an MSC center makes it possible to avoid having to implement the functionalities of this interconnection module in each of the terminals; the selection module makes it possible to preferentially select the private network, where possible, so as to limit the costs of establishing a telephone link; and

the step of automatically transforming the abbreviated number into a complete number makes it possible to make the use of the second terminal transparent for the subscriber even when this second terminal is outside the coverage area of the private network.

The invention also relates to an interconnection module adapted to be implemented in the above methods of establishing a telephone link in which:

- if the second terminal is not in the coverage area of the private network, the interconnection module is able to automatically establish which is the complete number corresponding to the abbreviated number contained in the establishment signal and to act on a center MSC of the public network, so that a public network HLR or VLR register is polled to determine if the second terminal is in the coverage area of the public network using the full number established and not the abbreviated number; and

the interconnection module is able to determine which is the abbreviated number corresponding to the complete number contained in the establishment signal and to act on an MSC center of the private network, so that an HLR or VLR register of the network private party to be interviewed to determine if the first terminal is within the W

8 coverage of the public network using the abbreviated number and not the full number.

The invention also relates to a MSC (Mobile Services Switching Center) of a private or public network comprising the interconnection module above.

Another subject of the invention is a mobile terminal capable of being implemented in the above method of establishing a telephone link, this terminal comprising: a memory containing a first IMSI identifier (International Mobile Subscriber Identity) enabling to identify the subscriber of the terminal on the private network and a second identifier IMSI for identifying the subscriber of the terminal on the public network, and - an automatic selection module of the identifier IMSI to be used during the establishment of a telephone connection according to the coverage area within which the second terminal is located, this selection module being adapted to systematically choose the first IMSI identifier when the second terminal is both in the zone of coverage of the private network and the public network.

The embodiments of this mobile terminal may comprise the following characteristic: it comprises a transformation module able to automatically transform a dialed number dialed on the terminal into a complete number and to transmit a signal for establishing the telephone link to the center MSC of the public network, this establishment signal containing the complete number and not the abbreviated dialed number only if the second terminal is within the coverage area of the public network.

The invention also relates to a computer program and an information recording medium including instructions for carrying out the above method of establishing a telephone link, when these instructions are executed by an electronic computer. The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings in which:

FIG. 1 is a schematic illustration of the architecture of a system for establishing a telephone connection between mobile terminals of a private network; and FIG. 2 is a flowchart of a method for establishing a telephone link between the mobile terminals of FIG.

Figure 1 shows a system 2 for establishing a telephone link between mobile terminals.

In the following description, the functions and equipment of the system 2 well known to those skilled in the art are not described in detail.

Here, the system 2 comprises a private network 4 and a public network 6. The networks 4 and 6 are, for example, GSM networks or UMTS networks. Network 4 can also be a private network compatible with mobile networks ^• such as a TETRA network (see, for example, the following website for more information on TETRA: http://www.olnet.com/ editorial / 259420 / telecommunications / wireless-networks-direct-and-secured /).

Network 4 comprises base stations or BTS stations ("Base station") connected to BSC controllers

("Base Station Controller"). To simplify FIG. 1, only two BTS stations 10 and 12 of the network 4 connected to a BSC controller 14 have been represented. Each BTS station defines a coverage area in which a mobile terminal can make or receive a call.

Here, the overall coverage area of the network 4 is represented by a wavy line on which the arrow with the reference 4 points.

The network 4 also includes a Mobile Services Switching Center (MSC) 16 connected to a Home Location Register (HLR) 18 and to a Visitor Location Register (VLR) 20.

The registers 18 and 20 are connected to the center 16 via a signaling network specific to the network 4. Such a signaling network is only used to transport network management commands 4 and not to carry voice data. exchanged between two mobile terminals.

The controller 14 is connected to the center MSC 16.

The registers HLR and VLR are those defined, for example, in the GSM standard. The network 4 also comprises mobile terminals capable of establishing telephone links between them using only the equipment of the network 4. By way of illustration, three mobile terminals 24, 26 and 28 of the network 4 are shown in FIG. terminal 24 is only in the coverage area of station 10 and terminal 26 is in the coverage area of station 12. Terminal 28 is outside the coverage area of network 4 and within the area 6. For example, the terminals 24, 26 and 28 are identical, so that only the terminal 24 will be described here in detail.

The terminal 24 comprises a memory 30 containing an identifier IMSI (International Mobile Subscriber Identity) 32 to identify a subscriber network 4. Typically, the memory 30 is a SIM card (Subscriber Identity Module).

The network numbering plan 4 defines the structure of the abbreviated telephone numbers that can be used on this network 4. For example, here each abbreviated number has the following structure: QMCDU, where each letter corresponds to a digit between 0 and 9.

The network 6 has a structure similar to that of the network 4. To simplify FIG. 1, only the following devices of the network 6 are represented:

two base stations 40 and 42, a BSC controller 44 connected to the two base stations 40 and 42,

an MSC center 46 connected to the controller 44, and

an HLR register 48 and a VLR register 50 connected to the center 46 via a signaling network specific to the network 6.

The area of coverage of the network 6 is also represented by a wavy line designated by the end of the arrow bearing the reference 6.

Here, the base station 40 is located near the base station 12, so that the terminal 26 is in both the coverage area of the station 12 and the station 14. Thus, the coverage areas networks 4 and 6 at least partially overlap in a region R. The terminal 28 is only in the coverage area of the station 42.

The network numbering plan 6 is subject to the constraints of the national authority. For example, the network numbering plan 6 defines that the complete number of The telephone assigned to each subscriber of the network 6 is formed of ten digits whose first four digits are, for example "06 AB", or the letters A and B each represent a predetermined digit assigned to the operator of the network 6. In addition, here, it will be assumed in the remainder of this description, that the range of complete numbers between "06 ABP 0000" and "06 ABP 99999" has never been used, where P is a predetermined digit.

The numbering plan of the network 6 is incompatible with that adopted for the network 4, since the network 6 requires that each complete number has ten digits, while the abbreviated numbers of the network 4 have only five digits. Therefore, the register 48 does not locate a terminal from a short code, since it is only able to manage complete numbers in accordance with the network numbering plan 6.

To allow the establishment of a telephone connection between, for example, the terminal 28 and the terminal 24 or 26, the system 2 has the characteristics described below.

Firstly, the networks 4 and 6 are interconnected via a bi-directional information transmission link 60 also called "interconnection". The link 60 connects the centers 16 and 46.

The center 16 includes an interconnection module 62 capable of establishing a complete number from an abbreviated number and vice versa.

The memory 30 of each terminal comprises a second identifier IMSI 64 able to identify the subscriber on the network 6. The identifier 64 thus allows the establishment of a telephone connection with another terminal using only the equipment of the network 6. Each terminal also comprises a module 66 for selecting the identifier to be used and a module 68 for transforming an abbreviated number into a complete number. Details of the functions of the modules 66, 68 and 62 will appear on reading the description given with reference to FIG. 2.

The modules 66 and 68 are, for example, software modules executed by an electronic computer 70 of the terminal 24. Typically, the computer 70 is made from a conventional programmable computer capable of executing instructions recorded on a recording medium 72. For this purpose, the support 72 includes instructions for executing the method of FIG. 2, when these instructions are executed by the computer 70.

Similarly, for example, the module 62 is a software module executed by an electronic computer 74 of the center 16. The computer 74 is here made from a conventional programmable computer capable of executing instructions recorded on a recording medium. 76. For this purpose, the support 76 includes instructions for executing the method of FIG. 2, when these instructions are executed by the computer 74. The operation of the system 2 will now be described with reference to FIG. 2. .

Initially, during a step 90, a range of the numbering plan of the network 6 is reserved for the subscribers of the network 4. For example, here, the range of telephone numbers between "06 ABP 00000" and "06 ABP 999999" is reserved.

During the operation of the networks 4 and 6, each base station transmits permanently, during a step 92, a identifier of the network to which the base station that transmits it belongs.

In a step 94, the terminals that are in the coverage area of the network 4 or the network 6 receive this identifier and transmit it to their respective selection module.

In a step 96, each selection module 66 determines from the network identifier received in which (s) coverage area (s) it is located. In the case where the terminal is only in the coverage area of the network 4 or in a recovery area such as the region R, then the module 66 proceeds to a step 98 in which it automatically selects the IMSI identifier 32. Conversely, if the terminal is only in the coverage area of the network 6, the selection module 66 then automatically selects, during a step 100, the IMSI identifier 64.

Thus, in the particular case of FIG. 1, the terminals 24 and 26 select the IMSI identifier 32, while the terminal 28 selects the IMSI identifier 64.

Then, after step 98, in the case where the terminal is in the coverage area of the network 4, a subscriber dials, in a step 102, a short code of another terminal. For example, in the remainder of this description, it is assumed that the terminal 26 is used by the subscriber to dial.

When the terminal 26 seeks to establish a telephone connection via the network 4, the subscriber is identified on the network 4 using the IMSI 32, so that the network 4 recognizes it as a subscriber and authorizes the establishment through its equipment a telephone connection from the terminal 26.

In a step 104, the terminal 26 transmits in response to this numbering, a telephone link establishment signal containing the compound abbreviated number. This signal is received by the base station 12 and then routed to the center 16 using only the equipment of the network 4.

During a step 106, in response to the reception of this establishment signal, the center 16 interrogates the HLR register 18 to determine if the terminal corresponding to this abbreviated number is in the coverage area of the network 4. When In step 106, the interrogation request is transmitted via the signaling network connecting the register 18 to the center 16.

Following this interrogation, if it turns out that the terminal corresponding to the abbreviated number is in the coverage area of the network 4, then, in a step 108, the center 16 controls the establishment of the telephone connection between the terminal 26 and its recipient. By

for example, if the recipient is the terminal 24, in step 108, the center 16 controls the establishment of the telephone link between the terminals 26 and 24. In step 108, only the equipment of the network 4 is used to establish this telephone link, so that such a call is free for the operator of the network 4.

Otherwise, that is, if the recipient's terminal corresponding to the abbreviated number is not in the coverage area of the network 4, then, in a step 110, the interconnection module 62 establishes from the abbreviated number contained in the establishment signal, the corresponding complete number. This situation corresponds, for example to the case where the called terminal is the terminal 28. Specifically, in step 110, here the interconnection module 62 builds the complete number from the abbreviated number QMCDU by adding the number string "06 ABP" to the beginning of the abbreviated number. Then, during a step 112, the interconnection module acts on the center 46 so that the HLR register 48 is interrogated to determine if the terminal 28 is in the coverage area of the network 6.

More specifically, during step 112, the module 62 replaces, during an operation 114, the abbreviated number contained in the establishment signal by the complete number established in step 110. Then, during a operation 116, the module 62 controls the transmission of the establishment signal thus modified to the center 46 via the link 60.

At the end of step 112, during a step 118, the center 46 interrogates via a signaling network, the register 48 to determine if the terminal 28 is inside the coverage area of the network 6. If so, during a step 120, the centers 16 and 46 then cooperate to control the establishment of a telephone connection between the terminals 26 and 28 via equipment of the network 4 and the network 6.

In the opposite case, that is to say if the terminal corresponding to the abbreviated number is not inside the coverage area of the network 6, then during a step 122, the telephone link n is not established or the terminal 28 is searched on another public network interconnected to the network 6, so as to establish the telephone connection through the networks 4 and 6 and this other public network. The other public network is, for example, a national or foreign public network. To illustrate what happens after step 100, it will now be assumed that the terminal 28 is used to call the terminal 24.

After step 100, the user subscriber of the terminal 28 dials an abbreviated number. Therefore, in a step 130, the transformation module 68 automatically transforms the dialed number dialed into a complete number. For example, the module 68 adds the prefix "06 ABP" to the abbreviated number QMCDU compound ^'by the subscriber. After, during a step 132, the terminal 28 transmits a signal for establishing a telephone link containing the complete number established during step 130. In step 132, the terminal 28 uses the identifier IMSI 64 to identify the subscriber with the network 6, which allows the routing of the establishment signal to the center 46 via the station 42 and the controller 44.

During a step 140, the center 46 transmits the establishment signal containing the complete number to the center 16 via the link 60. Preferably, the step 140 is only performed if the complete number of the called terminal is in the range of telephone numbers reserved for network subscribers 4.

In response to receiving this setup signal from link 60, in step 142, module 62 sets the abbreviated number corresponding to the complete number contained in the received setup signal. Here, for example, the module 62 deletes the prefix "06 ABP" from the complete number to obtain the abbreviated number.

Then, during a step 144, the module 62 acts on the center 16 so that it interrogates the HLR register 18 by using the abbreviated number established in the step 142. In a step 146, the center 16 thus interrogates the HLR register 18 using the abbreviated number and not the complete number, so as to determine if the called terminal is in the coverage area of the network 4. If yes in a step 148, the centers 16 and 46 then cooperate to control the establishment of the telephone connection between the terminal 28 and the called terminal. In step 148, the telephone link is established using equipment of both network 4 and network 6.

In the opposite case, that is to say if the called terminal is not inside the coverage area of the network 4, then during a step 150, the center 46 interrogates the register HLR 48 for determine if the called terminal is in the coverage area of the network 6. In step 150, only the complete number is used and not the abbreviated number.

If so, that is to say if the called terminal is in the coverage area of the network 6, then the center 46 controls, during a step 152, the establishment of the telephone connection between the terminal 28 and the called terminal. In step 152, only the network devices 6 are used to establish this telephone link. In the opposite case, that is to say if the called terminal is not in the coverage area of the network 6 then, during a step 154, the telephone connection is not established or the mobile terminal is Thus, by the above method, the terminals 24 and 26 can call the terminal 28 using an abbreviated number and vice versa.

The fact that step 146 precedes step 150 gives priority to establishing a telephone link to the times via network equipment 4 and 6, when the called terminal is in the region R.

Many other embodiments of system 2 and the above method are possible. For example, the interconnection module 62 may use a look-up table associating each abbreviated number with the corresponding complete number rather than using a concatenation or truncation operation of a digital string as described above. The coverage area of the network 6 can completely encompass the coverage area of the network 4. On the other hand, the coverage areas of the networks 4 and 6 can be completely disjoint.

The interconnection module 62 has been described as being implemented in the center 16. In a variant, this module 62 can be implemented in the center MSC 46. In this case, the center 16 is adapted to transmit the establishment signal containing the abbreviated number to the center 46 when the called terminal is not in the coverage area of the network 4. The interconnection module then replaces the abbreviated number contained in the establishment signal received by the complete number, which allows query the HLR 48 register using the complete number. In the case of a call made from a terminal outside the coverage area of the network 4, the interconnection module implemented in the center 46 is adapted to replace the complete number contained in the received establishment signal. by the abbreviated number before returning the establishment signal to the center 16 via the link 60.

Finally, it will be noted that if the terminal 28 moves from the cell managed by the station 42 to the cell managed by the station 40, the current telephone connection is not interrupted and the cell change is effected. according to the so-called "Hand Over" procedure. On the other hand, if the terminal 28 leaves the cell managed by the station 40 to enter the cell managed by the station 10, the current telephone connection is interrupted. In other words, the transition from a coverage area of the network 6 to an area exclusively covered by the network 4 is achieved by the so-called "roaming" procedure.

As a variant, the interconnection module may be implemented partly in the center 16 and partly in the center 46. For example, the functionalities of the interconnection module used to establish a telephone connection from the terminal 24 to the terminal 28 are implemented. in the center 16, while the functionalities of the interconnection module used to establish the telephone connection from the terminal 28 to the terminal 24 are implemented in the center 46.

Alternatively, the interconnection module acts on the MSC to interrogate the VLR, in addition to or instead of the HLR to determine if the recipient's terminal is in that coverage area.

Claims

A method of establishing a telephone link between first and second mobile terminals via a private mobile network PLMN

Network) interconnected to a public network PLMN (Public Land

Mobile Network), the second terminal being identified by an abbreviated telephone number on the private network and by a complete telephone number on the public network, the abbreviated number not forming part of the public network numbering plan, in which:

the first terminal transmits (at 104) to a mobile service switching center (MSC) of the private network a signal for establishing the telephone connection to the second terminal, this establishment signal containing the abbreviated number of the second terminal, and

in response to this establishment signal, the MSC center of the private network interrogates (in 106) a Home Location Register (HLR) of the private network to determine if the second terminal is within the coverage area of the network using the abbreviated number and not the complete number, and

- if so, the MSC center of the private network controls (in 108) the establishment of the telephone connection between the first and second terminals, characterized in that: if the second terminal is not inside the In the coverage area of the private network, an interconnection module automatically establishes (at 110) the complete number corresponding to the abbreviated number contained in the establishment signal and acts (at 112) on an MSC center of the public network so as to what a HLR or VLR register (Visitor Location Register) of the network the second terminal is within the coverage area of the public network using the full number established and not the abbreviated number, and - if so, the establishment of the telephone link between the first and second terminals via equipment of both the private network and the public network is controlled (at 120).

A method of establishing a telephone link between first and second mobile terminals via a Private Land Mobile Network (PLMN) interconnected to a Public Land Mobile Network (PLMN), the first terminal being identified by a telephone number abbreviated on the private network and by a complete telephone number on the public network, the abbreviated number not being part of the public network numbering plan, wherein:

the second terminal transmits (at 132) to a mobile service switching center (MSC) of the public network a signal for establishing the telephone connection to the first terminal, this establishment signal containing the complete number of the first terminal, and in response to this setup signal, if the first terminal is not within the coverage area of the private network, the MSC of the public network interrogates (at 150) a public network register HLR or VLR for determine if the first terminal is within the coverage area of the public network using the complete number and not the abbreviated number of the first terminal, and

- if so, the MSC center of the public network controls (at 152) the establishment of the telephone connection between the first and second terminals, characterized in that: if the first terminal is not within the coverage area of the public network, an interconnection module sets (at 142) which is the abbreviated number corresponding to the complete number contained in the establishment signal and acts ( 144) to an MSC of the private network so that a private network HLR or VLR register is polled to determine if the first terminal is within the coverage area of the private network using the abbreviated number established and not the full number, and

- if so, the establishment of the telephone connection between the first and second terminals via equipment of both the private network and the public network is controlled (in 148).

3. Method according to any one of the preceding claims, characterized in that the interconnection module is implemented in the MSC center of the private network or in the MSC center of the public network.

4. Method according to any one of the preceding claims wherein at least one of the terminals comprises a memory containing a first identifier International Mobile Subscriber Identity (IMSI) for the identification of a subscriber on the private network and a second identifier. IMSI for identifying a subscriber on the public network, characterized in that it comprises a step (98, 100) of automatic selection of the IMSI identifier to be used during the establishment of the telephone link as a function of the area of coverage in which the terminal is located, this step being performed so as to systematically choose the first IMSI identifier when the terminal is both in the coverage area of the private network and the public network.

5. Method according to any one of claims 2 to 5, characterized in that it comprises a step (150) of automatic transformation of an abbreviated dialed number on the second terminal into a complete number and a step of transmitting the signal. of establishing the telephone connection to the MSC center of the public network, this signal containing this complete number only if the second terminal is in the coverage area of the public network.

Interconnection module (62) adapted to be implemented in an establishment method according to any one of claims 1 and 3 to 5, characterized in that if the second terminal is not in the Within the coverage area of the private network, the interconnection module is able to automatically establish which is the complete number corresponding to the abbreviated number contained in the establishment signal and to act on an MSC center of the public network, so as to an HLR or VLR register of the public network is polled to determine if the second terminal is in the coverage area of the public network using the complete number established and not the abbreviated number.

Interconnection module (62) adapted to be implemented in an establishment method according to any one of Claims 2 to 5, characterized in that the interconnection module is able to determine the number an abbreviation corresponding to the complete number contained in the establishment signal and to act on an MSC center of the private network, so that an HLR or VLR register of the private network is interrogated to determine if the first terminal is inside. the coverage area of the private network using the abbreviated number and not the complete number.

8. A Mobile Services Switching Center (MSC) of a Private Land Mobile Network (PLMN) or of a Public Land Mobile Network (PLMN), characterized in that it comprises a module (62) for interconnections according to claim 6 or 7.

Mobile terminal adapted to be implemented in a method according to any one of claims 1 to 5, characterized in that the terminal comprises:

a memory (30) containing a first International Mobile Subscriber Identity (IMSI) identifier making it possible to identify the subscriber of the terminal on the private network and a second identifier IMSI making it possible to identify the subscriber of the terminal on the public network, and a module (66) for automatic selection of the IMSI identifier to be used when establishing a telephone link as a function of the coverage area inside which the second terminal is located, this selection module being clean systematically selecting the first IMSI identifier when the second terminal is in both the coverage area of the private network and the public network.

10. Terminal according to claim 9, characterized in that it comprises a transformer module (68) capable of automatically transforming an abbreviated dialed number on the terminal into a complete number and transmitting a signal for establishing the telephone link to MSC center of the public network, this establishment signal containing the complete number and not the abbreviated dialed number only if the second terminal is within the coverage area of the public network.

11. Computer program, characterized in that it comprises instructions for the implementation of a method of establishing a telephone link according to any one of claims 1 to 5, when these instructions are executed by an electronic calculator.

12. Information recording medium, characterized in that it comprises instructions for implementing the method of establishing a telephone link according to any one of claims 1 to 5, when these instructions are executed. by an electronic calculator.