Abstract:
A method of selecting between telecommunication networks for at least two terminals capable of exchanging data in a first frequency band of a first telecommunication network with subscription and in a second frequency band of a second telecommunication network without subscription includes the steps of: estimating the relative distance between the two terminals; and switching the operation frequency of each of these two terminals from the first frequency band to the second frequency band if the distance between the two terminals is smaller than a predetermined value.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention is in the field of telecommunication, and it relates to a method and a device for allowing a mobile terminal to select between at least two radio access technologies: one technology providing access to a cellular telephone network, and another allowing access to an alternative network when it is shown that the recipient of a call is located close to the caller. More specifically, the invention relates to a method of selecting between telecommunication networks for at least two terminals capable of exchanging data in a first frequency band of a first telecommunication network with subscription and in a second frequency band of a second telecommunication network without subscription.  
           [0003]    2. Description of the Related Art  
           [0004]    Currently, two persons having a subscription with a cellular telephone carrier have to use their telephone service to make calls even when the distance that separates them is relatively short, for example a few dozen meters. This situation can take place in a railway station, on streets, or in an office building. However, there are gratuitous radio bands such as for example 2.4 GHz ISM (Industrial Scientific and Medical) band, which may be used within a limited geographical zone. These frequency bands generally requires a specific modem such as Bluetooth or Wi-Fi (Wireless Fidelity) modem characterized by their simplicity, low cost, and low energy consumption.  
         SUMMARY OF THE INVENTION  
         [0005]    Therefore, an object of the invention is to allow subscribers of a telecommunication network to use these alternative networks in limited zones such as for example within a company. In this way, economies in the communication costs may be achieved for the communication being made, especially when the volume of information to be exchanged is significant.  
           [0006]    The invention proposes a method of selecting between telecommunication networks for at least two terminals capable of exchanging data in a first frequency band of a first telecommunication network with subscription and in a second frequency band of a second telecommunication network without subscription.  
           [0007]    The method according to the invention comprises the steps of:  
           [0008]    estimating the relative distance between two terminals; and  
           [0009]    switching the operation frequency of each of these two terminals from the first frequency band to the second frequency band if the distance between the two terminals is smaller than a predetermined value R.  
           [0010]    Preferably, the switching to the second network also depends on the QoS (Quality of Service) assured by this second network.  
           [0011]    According to one embodiment of the invention, the estimating of the distance between the two terminals is performed by the network.  
           [0012]    According to another embodiment of the invention, the estimating of the distance between the two terminals is achieved by the calling terminal according to the following steps:  
           [0013]    The calling terminal receives its own geographical position P A  and the geographical position P B  of the called terminal from the network; and  
           [0014]    This calling terminal calculates the distance that separates it from the called terminal from the positions P A  and P B .  
           [0015]    According to a third embodiment of the invention, the estimating of the distance between the two terminals is achieved by the calling terminal according to the following steps:  
           [0016]    the called terminal requests its own geographical position P B  from the network and transmits position P B  to the calling terminal; and  
           [0017]    the calling terminal requests its own geographical position P A  from the network and calculates the distance that separates the calling terminal from the called terminal according to P A  and P B .  
           [0018]    The first network is either a UMTS (Universal Mobile Telecommunications System) network or a GSM (Global System for Mobile Communications) network, for example. The second network is one of Bluetooth, Wi-Fi and DECT (Digital European Cordless Telephone) networks, for example.  
           [0019]    The invention also relates to a device for selecting the operation frequency of at least two terminals, each comprising a radio access module for communicating in a first frequency band of a first telecommunication network with subscription and in a second frequency band of a second telecommunication network without subscription.  
           [0020]    The device according to the invention comprises:  
           [0021]    means for estimating the relative distance between two terminals; and  
           [0022]    means for switching the operation frequency of each of these two terminals from the first frequency band to the second frequency band if the distance between the two terminals is smaller than the radius R of the coverage of the second network.  
           [0023]    Preferably, the device according to the invention comprises means for calculating the distance between the two terminals according to the spatial coordinates of the terminals.  
           [0024]    The invention also relates to a mobile communication terminal comprising a radio access module for communicating with at least a second terminal in a first frequency band of a first telecommunication network with subscription and in a second frequency band of a second telecommunication network without subscription.  
           [0025]    The terminal according to the invention comprises a network selection module suitable for estimating the distance between the mobile terminal and the second terminal and for switching the operation frequency of said first terminal from the first frequency band to the second frequency band if the distance between the two terminals is smaller than the radius R of the coverage of the second network.  
           [0026]    In the present invention, since the second telecommunication network without subscription is selected instead of the first telecommunication network with subscription if the distance between the interlocutors is small, the communication costs between the interlocutors are remarkably reduced.  
           [0027]    The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate an example of the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    [0028]FIG. 1 is a block diagram illustrating a mobile terminal comprising a device according to the invention;  
         [0029]    [0029]FIG. 2 shows a block diagram illustrating an architecture of the terminal of FIG. 1 in a particular embodiment of the invention;  
         [0030]    [0030]FIG. 3 is a flowchart illustrating a first embodiment of the method according to the invention; and  
         [0031]    [0031]FIG. 4 is a flowchart illustrating a second embodiment of the method according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    In the following description, the terminals under consideration are mobile telephones whose hardware architecture conforms to a cellular telephony standard, for example GSM or UMTS. However, the invention can be applied to any user equipment (UE) capable of exchanging data.  
         [0033]    As can be seen in FIG. 1, these telephones comprise a stage  2  accommodating a plurality of applications that may be activated by a user from a presentation menu, a module  4  for handling call requests coming from the stage  2 , a network selection module  6 , a first modem  8  allowing access to a first frequency band of a first telecommunication network with subscription which is a GSM or UMTS network, and a second modem  10  allowing access to a second frequency band of a second telecommunication network without subscription. The second frequency band is preferably a free or gratuitous radio band such as 2.4 GHz ISM band.  
         [0034]    [0034]FIG. 2 schematically illustrates one embodiment of an architecture in which the second modem  10  appears as an application to the GSM/UMTS electronic card  12 .  
         [0035]    With reference to FIG. 2, the electronic card  12  supporting the GSM/UMTS access networks is connected, via an interface, to a Bluetooth modem  14 , a Wi-Fi modem  16 , and a DECT modem  18  respectively. These modems remain inactive so long as the GSM/UMTS electronic card  12  is active.  
         [0036]    In another embodiment (not shown), the modems  14 ,  16 , and  18  share with the electronic card  12  electronic components such as a microprocessor, a memory, and a radio frequency section.  
         [0037]    [0037]FIG. 3 is a flowchart schematically illustrating the functional role of the network selection module  6 . This module comprises a software program allowing the following tasks to be performed:  
         [0038]    1) When a caller terminal A wants to establish communication with a recipient terminal B, a call request is generated at the stage  2  at step  20 , and then transmitted to the module  4  for handling call requests.  
         [0039]    2) The software program generates a request, at step  22 , to access a locating service being subscribed with by at least one of the two parties in communication. This request is transmitted at step  24  to the GSM/UMTS cellular network that provides a service of locating subscribers.  
         [0040]    3) Upon receiving this call at step  26 , this locating service determines, at step  28 , the geographical coordinates of the terminals A and B and calculates, at step  30 , the distance D that separates the two terminals A and B. At step  32 , the caller A receives the calculated distance D and compares, at step  34 , the distance D with the value R representing the coverage of the second network that may be as much as several dozen meters.  
         [0041]    4) At this step, the network selection module  6  of the terminal A determines which frequency band is to be used for carrying out the next call in the following manner:  
         [0042]    If the calculated distance D is greater than R, the module  6  selects the GSM/UMTS network at step  36 ;  
         [0043]    If the calculated distance D is smaller than R, the module  6  selects the second network at step  38 .  
         [0044]    5) Once a telecommunication network is selected, the software program initiates a call according to the protocols associated with respective networks.  
         [0045]    In a variant embodiment in which the terminal A knows a priori the position of the terminal B, the selection between telecommunication networks may be made manually.  
         [0046]    Note that there is a great number of service providers that offer the possibility of finding out the distance that separates two mobile terminals in communication (see for example www.webraska.com and www.jlocationservices.com).  
         [0047]    [0047]FIG. 4 illustrates a second embodiment of the method of the invention in which the network carrier does not give the distance between terminals, giving only the coordinates of the caller.  
         [0048]    In this case, the terminal A establishes communication with the terminal B at step  40  via the UMTS/GSM network and requests the terminal B to ask for own position of the terminal B at step  42 , and then disconnects the communication at step  44 .  
         [0049]    Upon receiving the call from the terminal A at step  46 , the terminal B requests its own position from the network  6  at step  48 . Simultaneously, the terminal A requests its own position from the network at step  56 . The network estimates the position of the terminal A at step  58  and transmits the estimated position to the terminal A, which receives the position at step  59 . Then the network estimates the position of the terminal B at step  60  and transmits it to the terminal B. Upon receiving its own position at step  62  the terminal B establishes communication with the terminal A at step  64  via the UMTS/GSM network and provides the position of the terminal B to the terminal A, which receives it at step  66 .  
         [0050]    Estimating the distance from the positions of the terminals A and B:  
         [0051]    With the positions given by the geographical coordinates of terminals A and B, the mobile terminal A can estimate, at step  68 , the distance D that separates the terminal A from the terminal B according to a digitized electronic map stored formerly in the memory of the terminal A. It is only necessary then to locate the users in this map in order to determine the distance by means of an appropriate software program.  
         [0052]    The determined distance D is compared with the value R at step  69 :  
         [0053]    If the estimated distance D is greater than value R, the module  6  selects the GSM/UMTS network at step  70 ; and  
         [0054]    If the calculated distance D is smaller than value R, the module  6  selects the second network at step  72 .  
         [0055]    Once a telecommunication network is selected, the software program initiates a call according to the protocols associated with respective networks.