Abstract:
A method in a mobile station comprises searching for WLANs with a WLAN module implemented in the mobile station; communicating information about the WLANs found in the previous step to an administration unit configured to provide WLAN access data for a plurality of WLANs; receiving WLAN access data for at least one of the WLANs for which information was sent to the administration unit in the previous step; and accessing one of the WLANs using the WLAN access data provided by the administration unit. The mobile station communicates with the administration unit via a cellular communications network operated by a mobile network operator (MNO). The MNO can remotely manage the WLAN access data available on the mobile station with the administration unit and to which available WLANs the mobile station can attach.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to mobile communications in general and in particular to methods and devices for accessing a wireless local area network. 
       BACKGROUND OF THE INVENTION 
       [0002]    The rapidly growing demand of mobile stations for bandwidth can challenge the infrastructure of current cellular communications networks. This poses a problem for mobile network operators (MNO) who want to provide mobile communications with a certain standard of quality. In addition to being able to communicate via a cellular communications network most modern mobile stations, in particular smartphones, are equipped with a WLAN module or card that enables a mobile station to communicate via a wireless LAN (WLAN) with web servers or other end stations connected to the Internet. As WLANs are becoming more and more ubiquitous, a mobile station will be generally within the communication range of the base stations of several cellular communications networks as well as of the access points of several WLANs. Thus, WLANs, in principle, offer the potential to offload data traffic from a congested cellular communications network to a less congested WLAN, for instance, during events where a lot of people come together within bounded spatial areas, such as rock concerts, sports events and the like. Under such circumstances it would desirable for a MNO to be able to transfer and manage services for his mobile users to other communication networks, such as WLANs. 
         [0003]    [03] In order to access a specific WLAN a mobile station generally will require specific WLAN access data or settings that allow the access point of the WLAN to identify and authenticate the mobile station to provide the mobile station with access to the Internet. Such WLAN access data could be pre-stored in the mobile station, for instance, during the manufacturing or personalization process thereof. However, as network access mechanisms and WLAN operators have proliferated, it has become increasingly likely that users will encounter networks for which no pre-configured settings are available. Thus, users can have difficulty in determining which network they are able to connect to and how to authenticate to that network. Moreover, for security reasons it could be desirable for a mobile network operator to be able to manage or at least monitor to which WLAN a mobile station&#39;s data traffic is offloaded. 
         [0004]    Thus, the problem addressed by the present invention is to provide improved methods and devices for accessing a wireless communications network, in particular a WLAN, by means of a mobile station configured to communicate via a cellular communications network. 
       SUMMARY OF THE INVENTION 
       [0005]    This object is achieved according to the present invention by the subject-matter of the independent claims. Preferred embodiments of the invention are defined in the dependent claims. 
         [0006]    Generally, the present invention is based on the idea to keep up-to-date WLAN access data for a plurality of WLANs that a mobile station might encounter within an administration unit, preferably an administration server operated by a mobile network operator (MNO), and to provide the mobile station on-demand with WLAN access data for selected ones of the plurality of WLANs. Preferably, the mobile station can communicate with the administration server via a public mobile land network (PLMN) operated by the MNO. This allows the MNO to remotely manage the WLAN access data that is available on a mobile station by means of the administration server and, thus, to which available WLANs the mobile station can attach. 
         [0007]    More specifically, according to a first aspect the invention is directed to a method for accessing a wireless local area network by means of a mobile station that is configured to communicate via a cellular communications network. The method comprises the following steps in the mobile station: searching for available WLANs by means of a WLAN module implemented in the mobile station; communicating information about the WLANs found in the previous step to an administration unit configured to provide WLAN access data for a plurality of WLANs; receiving WLAN access data for at least one of the WLANs for which information was sent to the administration unit in the previous step; and accessing one of the WLANs for which WLAN access data has been provided by the administration unit. 
         [0008]    According to a second aspect the invention is directed to a method for providing a mobile station with WLAN access data. The method comprises the following steps in the administration unit: receiving from a mobile station information about available WLANs in the vicinity of the mobile station that have been found by means of a WLAN module implemented in the mobile station; obtaining WLAN access data for at least one of the WLANs for which information was received by the administration unit from the mobile station in the previous step; and sending the WLAN access data to the mobile station. 
         [0009]    According to a third aspect the invention is directed to a mobile station that is configured to communicate via a cellular communications network. The mobile station is configured and/or comprises respective means for: searching for available WLANs by means of a WLAN module implemented in the mobile station; communicating information about the discovered available WLANs to an administration unit configured to provide WLAN access data for a plurality of WLANs; receiving WLAN access data for at least one of the WLANs for which information was sent to the administration unit; and accessing one of the WLANs for which WLAN access data has been provided by the administration unit. 
         [0010]    According to a fourth aspect the invention is directed to an administration unit, preferably an administration server, that is configured and/or comprises respective means for: receiving from a mobile station information about available WLANs in the vicinity of the mobile station that have been found by means of a WLAN module implemented in the mobile station; obtaining WLAN access data for at least one of the WLANs for which information was received by the administration unit from the mobile station; and sending the WLAN access data to the mobile station. 
         [0011]    According to preferred embodiments of the invention, the mobile station comprises a secure element for securely storing data that allows the mobile station to attach to and communicate with a cellular communications network. In the case of a cellular communications network in the form of a Public Land Mobile Network (PLMN) implemented according to the GSM standard, the secure element preferably includes an International Mobile Security Identity (IMSI) and/or an authentication key Ki for authenticating the secure element relative to the PLMN. The secure element can be configured to be removably inserted into the mobile station or, alternatively, embedded therein. According to preferred embodiments of the invention, the secure element is implemented as a subscriber identity module (SIM), UICC, USIM, R-UIM or ISIM. 
         [0012]    Preferably, the mobile station communicates with the administration unit for obtaining WLAN access data via a cellular communications network, such as GSM, UMTS, LTE, CDMA, and the like. Preferably, the communication between the mobile station and the administration unit via the cellular communications network is done by SMS protocol (Short Message Service), USSD protocol (Unstructured Supplementary Service Data) or a similar text message protocol. 
         [0013]    Preferably, the WLAN module is part of the secure element of the mobile station for securely storing data that allows the mobile station to attach to and communicate with a cellular communications network. This embodiment is particularly advantageous, as any sensitive data for attaching to a WLAN or to a cellular communications network is confined to the secure element. 
         [0014]    According to preferred embodiments of the invention, the mobile station is configured to access a WLAN established by an access point that is configured according to the standard IEEE 802.11 and/or one or more of its sub-standards, such as IEEE 802.11b, 802.11a, 802.11g, 802.11i, 802.11n, and 802.11ac (such WLANs are also known as WiFi networks). Alternatively, the WLAN could be a wireless LAN operated according to the Bluetooth standard (IEEE 802.15.1) or the WiMAX standard (IEEE 802.16). 
         [0015]    Preferably, the administration unit is configured to provide the mobile station with a preferred WLAN or a prioritized list of WLANs selected out of the list of available WLANs such that the mobile station will try to attach to the available WLANs according to the prioritized list. Preferably, the administration unit is configured to create this prioritized list of WLANs on the basis of selection rules implemented in the administration unit. By means of this prioritized list the administration unit can cause the mobile station to attach to specific WLANs having, for instance, a high data throughput and/or operated by a party known to the MNO or the MNO itself. Preferably, the administration unit is configured, when selecting a preferred WLAN or creating a prioritized list of preferred WLANs, to take into account the technical capabilities of the mobile station. Information about the technical capabilities of the mobile station could be stored in the administration unit or transmitted from the mobile station to the administration unit along with the information about available WLANs. 
         [0016]    According to preferred embodiments of the invention, WLAN access data to be provided by the administration unit to the mobile station can be retrieved from a database of the administration unit storing up-to-date WLAN access data for a plurality of WLANs. Alternatively or additionally, the administration unit can try to retrieve WLAN access data, for instance, WLAN access data that is not available in the administration unit&#39;s database, from the access points of such WLANs or from other servers providing for such services over the Internet. 
         [0017]    Preferably, the step in the mobile station of searching for available WLANs by means of the WLAN module implemented in the mobile station can comprise the step of actively probing for available WLANs or, alternatively, the step of passively scanning for available WLANs. In an active probing process the mobile station could send a broadcast signal to cause any available WLAN access points within the communication range of the mobile station to transmit a beacon frame including information about the respective WLAN. In a passive scanning process the mobile station could simply listen for beacon frames being periodically transmitted by access points of WLANs within the vicinity of the mobile station. 
         [0018]    According to preferred embodiments of the invention, an application is implemented on the mobile station, preferably on its secure element, configured to cause the mobile station to perform the steps of the method according to the above-described first aspect of the invention. In particular, the application is configured to trigger the search for available WLANs by means of the WLAN module of the mobile station, to communicate information about the discovered WLANs to the administration unit, and to access one of the WLANs using the WLAN access data provided by the administration unit. 
         [0019]    Preferably, the application could trigger the search for available WLANs in response to the following events: terminal events, such as power-on, the expiration of a timer, and/or the discovery of a new WLAN. Alternatively or additionally, the search for new WLANs and/or the transmission of information about new WLANs to the administration unit can be triggered by the administration unit or the PLMN. For instance, in case the data traffic within the cell of the PLMN the mobile station  12  is located in is higher than a pre-defined threshold, the administration unit or the PLMN can cause the mobile station to search for available WLANs that might be suitable for offloading data traffic. Alternatively, the mobile station could be configured to periodically search for new available WLANs within the vicinity of the mobile station and to communication about new available WLANs to the administration unit once these are discovered. 
         [0020]    Moreover, the application, preferably implemented within the secure element, can be configured to cause the display of a message on a display of the mobile station informing the user of the mobile station about the preferred WLAN or the prioritized list of WLANs selected by the administration unit. The application could be further configured such that the user of the mobile station has to confirm the attachment to the preferred WLAN or one of the WLANs from the prioritized list of WLANs selected by the administration unit, before the mobile station can try to attach thereto. 
         [0021]    Preferably, the information about the WLANs communicated to the administration unit comprises for each respective WLAN a WLAN specific identifier, such as the SSID (Service Set Identifier), the signal strength of the WLAN, quality of service capabilities (as defined by IEEE 802.11e), and/or information about the employed security mechanism, such as WEP, WAP or WAP2. Preferably, the mobile station is configured to extract this information from the beacon frames regularly emitted by the respective access points of the available WLANs. 
         [0022]    According to preferred embodiments of the invention, the WLAN access data provided from the administration unit to the mobile station comprises for each respective WLAN a WLAN specific identifier, such as the SSID (Service Set Identifier), a user name, a user password and/or any secret keys required for successfully attaching to a respective WLAN. Preferably, this WLAN access data is sent from the administration unit over the PLMN to the mobile station in encrypted form and is decrypted within the secure element, as is the case, for instance, according to the GSM standard. This is advantageous, in particular, in the preferred embodiment, where the WLAN module is part of the secure element, as the decrypted WLAN access data stays within the secure element. 
         [0023]    The present invention provides, in particular, for the following advantages. It allows a mobile network operator (MNO) to offload data traffic from a congested cellular communications network to selected WLANs. Moreover, the MNO can manage and control WLAN selection in the mobile station. 
         [0024]    These and other features, characteristics, advantages, and objects of the invention will be clear from the following detailed description of preferred embodiments, given as a non-restrictive example, under reference to the attached drawings. The person skilled in the art will appreciate, in particular, that the above preferred embodiments can be combined in several ways, which will result in additional advantageous embodiments that are explicitly supported and covered by the present invention. In particular, the person skilled in the art will appreciate that the above described preferred embodiments can be implemented in the context of the above-mentioned first, second, third and fourth aspect of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  shows a schematic overview of a mobile communications system illustrating different aspects of the present invention; 
           [0026]      FIG. 2  shows a diagram illustrating a method for remotely managing the access of a mobile station to a WLAN according to a preferred embodiment of the invention; and 
           [0027]      FIG. 3  shows a diagram illustrating a method for remotely managing the access of a mobile station to a WLAN according to further preferred embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0028]      FIG. 1  shows schematically the components of a mobile communications system  10  as well as some of the communication channels or links between the components of this system  10  that illustrates several aspects of the present invention. 
         [0029]    An exemplary mobile station  12  is shown in  FIG. 1  that consists of a mobile terminal  14  and a secure element  20  for securely storing and processing data that uniquely identifies the user of the mobile station  12 . According to preferred embodiments of the invention the secure element  20  is configured as a subscriber identity module (SIM), as the SIM currently is the most popular type of secure element used in cellular communications systems for unique and secure subscriber identification as well as for the provision of different special functions and value-added services. The person skilled in the art will appreciate, however, that other types of secure elements that, depending on the underlying generation and type of cellular communications system standard, are designated as UICC, USIM, R-UIM or ISIM, are also encompassed by the present invention. Moreover, the person skilled in the art will appreciate that the present invention can be advantageously put into practice, for instance, by means of a secure element  20  that can be removably inserted into the mobile terminal  14  or, alternatively, a secure element  20  that is embedded into the mobile terminal  14 . 
         [0030]    The mobile station  12  is configured to communicate via the air interface (or radio link) with a cellular communications network in the form of a Public Land Mobile Network (PLMN)  50 , preferably operated by a Mobile Network Operator (MNO) according to the GSM standard. To this end, preferably an International Mobile Security Identity (IMSI) and/or an authentication key Ki are securely stored on the secure element  20  for authenticating the secure element  20  relative to the PLMN  50  and communicating therewith. 
         [0031]    In the following, preferred embodiments of the invention will be described in the context of a cellular communications network according to the standards of the Global System for Mobile communication (GSM), as specified in a number of specifications provided by ETSI. However, the person skilled in the art will appreciate that the present invention may be advantageously applied in connection with other cellular communications systems as well. Such systems include third-generation cellular communications systems (3GPP), such as the Universal Mobile Telecommunications System (UMTS), and next generation or fourth-generation mobile networks (4G), such as Long Term Evolution (LTE), as well as other cellular communications systems, such as CDMA, GPRS (General Packet Radio Service) and CAMEL (Customised Applications for Mobile network Enhanced Logic). 
         [0032]    As is well known to the person skilled in the art, the PLMN  50  configured according to the GSM standard generally comprises a base station subsystem consisting of one or more base transceiver stations that define respective cells of the PLMN  50  and are connected to a base station controller. Generally, the base station controller is one of several base station controllers that communicate with a mobile switching center (MSC). Often, a local database called Visitor Location Register (VLR) for keeping track of the mobile users currently located within the cells covered by a MSC (i.e. the MSC service area) is incorporated in the MSC. The MSC provides essentially the same functionality as a central office switch in a public-switched telephone network and is additionally responsible for call processing, mobility management, and radio resource management. The MSC is further in communication with a home location register (HLR), which is the primary database in the PLMN  50  that stores information about its mobile users for authentication. To this end, the HLR generally is in communication with an authentication center (AUC). 
         [0033]    As is known to the person skilled in the art, the communication means between the above described different components of the PLMN  50  may be proprietary or may use open standards. The protocols may be SS7 or IP-based. SS7 is a global standard for telecommunications defined by the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T). The standard defines the procedures and the protocol by which network elements in the public switched telephone network (PSTN) exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup, routing and control. The SS7 network and protocol are used for e.g. basic call setup, management, wireless services, wireless roaming, and mobile subscriber authentication, i.e. enhanced call features providing for efficient and secure worldwide telecommunications. The physical elements by which the elements are grouped or left separate and the interfaces—whether proprietary or open—are left to the MNO, i.e. the operator of the PLMN  50 . 
         [0034]    As can be taken from the enlarged view of the secure element  20  in  FIG. 1 , the secure element  20  comprises a central processing unit (CPU)  22 . The CPU  22  can comprise or be in communication with a memory (not shown) for storing and retrieving data, such as an International Mobile Security Identity (IMSI) and/or an authentication key Ki for authenticating the secure element  20  relative to the PLMN  50 . Preferably, an application  24  is running on the CPU  22  providing for features that will be described in the context of  FIGS. 2 and 3  in more detail further below. The application  24  could be implemented, for instance, as a Java Applet  24 . 
         [0035]    Preferably, the secure element  20  furthermore comprises a WLAN module  26  in communication with the CPU  22  of the secure element  20 . The WLAN module  26  is configured to establish a communication link between the secure element  20  and an access point (also called base station) of a WLAN, for instance the WLAN  30  established by the first access point  32  or the WLAN  40  established by the second access point  42 . A secure element  20  containing a WLAN module that could be advantageously employed according to the present invention is disclosed in WO 2006/137740. Although not preferred from a security standpoint, it is also conceivable that the WLAN module  26  is not part of the secure element  20 , as shown in  FIG. 1 , but part of the mobile terminal  14 . 
         [0036]    Preferably, the WLANs  30 ,  40  established by the first and second access points  32 ,  42  are IEEE 802.11 WLANs, i.e. WLANs configured according to the standard IEEE 802.11 and/or one or more of its sub-standards, such as IEEE 802.11b, 802.11a, 802.11g, 802.11i, 802.11n, and 802.11ac (such WLANs are also known as WiFi networks). Alternatively, one or both of the WLANs  30 ,  40  could be a wireless LAN operated according to the Bluetooth standard (IEEE 802.15.1) or the WiMAX standard (IEEE 802.16). 
         [0037]    As can be taken from  FIG. 1 , the mobile station  12  can communicate via the PLMN  50  with an administration unit in the form of an administration server  52  providing for a backend system. The administration server  52  stores WLAN access data for allowing the mobile station  12  to access one of the WLANs available to the mobile station  12 , for instance, the WLAN  30  or the WLAN  40 . According to preferred embodiments, the administration server  52  can communicate with the first access point  32  (as indicated by the dashed arrow in  FIG. 1 ) and/or the second access point  42 , preferably via the Internet. The function of the administration server  52  in combination with the other elements of the mobile communications system  10  shown in  FIG. 1  will now be described under further reference to  FIGS. 2 and 3 . 
         [0038]    In step S 1  of  FIG. 2 , preferably, the application  24  running on the CPU  22  of the secure element  20  triggers the search for WLANs available in the vicinity of the mobile station  12 . In response thereto the WLAN module  26 , which preferably is part of the secure element  20 , searches for and compiles information about available WLANs in the vicinity of the mobile station  12 . This searching for available WLANs could be an active probing or a passive scanning for available WLANs. In an active probing process the WLAN module  26  of the mobile station  12  could send a broadcast signal to cause any access points present within the communication range of the mobile station  12  to emit a beacon frame including information about the WLAN established by the respective access point. In a passive scanning process the WLAN module  26  could simply listen for beacon frames being periodically transmitted by any access points of WLANs within the vicinity of the mobile station  12 . For instance, if appropriately located within the respective communication ranges of the first access point  32  and the second access point  42 , the WLAN module  26  could receive beacon frames from both the access point  32  (see step S 2  of  FIG. 2 ) and the access point  42  shown in  FIG. 1 . 
         [0039]    As is known to the person skilled in the art, an access point configured according to the standard IEEE 802.11 and/or one or more of its sub-standards broadcasts regularly, for instance every 100 microseconds, a so-called beacon frame. Part of this beacon frame is a WLAN specific identifier in the form of a SSID (Service Set Identifier). Generally, the beacon frame, furthermore, comprises information about the transmission rates supported by the access point as well as the encryption protocol used by the access point. Preferably, these and possibly other information about a given WLAN are extracted by the secure element  20  and its WLAN module  26  from a beacon frame received from the corresponding access point. 
         [0040]    Once the mobile station  12  has compiled the information about the available WLANs within its vicinity, it can upload this WLAN data to the administrations server  52  (see step S 4  in  FIG. 2 ). Prior to the upload of the WLAN data, i.e. the information about the WLANs available in the vicinity of the mobile station  12 , to the administration server  52 , preferably the administration server  52  has to authenticate the mobile station  12  (see step S 3  of  FIG. 2 ). This authentication could be implemented in the form of the standard GSM challenge-response authentication protocol, which is well known to the person skilled in the art and for this reason will not be described in greater detail herein. 
         [0041]    Having successfully been authenticated, the mobile station  12  is allowed to upload the compiled data about the available WLANs  30 ,  40  to the administration server  52  (see step S 4  of  FIG. 2 ). As already mentioned above in the context of  FIG. 1 , the mobile station  12  and the administration server  52  preferably communicate via the PLMN  50 . Preferably, the communication between the mobile station  12  and the administration server  52  via the PLMN  50  is done by SMS protocol (Short Message Service), USSD protocol (Unstructured Supplementary Service Data) or a similar text message protocol. In the case, where the SMS protocol is used to upload the WLAN data to the administration server  52 , the WLAN data can be addressed to the administration server  52  by using a special phone number associated with the administration server  52  that, preferably, is stored within the secure element  20 . 
         [0042]    Once the administration server  52  has received the data about the available WLANs  30 ,  40  from the mobile station  12  in step S 4  of  FIG. 2 , it will use this WLAN data and, in particular, any WLAN specific identifiers, such as SSIDs, therein to look for corresponding WLAN access data that would allow the mobile station  12  to attach to the corresponding WLAN  30 ,  40  (see step S 5  of  FIG. 2 ). To this end, the administration server  52  preferably maintains an up-to-date database of WLAN access data for a plurality of WLANs that the mobile station  12  might encounter, including any WLANs operated by the MNO. Preferably, this WLAN access data includes for each respective WLAN a WLAN specific identifier, such as the SSID (Service Set Identifier), a user name, a user password and/or any secret keys required for successfully attaching to a respective WLAN. 
         [0043]    In order to be able to resolve any ambiguities with respect to the names of different WLANs, i.e. two or more WLANs having the same SSID, preferably the administration unit  52  is, furthermore, configured to use information about the location of the mobile station  12 , as defined, for instance, by the Location Area Identity (LAI), when retrieving WLAN access data for the WLANs discovered by the mobile station  12 . 
         [0044]    Alternatively, it is conceivable that the administration server  52  tries to obtain WLAN access data, for instance, WLAN access data that is not available in the administration server&#39;s database, from other sources, for instance, directly from an access point, such as the access point  32  (as indicated by the dashed line in  FIG. 1 ) or a server connected therewith. 
         [0045]    In step S 6  of  FIG. 2  the administration server  52  creates a prioritized list of preferred WLANs selected out of the list of available WLANs  30 ,  40 . Of course, this prioritized list of preferred WLANs could contain only a single WLAN. For instance, in the context of  FIG. 1  it is conceivable that the mobile station  12  informs the administration server  52  via the PLMN  50  that the mobile station  12  is within the respective communication ranges of the WLANs  30 ,  40  and that, in response thereto, the administration server  52  provides the mobile station  12  with the WLAN access data for the WLAN  30 , but not for the WLAN  40 , because the WLAN  30  is known to the MNO to be operated by a trusted provider, whereas the WLAN  40  is not. 
         [0046]    Preferably, the administration server  52  is configured to create this prioritized list of WLANs on the basis of selection rules implemented in the administration server  52 . These selection rules could take, for instance, the following factors into account: the maximum data throughput of a WLAN, the current data throughput of a WLAN, the signal strength of the WLAN as measured by the mobile station  12 , whether the WLAN is operated by a party known to the MNO or the MNO itself, and the like. Preferably, the administration server  52  is further configured, when selecting a preferred WLAN or creating a prioritized list of preferred WLANs, to take into account the technical capabilities of the mobile station  12 . Information about the technical capabilities of the mobile station  12  could be transferred by the mobile station  12  to the administration server  52  together with the information about available WLANs (see step S 4  of  FIG. 2 ) or be stored in the administration server  52 . 
         [0047]    In step S 7  of  FIG. 2  this prioritized list together with the corresponding WLAN access data is uploaded to the mobile station  12  via the PLMN  50 . Preferably, this data is stored in the secure element  20  which houses the WLAN module  26  as well. Preferably, the WLAN access data is sent from the administration server  52  over the PLMN  50  to the mobile station  12  in encrypted form and is decrypted within the secure element  20 , as is the case, for instance, according to the GSM standard. This is advantageous particularly in the preferred embodiment, where the WLAN module  26  is part of the secure element  20 , as the decrypted WLAN access data stays within the secure element  20 . 
         [0048]    Once the mobile station  12  has downloaded the prioritized list of preferred WLANs along with the respective WLAN access data from the administration server  52  (see step S 7  of  FIG. 2 ) and stored this data, preferably, in the secure element  20 , the mobile station  12  can use this WLAN access data to connect to try to connect to one of the WLANs  30 ,  40  on the prioritized list of preferred WLANs (see step S 8  of  FIG. 2 ). Preferably, the mobile station  12  is configured to try to connect or attach to the WLANs mentioned on the prioritized list according to the order defined therein. 
         [0049]    According to preferred embodiments of the invention, the application  24 , implemented on the mobile station  12 , preferably on its secure element  20 , is configured to cause the mobile station  12  to perform the steps of the method described above in the context of  FIG. 2 . In particular, the application  24  is configured to trigger the search for available WLANs  30 ,  40  by means of the WLAN module  26  of the mobile station  12 , to communicate information about the discovered WLANs via the PLMN  50  to the administration server  52 , and to access one of the WLANs  30 ,  40  using the WLAN access data downloaded from the administration server  52 . Preferably, the application  24  could trigger the search for available WLANs in response to events, such as the following ones: terminal events, such as power-on, the expiration of a timer, and/or the discovery of a new WLAN. According to a further alternative embodiment, the mobile station  12  could be configured to periodically search for new WLANs within the vicinity of the mobile station  12  and to communication about new WLANs to the administration server  52  once these are discovered. 
         [0050]    Moreover, the application  24  running on the CPU  22  of the secure element  20  can be configured to cause the display of a message on a display of the mobile station  12  informing the user of the mobile station  12  about the preferred WLAN or the prioritized list of WLANs provided by the administration server  52 . The application  24  could be further configured such that the user of the mobile station  12  has to confirm the attachment to the preferred WLAN or one of the WLANs from the prioritized list of WLANs selected by the administration server  52 , before the mobile station  12  can try to attach thereto. 
         [0051]    Alternatively or additionally, the search for new WLANs and/or the transmission of information about new WLANs to the administration server  52  can be triggered by the mobile terminal  14  or the administration server  52 , as shown in step S 1 ′ or step S 1 ″ of  FIG. 3 . For instance, in case the data traffic within the cell of the PLMN  50  the mobile station  12  is located in is higher than a pre-defined threshold, the administration server  52  could cause the mobile station  12  to search for available WLANs  30 ,  40  that might be suitable for offloading data traffic. 
         [0052]    Steps S 2 ′ to S 8 ′ of the two preferred embodiments shown in  FIG. 3  are identical to steps S 2  to S 8  of the preferred embodiment described above in the context of  FIG. 2 . In comparison to the preferred embodiment shown in  FIG. 2  the preferred embodiments shown in  FIG. 3  contain the additional step that, after the mobile station  12  has attached to one of the available WLANs using the prioritized list and the corresponding WLAN access data provided by the administration server  52  (see step S 8 ′ of  FIG. 3 ), the mobile station  12  informs the administration server  52  about which one of the WLANs mentioned on the prioritized list it has successfully attached to. Moreover, the mobile station  12  could be configured to also inform the administration server  52  about any unsuccessful attachment attempts and, if possible, the reason therefore, such as an invalid password. This feedback provided by the mobile station  12  allows the administration server  52  to keep its WLAN access data up-to-date. It is conceivable that this feedback is provided to the administration unit via the PLMN  50  and/or the WLAN the mobile station  12  has successfully attached to. 
         [0053]    The present invention has been described in the context of some advantageous embodiments implemented in the context of a GSM network. However, this is not to be understood to restrict the invention to the details of these embodiments, which are presented for illustrative purposes only, as the general idea of the present invention could equally be implemented in the context of cellular communications systems other than GSM. In other words, in light of the above detailed description the person skilled in the art will appreciate that modifications and/or additions can be made to the methods and devices as described heretofore, which are to be considered to remain within the scope of the present invention as defined by the appended claims.