Abstract:
A method for communicating between a cellular system and a mobile terminal by way of a standard wireless LAN and the Internet allows data communications to traverse the core of the cellular network, thereby allowing monitoring of the time and volume usage by the subscriber for billing purposes. The user terminal has a communication protocol for communicating with the wireless LAN, over which is a EAP/EAPOL protocol. A Radio Adaptation Layer (RAL) protocol overlies the EAP/EAPOL protocol. At the cellular system, a Serving GPRS Support Node has a RAL/EAP/TCP-IP protocol for providing communications between the wireless LAN and the cellular system by way of the Internet.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to communications between a user terminal and a cellular communication system by means of a wireless LAN. The wireless LAN communicates with the cellular system by means of the Internet. The user terminal is attached to the cellular communication system through the wireless LAN access point.  
       BACKGROUND OF THE INVENTION  
       [0002]     Public Wireless Local Area Networks (WLAN) systems are becoming more common, but the WLAN systems are for the most part independently operated and controlled. Thus, there are many separate owner/operators of WLAN systems. Each separately controlled system is termed a “domain.” Because of the large number of owner/operators or domains, it is difficult or impossible for a user to subscribe to all the different WLAN systems to which connection may be made, especially in view of the fact that the potential user may become aware of the existence of a wireless local area system in a particular area only when his portable communication device announces its availability. In order to ameliorate this situation and to provide improved service, some service providers aggregate, in some way, two or more separate WLAN systems by entering into agreements with other providers.  
         [0003]     A communications service provider may provide various different kinds of service. In those cases in which the communications service provider is a cellular communications network (3GGP or cellphone service) provider, the provider may make available Internet access, with the user authenticated by the cellular network but Internet access by way of the Wireless Local Area Network (WLAN). In such Internet-only WLAN service, the Internet data never traverses or moves over the cellular system. However, the authentication, authorization, and accounting control data relating to the Internet service may traverse the cellular system. The term “loose coupling” is applied to communications in which control data for establishing a connection, and authenticating, authorizing, and accounting information of the user is routed through the WLAN to the cellular system, but once the connection is set up, the user data is routed to the internet, or other network, through only the WLAN. The loose coupling arrangement has the disadvantage that the cellular and WLAN systems are substantially independent, and the cellular system operator therefore does not have any ready access to information about the time usage of the WLAN system, or the volume of data, either or both of which may be useful in customer billing. Moreover the user cannot access certain cellular network specific services like SMS.  
         [0004]     Another possible type of communication service is full cellular network based access, in which the user data and the control information both traverse the cellular network. In such service, the WLAN acts as a radio network portion of the cellular network and the user has access to the full cellular network service set, including Internet access and specific services like SMS. This type of communication is known as “tight” coupling. While theoretically appealing and potentially advantageous to the user and service provider, tight coupling has been considered by the various standardization groups to be too complex, as the protocols and requisite infrastructure would adversely affect the WLAN. Currently, certain standards bodies, such as the European Telecommunication Standard Institute (ETSI), Institute of Electrical and Electronic Engineers (IEEE), and 3 rd  Generation Partnership Project (3GPP) are focusing on the loose coupling model due to its relative simplicity.  
         [0005]      FIG. 1  is a simplified block diagram of a prior art GPRS 3GPP digital cellular telecommunications system designated generally as  10 . In general, such a system adheres to standards for digital cellular telecommunication system (Phase 2+) (GSM); Universal Mobile Telecommunications System (UMTS); General Packet Radio Service (GRPS); Service description; Stage 2 (3GPP TS 23.060 version 3.7.0 Release 1999. The system  10  of  FIG. 1  includes a radio access network (RN or RAN)  12  and a core network (CN)  14 . The radio access network  12  includes a set  16  of Radio Network Controllers (RNC), some of which are illustrated as  16   a  and  16   b . Each radio network controller (RNC) of set  16 , such as RNC  16   b , controls at least one “base station” or “Node B.” In  FIG. 1 , RNC  16   b  controls a set  18  including node B base stations  18   a  and  18   b . Each node B base station corresponds to a cell of the cellular system. Each node B base station or cell communicates by wireless (radio) means with one or more mobile users (UE), one of which is designated  20 , located in the zone of the corresponding cell, as suggested by symbol  22 .  
         [0006]     The core network (CN)  14  of the telecommunications system  10  of  FIG. 1  includes a set  30  of Serving GPRS Support Nodes (SGSN), two of which are designated  30   a  and  30   b . Each SGSN of set  30  provides services for managing the connection between the core network  14  and the user  20 , by way of the radio access network  12 . In this context, management of the connection refers to management of connection, authentication, and mobility. In this context, connection management relies on the process to provision network resources such as radio resources, memory, and priority in order to be able to transmit data. Mobility is the set of protocols/processes which allow the user to move among several cells, and is also known as handover. Each SGSN also serves as a “front end,” providing the user  20  with access to other 3G services such as Short Messaging System (SMS).  
         [0007]     The Serving GPRS Support Nodes (SGSN) of set  30  of SGSNs of core network  14  communicate with a Home Location Register (HLR) which is illustrated as an external memory  40 . The HLR  40  is the database that includes all relevant information relating to each subscriber to the network  10 . The SGSN of set  30 , as for example SGSN  30   a , identifies and authenticates a user by reference to the HLR  40 .  
         [0008]     The Gateway GPRS Support Node (GGSN)  32  of core network  14  provides interconnection between core network  14  and an external Internet-Protocol (IP) based Packet Data Network (PDN)  110 , such as the Internet.  
         [0009]     The system  10  also includes a Border Gateway (BG)  34  in core network  14 . Border gateway  34  is a function, which allows the user to roam between or among GPRS networks belonging to different domains (operators). Border Gateway  34  is connected to an external Public Land Mobile Network (PLMN)  134 .  
         [0010]     In operation of system  10 , the RNCs  16   a ,  16   b  of set  16  implement or realize the interface between the core network  14  and the radio access network  12 .  
         [0011]      FIG. 2   a  is a simplified illustration of the control protocol stacks of the mobile terminal (UE)  20 , the node B of set  18 , the Radio Network Controllers (RNC) of set  16 , and the Serving GPRS Support Nodes (SGSN) of set  30 , and  FIG. 2   b  illustrates a sequence of the successive protocol operations for opening a user data channel between the UE  20  and SGSN  30  of  FIG. 2   a . In  FIG. 2   a , protocols associated with the mobile terminal UE are designated generally as  220 , protocols associated with the Node B are designated generally as  250 , protocols associated with the RNC are designated generally as  216 , and those associated with SGSNs are designated generally as  230 . The radio interface between the mobile node UE and the Node B corresponds to one of the standardized 3G cellular radio interface, such as WCDMA. In the mobile terminal UE, the MAC (Medium Access Control) protocol in conjunction with the RLC (Radio Link Control) protocol allows the transport of information, whatever its nature (i.e. user data or control). The RRC (Radio Resource Control) protocol is used between the UE and the RNC for radio connection control (creation, removal, and/or modification of the connection). The GMM (GPRS Mobility Management) protocol and CM (Connection Management) protocols are used between the mobile terminal and the SGSN for respectively mobility management (authentication and handover) and user data connection management. The Node B (or base station) is under the control of an RNC through the usage of a set of protocols, which are not represented in  FIG. 2   a . The RNC is controlled by the SGSN by means of the RANAP (Radio Network Application Protocol) protocol that is carried by a protocol stack based on ATM (Asynchronous Transfer Mode) not depicted. The SGSN communicates with the GGSN  32  of  FIG. 1  for control purposes by means of the GTP-C (GPRS Tunneling Protocol-Control) that is carried by a protocol stack based on the TCP/IP protocol stack.  FIG. 2   b  represents a sequence diagram of the successive protocol operations in order to open a data user channel between the mobile terminal and the SGSN.  
         [0012]     Initially, a mobile terminal UE such as terminal  20 , once switched on, catches or captures broadcast downlink information, thereby allowing the UE to send an attachment request to the SGSN through a physical transmission opportunity. The SGSN immediately opens a signaling channel used only for control purposes. This process is depicted in  FIG. 2B  and is represented as a first step by a numeral  1  within a circle. Once the basic signaling (or control) channel is set up, the mobile terminal UE requests a user data connection characterized by means of QOS (Quality Of Service) parameters through or by means of a Connection Management (CM) protocol (step  2  in  FIG. 2B ). The appropriate SGSN, such as SGSN  30   a  of  FIG. 1 , verifies the request (determines if the mobile terminal is authorized for the requested service) and requests through or by means of the Radio Access Network Protocol (RANAP) that an associated RNC, which in this case could be RNC  16   b , establish the radio connection associated with the QOS parameters (circled step “ 3 ” in  FIG. 2   b ). The RNC ( 16   b  in this case) translates the QOS parameters into parameters which are used to establish the corresponding radio connection, and commands such a radio connection in both the base station (Node B  18   a  in this case) and the mobile terminal UE, corresponding to circled step  4  in  FIG. 2   b ). The RNC controls the terminal by means of the Radio Resource Control (RRC) protocol. The UE  20  and the Node B  18   a  use the parameters transmitted by the RNC (carry them without change) to configure their respective radio protocol layers, including Radio Link Control (RLC), Medium Access Control (MAC), and physical layers. The radio channel is then established (circled step  5  in  FIG. 2   b ). Both the Node B  18   a  and the mobile terminal UE confirm the operation, and the RNC acknowledges the operation to the SGSN (circled step  6  in  FIG. 2   b ). Last, the SGSN acknowledge the success of the operation to the mobile terminal using the CM protocol (circled step  7  in  FIG. 2   b ).  
         [0013]      FIG. 3  is a simplified representation of 3G GPRS user data protocol stack. User data (not illustrated) originating at the user terminal UE, which may, for example, be in Internet-Protocol (IP) form, is transported between the user terminal UE and the SGSN using the Packet Data Compression Protocol (PDCP), which compresses the IP header in order to conserve some bandwidth. Between the RNC stack and the SGSN stack  330 , and within the remainder of the core network  14  of  FIG. 1  up to the stack (not illustrated in  FIG. 3 ) of the GGSN of  FIG. 1 , the user data is carried by GPRS Tunnel Protocol (GTP) that is implemented over UDP/IP represented in  FIG. 3 .  
         [0014]      FIG. 4  is a conceptual representation of the 3G-WLAN loose coupling arrangement. In  FIG. 4 , the Internet is illustrated as a cloud or circle  410 , the public WLAN system as a cloud or circle  412 , and the 3G core network, corresponding to  14  of  FIG. 1 , is designated  414 . Additionally,  FIG. 4  shows a representative web server  416  and a mobile user  420 , corresponds to user  20  of  FIG. 1 . In the prior-art scenario represented by  FIG. 4 , user  420  is within the coverage region of public WLAN  412 .  
         [0015]     When the mobile user  420  of  FIG. 4  turns ON or energizes his mobile terminal so as to make a connection request illustrated as  430 , the WLAN  412  detects this fact, and directs or redirects the connection request by way of a control path  428  through the Internet  410  toward an Authentication, Authorization, and Accounting (AAA) portion  424  of the core network  414 . AAA  424  consults its Home Location Register  40  to determine if the user&#39;s data corresponds with that of an authorized user. After being authenticated, the AAA  424  authorizes the WLAN  412 , to let the user data traffic through the access point. The user is then able to use the Internet, as by browsing, by way of a data path  426  communicating with web server  416 .  
         [0016]     In the communication domain, the protocols are split among three different planes, namely Management, Control and User. The Management protocols provide a way to configure the equipments. The Control protocols provide a way to control/command dynamically the equipments (e.g. connection establishment). The user plane protocols provide a way to carry user data. The three protocol stacks may include common protocols especially those relative to the transport of information.  FIG. 5  shows the Control plane protocol stack in case of the loose coupling model. The corresponding User plane protocol stack based on TCP/IP/Ethernet corresponds with the prior art and is not represented, but is simply IP over Ethernet over the WLAN MAC (IEEE 802.11 in our example).  
         [0017]     The control protocol stacks associated with the mobile terminal  420 , the Access Point (AP)  412 , and the AAA server  424  of  FIG. 4  are represented in  FIG. 5  as  520 ,  516 , and  530 , respectively.  FIG. 5  assumes IEEE 802.11 as the radio interface between the mobile terminal  520  and the AP  516 , but it can be also other WLAN protocols, such as the ETSI Hiperlan2 protocol. As illustrated in  FIG. 5 , EAPOL information is transmitted between the mobile terminal  520  and the access point  516 . EAPOL refers to EAP Over LAN, where the LAN is the public WLAN. EAPOL is a standardized (IEEE 802.1X) protocol that is used to carry EAP packets within Ethernet frames. “EAP” stands for Extended Authentication Protocol, which is a protocol that can be used to carry any kind of authentication protocol. The authentication protocol may be, for instance, the EAP AKA and EAP SIM that might be chosen by the 3GFP standard body. The DIAMETER protocol is a well-known IETF protocol (RFC 3588) used to control the authorization of the user by the AAA. It could be replaced by other equivalent protocols, such as the RADIUS protocol (RFC 2138). Once the user  520  is authenticated, meaning that the AAA server  424  of  FIG. 4  retrieved a corresponding entry in its Home Location Register or subscription database  40  and the authentication protocol succeeded, the AAA server  424  ( 530  of  FIG. 5 ) sends a DIAMETER message to the AP  412  ( 516  of  FIG. 5 ) in order to unblock the Ethernet traffic corresponding to the authenticated user  420  ( 520  of  FIG. 5 ).  
       SUMMARY OF THE INVENTION  
       [0018]     The invention provides a method for implementing a tight coupling arrangement for allowing a mobile terminal to communicate with a communications network through first and second networks, wherein the first network comprises a wireless local area network (WLAN) and the second network comprises a cellular network. The invention places certain radio network control protocols within the mobile terminal to advantageously allow a tight coupling arrangement to be implemented using a WLAN access point that has been configured for a loose-coupling arrangement. Specifically, the invention provides a method for implementing a tight coupling arrangement between first and second communications networks for allowing a mobile terminal to communicate with a third communications network through the first and second communications networks, comprising the steps of: (a) providing, in the first communications network, an access point having protocol stacks adapted for operation within a loose coupling arrangement that allows the mobile terminal to communicate with the third communications network through the first communications network without traversing through the second communications network; (b) providing, in the mobile terminal, radio network controller protocol stacks that directly interface with corresponding radio network controller protocol stacks in an access device of the second communications network; and (c) providing, in the access device of the second communications network, the corresponding radio network controller protocol stacks for interfacing with the mobile terminal radio network controller protocol stacks, whereby the mobile terminal communicates directly with the access device to traverse the second communications network to thereby communicate with the third communications network in a tight coupling arrangement.  
         [0019]     In a particular mode of this aspect of the method of the invention, the step of communicating particular data includes the further step of communicating the particular data between the Serving GPRS Support Node and a server associated with the Internet. As a result, the user terminal can access or browse the Internet.  
         [0020]     According to another aspect of the invention, a method for communicating between a mobile user terminal and a cellular network by way of a wireless LAN comprises the steps of providing at the user terminal a communication protocol for communicating with the wireless LAN, and providing at the user terminal, and over the communication protocol, a standardized EAPOL protocol for packet frame communication. In addition, the method includes the provision, at the user terminal, and over the EAPOL protocol, of a standardized EAP protocol for communicating authorization control information, and further providing, at the user terminal, and over the EAP protocol, a Radio Adaptation Layer protocol, which Radio Adaptation Layer protocol provides control of the radio communications. At the cellular network, a Serving GPRS Support Node is provided. An Internet protocol stack suited for communication over the Internet is associated with the Serving GPRS Support Node. A standardized EAP protocol for communicating authorization control information over the Internet is provided over the Internet protocol stack. A Radio Adaptation Layer protocol, which Radio Adaptation Layer protocol provides control of the radio communications, is provided over the EAP protocol at the Serving GPRS Support Node. Communications are between the wireless LAN and the cellular system by way of the Internet. Finally, communications are provided between the user terminal and the wireless LAN by use of the Radio Adaptation Layer.  
         [0021]     In a particular mode of this other method, the step of providing, at the cellular network, a Serving GPRS Support Node, and associating with the Serving GPRS Support Node an Internet protocol stack suited for communication over the Internet, includes the step of providing at least TCP/IP protocol over a physical layer, and providing Diameter protocol over the TCP/IP protocol. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0022]      FIG. 1  is a simplified functional block diagram or architecture of a prior art 3G GPRS digital cellular telecommunications system;  
         [0023]      FIG. 2   a  is a simplified representation of 3G GPRS protocol stacks of various portions of the system of  FIG. 1 , and  FIG. 2   b  illustrates a sequence of the successive protocol operations for opening a user data channel between the various portions of  FIG. 1 ;  
         [0024]      FIG. 3  is a simplified representation of 3G GPRS user data protocol stack;  
         [0025]      FIG. 4   FIG. 4  is a conceptual representation of prior-art 3G-WLAN loose coupling;  
         [0026]      FIG. 5  represents the control protocol stacks associated with the mobile terminal, the Access Point (AP), and the AAA server of  FIG. 4 ;  
         [0027]      FIG. 6  is a simplified representation of the flow of control information and data according to an aspect of the invention; and  
         [0028]      FIGS. 7 and 8  illustrate the control and data protocol stacks according to an embodiment of the invention, for enabling the connectivity functions expressed in  FIG. 6 .  
     
    
     DESCRIPTION OF THE INVENTION  
       [0029]     The prior art presented above shows that for WLAN-cellular network inter-connection, the loose coupling model is simple, but the relative simplicity is associated with some undesirable limitations or problems. These include the fact that the authentication protocol is new (IEEE 802.1x, EAP, . . . ) and consequently requires a new equipment (AAA server  424  in  FIG. 4 ) inside the cellular network, and new interfaces with legacy equipments (HLR  40  in  FIG. 4 ), all compliant with the new paradigm. In addition, a mobile terminal equipment like a cellular phone must include two different protocol stacks, depending upon whether the attachment is done through the conventional cellular radio interface ( 22  in  FIG. 1 ) or through the WLAN radio interface ( FIG. 7 ). Further, the Loose coupling model prevents the access of cellular network specific services like SMS (Shot Messaging System).  
         [0030]     The invention implements a tight coupling model in which, as in the loose coupling model, the mobile terminal UE is attached or communicates through a WLAN as an access point. In the exemplary embodiment, the WLAN communicates with the cellular network through the Internet, however, it is to be understood that the WLAN may also communicate with the cellular network through other suitable communication networks. The protocol stack in a WLAN used in a system according to an aspect of the invention has a protocol stack which is (or at least can be) identical to that used in the case of loose coupling, and therefore a WLAN which is (or can be) used for the loose coupling model can also handle tight coupling traffic without any modification. A further advantage which can be achieved in the invention, but which is not found in the prior art loose coupling model, is that the signaling protocols in the user terminal and the SGSN, which are used to manage user data connections and to manage mobility (including authorization), are those already standardized by cellular network specifications such as the CM (Connection Management) and the GMM (GPRS Mobility Management) protocol. According to a further aspect of the invention, in order to avoid the complexity of the radio control protocols (RRC in  FIG. 2   a ) linked with the cellular network radio interface ( 22  in  FIG. 1 ) technology and its complete redesign, a new simplified protocol called RAL (Radio Adaptation Layer) is defined. The RAL layer is a subset of the known RANAP protocol and includes the commands for establishing and managing, i.e., setting up, a connection. This new protocol is very similar to the RANAP ( FIG. 2   a ) protocol, and thus is readily implemented. The RAL protocol layer is also similarly implemented in the SGSN. According to one aspect of the invention, and in contradistinction to the loose coupling scenario set forth in conjunction with  FIGS. 1, 2   a ,  2   b ,  3 ,  4 , and  5 , connection requests from the SGSN to the mobile terminal UE by means of this RAL protocol directly provide QOS parameters to the mobile terminal, and the mobile terminal translates these parameters into radio dependent parameters. Also, as described below in conjunction with  FIG. 8 , the transport of user data is compliant with the conventional model, described above in conjunction with  FIG. 3 , in which the transport protocol GTP-U is used between the SGSN and the mobile terminal UE, thereby implying no change in the SGSN.  
         [0031]      FIG. 6  is a simplified representation of the flow of control information and data according to an aspect of the invention. In  FIG. 6 , elements corresponding to those of  FIG. 4  are designated by like reference alphanumerics. As illustrated in  FIG. 6 , the control information, including the request for access by the mobile terminal  620 , flows between the mobile terminal  620  and the core network  630  of a cellular communications system  600  by means of a control path  628 , which passes through the public WLAN  412  and the Internet  410 . User Data flowing between mobile terminal  620  and a remote web server illustrated as  416  flows by a data path  626   a  through the WLAN  412 , Internet  410 , and core network  630 , and then by a further path  626   b  between core network  630  and web server  416 , again by way of Internet  410 .  
         [0032]      FIGS. 7 and 8  illustrate the control and data protocol stacks, respectively, according to an embodiment of the invention, for enabling the connectivity functions expressed in  FIG. 6 . In  FIG. 7, 720  designates the control protocol stack for the mobile user UE ( 620  of  FIG. 6 ),  730  the control protocol stack for the SGSN ( 630  of  FIG. 6 ), and  760  the control stack for the access point (AP). The protocol stack of access point AP of  FIG. 7  is exactly the same as that of a prior-art wireless LAN used in the loose coupling model. Comparison of the stacks of  FIG. 7  with those of the loose coupling solution, as illustrated in  FIG. 2   a , shows that all the protocols related to the radio link, namely stacks  250  and  252 , have disappeared. The 3GPP UMTS Radio Access Network Adaptation Protocol (RANAP) used in the arrangement of  FIG. 2   a  is replaced in  FIG. 7  by Radio Adaptation Layer Protocol (RALP), which is a subset of RANAP and implemented in the mobile terminal and SGSN, plus some extra commands related to encryption.  
         [0033]     Most of the RALP messages are based on RANALP. Therefore, the RALP header contains a value that indicates the format of the message. The general RALP message format includes (a) version number, (b) integrity check information (only when integrity protection is required), and (c) remaining information elements (IE).  
         [0034]     Thus, the Radio Adaptation Layer (RAL) entity of UE  720  and SGSN  730  performs the functions of the RANAP. The RALP control information is transmitted between user terminal UE  720  of  FIG. 7  and SGSN  730  of  FIG. 7  by way of access point (AP)  760 , but the RALP control information is not processed by the access point, so essentially flows directly between the UE and the SGSN, as suggested by path  761 .  
         [0035]     In  FIG. 7 , note that the access point (AP)  760  is configured, or has protocol stacks, exactly as set forth in conjunction with the “loose coupling” solution of  FIG. 5 . More particularly, the access point (AP)  516  of  FIG. 5  communicates with the mobile terminal with physical radio equipment and the EAPOL/WLAN protocol, corresponding to the left portion of AP stack  760  of  FIG. 7 . Similarly, access point  516  of  FIG. 5  communicates with the Authentication, Authorization, and Accounting (AAA) portion  530  of the core network  414  of  FIG. 4  by means of a physical level (not expressly illustrated) together with Diameter/TCP-IP protocols, which is identical to the protocol stack represented on the right side of the AP stack  760  of  FIG. 7 . Also note that the authentication protocol and the other control protocols set forth in  FIG. 7  are those already specified by the 3G cellular specification document, and more particularly by the 3GPP UMTS: connection management SM and SMS specifications and GMM as introduced in the first section of that document. Consequently, a wireless LAN access point can operate in the inventive arrangement without any substantive modification necessary for implementing a tight coupling arrangement, which is a major advantage.  
         [0036]     When a mobile terminal UE moves into the coverage area of a wireless LAN, or is initially switched ON in such a coverage area, it first establishes an EAP connection with a remote server (SGSN in this case) in conformance with the procedure discussed in relation to the loose coupling scenarios. The access point authorizes or carries only the control or EAP traffic. When the UE is authenticated according to the relevant protocol, such as 3G GPRS protocol (GMM), the SGSN  730  authorizes the user&#39;s traffic by sending a DIAMETER message, known in the art, to the access point (AP)  760 , using the procedure followed by the AAA server  424  in the loose coupling scenario.  
         [0037]     When the user terminal UE  720  requests connection by means of the connection management (CM) protocol, the SGSN  730  processes the request and, using the RALP protocol, requests that the mobile unit establish the radio part of the connection, by which data can be communicated. In response to the request, the user terminal UE  720  translates the request into parameters which are used to establish the corresponding radio connection, ultimately completed by way of the WLAN protocol.  
         [0038]      FIG. 8  illustrates the data protocol stacks for the user plane for implementing the tight coupling arrangement according to the present invention. Comparing the stacks of  FIG. 9  with the 3G GPRS stacks of  FIG. 3 , it can be seen that all the protocols relating to the GPRS radio network are absent. The illustrated data stacks for the user terminal, the access point, and the SGSN are designated  820 ,  860 , and  830 , respectively. A notable feature of the present invention is that the radio control functions of the RNC are embedded in the control stack of the mobile terminal by virtue of the abovedescribed protocol structure.  
         [0039]     In the data stack arrangement of  FIG. 8 , the GPRS Tunneling Protocol (GTP) is “directly” connected between the user terminal UE  820  and the SGSN  830  as indicated by line  865 . The GTP protocol is carried over UDP/IP as specified by the 3GPP standard. GTP encapsulates user data packets, such as, for example, IP datagrams. The user data packets are carried transparently by the access point AP  860 , and by the SGSN up to GGSN ( FIG. 1 ) that performs the function of an IP router.  
         [0040]     The “tight” communication system according to the invention provides mobility for the user terminal, which is inherent in the GMM protocol. It is also inherently capable of full 3G GPRS service, full accounting, and security, all inherent in the GMM protocol.  
         [0041]     Among the advantages of various embodiments of the invention are that the coupling is realized or accomplished through an Internet Protocol (IP) based network, which may be the Internet, and that the solution is compatible, at least as to the WLAN, with the loose coupling solution as currently envisaged by 3GPP SA2, IEEE 802.11i or ETSI/BRAN.  
         [0042]     Thus, a method according to an aspect of the invention is for communicating data between a mobile terminal ( 620 ) and a server ( 630 ;  416 ). The method comprises the steps of communicating from the mobile terminal ( 620 ) to a wireless LAN access point ( 412 ) a request for data channel access to the Internet ( 410 ), and routing the request ( 628 ) for a data channel from the wireless LAN access point ( 412 ), by way of the Internet ( 410 ), to a Serving GPRS support Node ( 630 ) of a cellular communication system ( 600 ). The method also includes the step of communicating authorization ( 628 ) for the data channel from the Serving GPRS Support Node ( 630 ) of the cellular communications system ( 600 ) to the wireless LAN access point ( 412 ) by way of the Internet ( 410 ). In response to the authorization, a data channel is opened ( 627 ,  626   a ) between the user terminal ( 620 ) and the Serving GPRS Support Node ( 630 ) by way of the wireless LAN ( 412 ) and the Internet ( 410 ). Particular data is communicated between the user terminal ( 620 ) and the Serving GPRS Support Node ( 630 ) of the cellular communication system by way of the data channel wireless LAN access point ( 412 ) and the Internet ( 410 ).  
         [0043]     In a particular mode of this aspect of the method of the invention, the step of communicating particular data includes the further step of communicating the particular data between the Serving GPRS Support Node ( 630 ) and a server ( 416 ) associated with the Internet. As a results the user terminal can access or browse the Internet.  
         [0044]     According to another aspect of the invention, a method for communicating between a mobile user terminal ( 620 ) and a cellular network ( 600 ) by way of a wireless LAN ( 412 ) comprises the steps of providing at the user terminal ( 620 ) a communication protocol (WLANMAC) and Radio) for communicating with the wireless LAN ( 412 ), and providing at the user terminal ( 620 ), and over the communication protocol (WLANMAC and Radio), a standardized EAPOL protocol for packet frame communication. In addition, the method includes the provision, at the user terminal, and over the EAPOL protocol, of a standardized EAP protocol for communicating authorization control information, and further providing, at the user terminal, and over the EAP protocol, a Radio Adaptation Layer protocol, which Radio Adaptation Layer protocol provides control of the radio communications. At the cellular network ( 600 ), a Serving GPRS Support Node ( 630 ) is provided. An Internet protocol stack ( 730 , TCP/IP) suited for communication over the Internet ( 410 ) is associated with the Serving GPRS Support Node ( 630 ). A standardized EAP protocol for communicating authorization control information over the Internet ( 410 ) is provided over the Internet protocol stack ( 730 , TCP/IP). A Radio Adaptation Layer protocol (RAL), which Radio Adaptation Layer protocol provides control of the radio communications, is provided over the EAP protocol at the Serving GPRS Support Node ( 630 ). Communications are between the wireless LAN ( 412 ) and the cellular system ( 600 ) by way of the Internet ( 410 ). Finally, communications are provided between the user terminal ( 620 ) and the wireless LAN ( 412 ) by use of the Radio Adaptation Layer (RAL).  
         [0045]     In a particular mode of this other method, the step of providing, at the cellular network ( 600 ), a Serving GPRS Support Node ( 630 ), and associating with the Serving GPRS Support Node ( 630 ) an Internet protocol stack (Diameter, TCP/IP) suited for communication over the Internet ( 410 ), includes the step of providing at least TCP/IP protocol over a physical layer, and providing Diameter protocol over the TCP/IP protocol.