Abstract:
Interworking of a wireless telephony network ( 12 ) with a wireless Local Area Network ( 10 ) serving at least one mobile terminal user ( 14 ) is accomplished by reserving a General Packet Radio Service (GPRS) communications channel ( 20 ) of the wireless telephony network. Control communications signals received in the WLAN ( 10 ) from the mobile terminal user are communicated across the GPRS channel ( 20 ) to the wireless telephone network ( 12 ) and likewise, control communications signals from the wireless telephony network pass to the WLAN over the channel. Using the GPRS channel to carry control communications signals between the WLAN ( 10 ) and the WLAN ( 12 ) affords the advantage of a loose coupling without the risk of sending sensitive control information over a non-secure link.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to a technique for interworking a wireless Local Area Network (WLAN) with a wireless telephony network to enable sharing of control paradigms, such as those associated with Authentication, Authorization and Accounting.  
         BACKGROUND ART  
         [0002]    Advances in the field of WLAN technology has led to the availability of relatively inexpensive WLAN equipment, which, in turn, has resulted in the availability of publicly accessible WLANs at rest stops, cafes, libraries and similar public facilities. Presently, WLANs offer users the opportunity to access either a private data network, such as a Corporate Intranet, or a public data network such as the Internet. Few if any publicly accessible WLANs offer any type of telephone service, let alone, wireless telephony service.  
           [0003]    Presently, those desirous of obtaining wireless telephony service typically subscribe to one of the many providers of such service. Today&#39;s wireless telephony service providers not only offer voice-calling capability, but also offer General Packet Radio Service (GPRS), thereby affording subscribers the capability of exchanging data packets via a mobile terminal. While GPRS exists in many areas, data transmission rates typically do not exceed 56 Kbs and the costs incurred by wireless network service providers to support this service remain high, making GPRS expensive.  
           [0004]    The relatively low cost to implement and operate a WLAN, as well as the available high bandwidth (usually in excess of 10 Megabits/second) makes the WLAN an ideal access mechanism through which a mobile wireless terminal user can exchange packets with a wireless telephony network. Unfortunately, present-day techniques for interworking (i.e., coupling) WLANs and wireless telephony networks incur difficulties. For example, an interworking technique, known as “loose coupling,” proposes the use of an IP link through the Internet to carry control information between the WLAN and the wireless telephony network. This solution incurs the disadvantage that sensitive validation (authentication) information remains vulnerable to potential interception upon transmission through the Internet.  
           [0005]    To avoid the risk of potential interception of sensitive data, another interworking solution, known as “tight coupling,” proposes to use of a leased private communication line to carry both data and control information between a gateway in the WLAN (typically referred to as an Interworking Unit or IWU) and the wireless telephony network. Employing a leased private line virtually eliminates the possibility of interception at the expense of a monthly line rental that greatly increases operating costs.  
           [0006]    Further, such tight coupling incurs the disadvantage that the IWU in the WLAN has to mimic the wireless network protocol (e.g., the 3GPP protocol for wireless telephony networks that have adopted the 3GPP standard). Under such circumstances, the IWU must mimic the 3GPP protocol in order to appear as a component of the 3GPP wireless telephony network; therefore giving rise to much complexity that is undesirable. For that reason, loose coupling is preferred.  
           [0007]    Thus, there is need for technique for interworking a wireless telephony network and a WLAN that overcomes these disadvantages.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    Briefly, in accordance with the present principles, a method is provided for interworking a WLAN and a wireless telephony network that provides for more secure exchange of authentication information but without the associated cost of a leased line. To provide for such interworking, a wireless telephony channel is established between the wireless telephony network and the WLAN. In practice, one of the wireless channels ordinarily available for communication with a mobile terminal is reserved for communicating information, and particularly control information between the WLAN and the wireless telephony network. To the extent that the WLAN serves multiple mobile terminal users, the signals from such mobile terminal users are multiplexed to yield a communication stream transmitted across the wireless channel to the wireless telephony network.  
           [0009]    Using one of the wireless telephony network communications channels to carry control information, and more particularly, authentication information, between the WLAN and the wireless telephony network affords increased security, as compared to sending such information over the Internet while avoiding the expense of a leased line. Typically, wireless telephony networks embody a security protocol associated with communication of authentication information across the radio channels directly between a mobile terminal user and the wireless telephony network. In the course of gaining direct access to a wireless telephony network, a mobile terminal user must exchange sensitive authentication data with the wireless telephony network. Thus, using an existing GPRS radio channel to carry control information between the WLAN and the wireless telephony network enables the use of interfaces and authentication protocols that already exist in the wireless telephony network. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 depicts a block schematic diagram of a WLAN interworked with a wireless telephony network in accordance with the present principles;  
         [0011]    [0011]FIG. 2 depicts the protocol stacks of the network elements in the WLAN and wireless telephony network of FIG. 1 associated with the use the Authentication, Authorization and Accounting (AAA) protocol;  
         [0012]    [0012]FIG. 3 depicts the protocol stacks of the network elements in the WLAN and wireless telephony network of FIG. 1 associated with the use of the RADIUS protocol; and  
         [0013]    [0013]FIG. 4 depicts the protocol stacks of the network elements in the WLAN and wireless telephony network of FIG. 1 associated with the use of the GMM-like protocol. 
     
    
     DETAILED DESCRIPTION  
       [0014]    [0014]FIG. 1 depicts the combination of a Wireless Local Area Network (WLAN)  10  interworked with a wireless telephony network  12  in accordance with present principles. As discussed in greater detail below, the interworking of the WLAN  10  with the wireless telephony network  12  allows a user, represented by mobile terminal (MT)  14 , to gain access to the mobile telephony network to receive General Packet Radio Service (GPRS) through the WLAN  10 . In its simplest form, the WLAN  10  includes at least one access point (AP)  16  embodied within which is a radio frequency (RF) transceiver (not shown) for exchanging information with a RF transceiver (not shown) in the MT  14 . In practice, the RF transceivers in the MT  14  and AP  16  utilize a well-known wireless communications protocol such as the “Bluetooth” or IEEE 802.11 protocol. In this way, the MT  14 , once in radio communication range with the AP  16  in the WLAN  10 , can easily commence a communications session with the AP  16  without concern about the details of the protocol wireless communications protocol. In practice, the AP  16  has a data connection to a data network  17  illustratively illustrated as the Internet, for communicating data between the MT  14  and the wireless telephony network  10 .  
         [0015]    Within the WLAN  10 , an interworking unit (IWU)  18  establishes a linkage with the mobile telephony network  12  to permit the MT  14  to send control information to, and receive control information from the telephony network to enable the MT  14  to gain access thereto. Such control information will include authentication information. In accordance with present principles, the IWU  18  establishes a linkage with the wireless telephony network  12  by reserving a GPRS radio channel  20  of the kind otherwise used by mobile terminal users (not shown) to communicate directly with the wireless telephony network through a Node  21  served by a radio network controller (RNC)  22 .  
         [0016]    Although illustrated in FIG. 1 as a stand-alone device, the IWU  18  can exist as part of the AP  16 . To accommodate the possibility that the WLAN  10  could have multiple mobile terminals in communication therewith at the same time, the IWU  18  includes a multiplexer (not shown) for multiplexing communications signals from each of the MTs, such as MT  14 , into a combined communications stream for transmission to the wireless telephony network  12 . By the same token, the IWU  18  also includes a de-multiplexer (not shown) for de-multiplexing a combined signal stream received from the wireless telephony network  12  into constituent signals for distribution to corresponding MTs in communication with the WLAN  10 . The multiplexing of signals from several MTs could be realized through the usage of a transport protocol, such as by allocating a User Datagram Protocol (UDP) (not shown) in the wireless telephony network  12 , or could be achieved simply by using an authentication protocol, such as the well-known Authentication, Authorization and Accounting (AAA) protocol discussed hereinafter.  
         [0017]    In practice, the wireless telephony network  12  conforms to one of the 2.5 G or 3G Standards for Mobile Wireless Telephony Networks as known to those skilled in the art. In accordance with such standards, the wireless telephony network  12  includes a Serving GPRS Service Node (SGSN)  23  that exchanges information with RNC  23  in communicates with the IWU  18  of the WLAN  10  through the port  21 . Typically, the wireless telephony network  12  can include a plurality of SGSNs but only a single SGSN  23  appears in FIG. 1 for purposes of simplicity.  
         [0018]    In practice, each SGSN, such as SGSN  23 , acts as a control hub for the wireless telephony network  12 . To that end, each SGSN has the necessary infrastructure (interfaces) and logic (communications protocols) to manage not only a plurality of mobile terminals (not shown) in direct contact with the wireless telephony network  12 , but also to manage each MT, such as MT  14 , in communication with the wireless telephony network  12  through the WLAN  10 . Associated with the SGSNs in the wireless telephony network  12 , such as SGSN  23 , is a home location register (HLR)  24  that includes a database (not shown) for storing information about each MT, including each MT (e.g., MT  14 ) that accesses the wireless telephony network  12  through the WLAN  10 .  
         [0019]    As indicated, each SGSN, such as SGSN  23 , includes the necessary interfaces and protocols to support the exchange of control information with one or more mobile terminal users (not shown) in direct communication with the wireless telephony network  12 . Thus, each SGSN, such as the SGSN  23 , has the capability of handling control information transmitted across GPRS channel, such as channel  20 . Therefore, utilizing the GPRS channel  20  to carry control information between the WLAN  10  and the wireless telephony network  12  does not require the addition of new interfaces or new protocols.  
         [0020]    In practice, interworking of the WLAN  10  and the wireless network  12  relies on different protocols for communication of different types of control information. FIG. 2 depicts the protocol stacks for the MT  14 , AP  16 , IWU  18  and SGSN  23  associated with the use of the AAA protocol as the top level protocol for communicating authentication, authentication and accounting information. As seen in FIG. 2, the MT  14  has a protocol stack  26  at the top of which resides the AAA protocol. Beneath the AAA protocol resides a signaling protocol via which the MT  14  exchanges signaling information with the AP  16  and/or the IWU  18 . Beneath the signaling protocol in the stack  26  of the MT  14  resides a WLAN radio protocol, which the MT  14  utilizes to undertake RF communications with the WLAN  10 .  
         [0021]    The AP  16  has a protocol stack  28  at the top of which typically resides the signaling protocol for enable the exchange of signaling information with the MT  14 . Beneath the signaling protocol in the stack  28  resides the WLAN radio protocol for facilitating RF communication with the MT  14 . The protocol stack  28  of the AP  16  also carries an Ethernet communications protocol at the same level as the WLAN radio protocol to enable the AP  16  to exchange Ethernet communications with the IWU  18 . In the illustrated embodiment of FIG. 1 wherein the AP  16  and the IWU  18  exist as separate entities, the protocol stack  28  within AP  16  does not contain the AAA protocol because there is no need for AP  16  itself to perform any operation on the AAA information from MT  14 , other than to pass such information to the IWU  18 .  
         [0022]    The IWU  18  has a protocol stack  30  at the top of which resides the AAA protocol to enable the IWU  18  to negotiate authorization and authentication of the MT  14  with the SGSN  23  in the wireless telephony network  12 . Immediately beneath the AAA protocol in the stack  30  resides a user plane that includes the signaling protocol and the UDP/IP (User Datagram Protocol/Internet Protocol), the latter being used for formatting messages for exchange with the wireless telephony network  12 . At the next lower layer (the control plane), the protocol stack  30  carries Ethernet protocol and the GPRS protocol. The GPRS protocol enables the IWU  18  to interface with the wireless telephony network  12 .  
         [0023]    The SGSN  23  has a protocol stack  32  whose upper-most layer carries the AAA protocol. The protocol stack  32  carries the UDP/IP beneath the AAA protocol. Lying beneath the UDP/IP, the protocol stack  32  carries the GPRS protocol that is distributed among several elements in the wireless telephony network. At the same layer as the AAA protocol, the SGSN protocol stack  32  includes a core network AAA protocol, typically gathered from the other protocols in the stack to enable the SGSN  23  to interact with the wireless telephony network  12  to accomplish authorization, authentication and accounting.  
         [0024]    Rather than utilize the AAA protocol as illustrated in FIG. 2 as the top-level protocol for authentication, other protocols can be used. In an alternate preferred embodiment depicted in FIG. 3, the MT  14  protocol stack  26  carries the Equivalent Access (EA) protocol at its top level for handing both authentication and signaling communications. Beneath the EA protocol resides the WLAN radio protocol as described previously. The protocol stack  28  of the AP  16  of FIG. 3 carries the EA protocol at its top level to permit interfacing with the MT  14 . Further, the top level of the protocol stack  28  of the AP  16  includes the well-known Remote Authentication Dial-In User Service (RADIUS) protocol, which the AP  16  uses to interact with the SGSN  23 . Immediately beneath the RADIUS protocol in the protocol stack  28  of the AP resides the UDP/IP. The WLAN protocol resides beneath the EAP in the protocol stack  28  of the AP  16  for enabling the AP  16  to manage the WLAN radio communications. The Ethernet protocol resides at the same level in the protocol stack  28  as the WLAN protocol for enabling the AP  16  to manage Ethernet communications with the IWU  18 .  
         [0025]    The IWU  18  of FIG. 3 has a protocol stack  30  that carries the UDP/IP at its top level for handling signaling-type communications between the AP  16  and the SGSN  23 . Beneath the UDP/IP in the protocol stack  30  of the IWU  18  resides the Ethernet protocol for enabling the IWU to manage Ethernet communications of packets with the AP  16 .  
         [0026]    The SGSN  23  of FIG. 3 has a protocol stack  32  at the top of which resides the RADIUS protocol for handling access authentication with the AP  16 . Lying beneath the RADIUS protocol in the protocol stack  32  is the UDP/IP protocol. Also lying beneath the RADIUS protocol is a GPRS Interface protocol via which the SGSN  23  manages the GPRS functions in the wireless network  12  of FIG. 1.  
         [0027]    [0027]FIG. 4 illustrates the use a GMM-like protocol as the top-level protocol for authentication. As seen in FIG. 4, the protocol stack  26  of the MT  14  carries the GMM-like protocol at the top level to enable the MT  14  to pass authentication information to the SGSN  23  with no intervention by the AP  16  or the IWU  18 . Lying beneath the GMM-like protocol within the protocol stack  26  of the MT  14  is the signaling protocol to enable the MT to exchange signaling information with the IWU  18 . Beneath the signaling protocol in the protocol stack  26  is the WLAN radio protocol as described previously.  
         [0028]    The AP  16  has a protocol stack  28  that contains the WLAN radio protocol at its top level for managing the radio communications between the WLAN  10  and the MT  14 . The protocol stack  28  of the AP  16  also contains the Ethernet protocol for enabling the AP to communicate with the IWU  18  via Ethernet-formatted signals. Note that protocol stack  28  of the AP  16  of FIG. 4 lacks both the GMM-like protocol and the signaling protocol because in this illustrative embodiment, authentication information from the MT  14  passes to the SGSN  23  without processing by either the AP  16  or the IWU  18 .  
         [0029]    The IWU protocol stack  30  has the signaling protocol and the UDP/IP at its top level to facilitate the communication of signaling information between the MT  14  and the SGSN  23 . Beneath the Signaling and UDP/IP protocols, the IWU protocol stack  30  carries the Ethernet protocol and the GPRS protocols as discussed.  
         [0030]    The SGSN protocol stack  32  carries the GMM-like protocol at its upper-most level to facilitate the exchange of authentication information with the MT  14 . Below the GMM-like protocol, the SGSN protocol stack  32  contains the UDP/IP and the GPRS protocol as well as the GPRS interface protocol stack.  
         [0031]    The foregoing describes a technique for interworking a WLAN with a wireless telephony network to provide a tight coupling therebetween via a GPRS channel so as to obtain security comparable to a leased line connection but without the associated cost.