Abstract:
A method for an Internet Protocol (IP) address allocation by an external packet data network ( 40 ) to a mobile station ( 10 ) unburdens the mobile station ( 10 ) of directly contacting the external network. The mobile station requests ( 51 ) the unique IP address. The mobile network ( 31 ) statefully obtains the unique IP address from an external network ( 40 ). The mobile network ( 31 ) then transmit the verified, unambiguous unique IP address to the mobile station ( 10 ).

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention pertains to communication systems and more particularly to a method for allocating a unique interface identifier to a mobile station.  
           [0002]    When a mobile station connects to a General Packet Radio Support (GPRS) or Universal Mobile Telecommunications Service (UMTS) network, the mobile station uses a PDP (packet data protocol) context activation procedure in order to establish an internet protocol connectivity with an external Packet Data Network (PDN). Present procedures for a mobile network (i.e. a GGSN, gateway GPRS support node) generate a unique mobile station interface identifier. This interface identifier is passed back to the mobile station during the PDP context activation.  
           [0003]    However, this interface identifier does not allow the mobile station to generate an address with a network prefix other than the one from the GGSN. This mobile interface identifier may not be consistent with the other networks controlled by the mobile network. Mobile stations require access to other packet data networks for various data functions provided by 2G, 2.5G and 3G, etc. External packet data networks typically employ strict control mechanisms over address assignment.  
           [0004]    Current procedures which allow a mobile station to access an external packet data network for an Internet Protocol Version 6 (IPv6) address require the mobile station to support separate stateful address autoconfigurations. The drawbacks of the current mobile station external PDN procedure are as follows. A mobile station must support an additional protocol such as DHCP (dynamic host configuration protocol) which adds to the complexity and cost of the mobile station. Since additional signaling is required over the air, the time between the request and the time the communication “payload” is actually transferred is increased; this is referred to as the post-dialing delay. Lastly, since the mobile station spends more time on the air, the power of the mobile station is not conserved.  
           [0005]    It is therefore highly desirable to have a stateful autoconfiguration procedure performed by a mobile network instead of a mobile station which allows stateless autoconfiguration without requiring the mobile station to support DHCP or any other stateful address configuration protocol required by the external network. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0006]    [0006]FIG. 1 is a block diagram of an IP address allocation for mobile terminals in accordance with the present invention.  
         [0007]    [0007]FIG. 2 is a message flow diagram of a procedure for allocation of IP address for mobile terminals in accordance with the present invention 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0008]    [0008]FIG. 1 is a block diagram of a mobile station access for internet protocol address allocation from an external packet data network  40 . As mobile station is used herein, it includes a cellular telephone, personal digital assistant, computer laptop, pager or other “intelligent” device. Mobile station  10  is coupled to tower  15  of RAN  15  (radio access network). This coupling is in the form of an over-the-air cellular link in the example shown in FIG. 1, the link is a cellular one. Tower  15  and RAN  20  form the basis of the cellular network with which mobile station interfaces. Although a terrestrial cellular network is shown, a satellite communication network or other IPV6 network, such as a wireless LAN, is a suitable equivalent.  
         [0009]    RAN  20  is coupled to SGSN (Signaling GPRS Support Node)  25  of core network  31 . Either an intra-operator or inter-operator backbone  30  connects SGSN  25  to GGSN  35  (Gateway GPRS Support Node). GGSN  35  interfaces with the packet data network  40  in a stateful address autoconfiguration procedure to obtain an internet protocol version 6 address for mobile station  10 . The internet protocol version 6 address is then relayed from packet data network  40  to GGSN  35  to mobile station  10 .  
         [0010]    [0010]FIG. 2 is a message flow diagram of an IP address allocation method for mobile terminals. Mobile station  10  requests a packet data protocol (PDP) context activation request  51  to SGSN  25 . The request is for connectivity between the mobile station  10  and an external packet data network  40 . The SGSN (Serving GPRS Support Node)  25  forwards the request for connectivity  52  to GGSN (Gateway GPRS Support Node)  35 . GGSN  35  examines the contents of the message. Based upon the message contents, the GGSN  35  determines that mobile station  10  needs an IPv6 address from the address space which is managed by the external packet data network  40 .  
         [0011]    The external PDN  40  requires the use of a stateful address autoconfiguration in order to obtain an IPv6 address. Acting on behalf of the mobile station  10 , GGSN  35  solicits the address of a DHCP (Dynamic Host Configuration Protocol) server  41  within PDN  40  with the DHCP solicit message  53 . PDN  40  responds to the request of GGSN  35  with a DHCP advertise message  54 . The advertise message provides the address of the DHCP server  41  to be used by GGSN  35 .  
         [0012]    Responsive to the advertise message  54  from the external network, the GGSN sends a DHCP request message  55  to the DHCP server  41  of PDN  40  requesting an IPv6 address. Packet data network  40  then responds with an IPv6 address assigned to mobile station  10 . Next, GGSN  35  performs a duplicate address detection (DAD)  57  procedure to validate the uniqueness of the IPv6 address.  
         [0013]    When GGSN  35  determines the address to be unique the GGSN transmits the interface identifier portion of the IPv6 address back to the mobile station  10  through SGSN  25 . GGSN  35  responds to the initial PDP context request  52  with a PDP context response message  58  which is transmitted to SGSN  25 . SGSN then transmits a context activation response message  59  to the mobile station  10  via the radio access network (RAN)  20 .  
         [0014]    After sending the PDP context resonse message  58 , the GGSN  35  also transmits a router advertisement message  60  to the SGSN  25 . Router advertisement message  60  includes the network prefix obtained from the IPv6 address assigned to mobile station  10  by the external PDN  40 . The mobile network comprising RAN  20 , SGSN  25  and GGSN  35  does not manage or control this particular prefix.  
         [0015]    Next, SGSN  25  transmits the router advertisement including PDN network prefix message  61  to mobile station  10 . When mobile station  10  receives the router advertisement message  61  from SGSN  25 , mobile station  10  performs a stateless autoconfiguration process. As a result, mobile station  10  creates the same IPv6 address as was assigned by PDN  40 . Mobile station  10  created this same IPv6 address without the need for duplicate address detection,  62 , since GGSN  35  has previously determined the uniqueness of the address. As a result, additional signaling over the air between the SGSN and mobile station  10  is alleviated.  
         [0016]    This allocation address procedure has the benefit of requiring mobile station  10  to support only one method of obtaining an IPv6 address, regardless of the network which allocates the address. Mobile station  10  is not required to support an additional procedure for stateful address autoconfiguration such as DHCP. Further since the GGSN  35  performs the duplicate address detection process, the mobile device(s)  10  do not need to verify the uniqueness of the address and additional over the air signaling is saved as a result. Lastly, since the duplicate address detection procedures are not performed by the mobile device, there is no need to broadcast neighbor solicitation messages to other mobile stations in order to verify the uniqueness of the IPv6 address. As a result, the mobile device&#39;s design is much simpler and considerable over the air message transmission time is saved, thereby greatly increasing the battery life of the mobile station.  
         [0017]    Although the preferred embodiment of the invention has been illustrated, and that form described in detail, it will be readily apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the present invention or from the scope of the appended claims.