Abstract:
A system and method for fast GPRS for IPv6 may improve data transfer efficiency in mobile networks, for example, in networks that relay on the GPRS infrastructure as defined and standardized in the European Telecommunications Standards Institute (ETSI), and on mobile IPv6 as standardized in the IETF. Mobile IPv6 techniques may be applied in the context of GPRS to transform mobility management into a routing problem, for example, by translating the routing area identifier into a part of the routing prefix in IPv6. Similar mobile IPv6 techniques also may provide an evolution path toward internetworking using native mobile IPv6.

Description:
RELATED APPLICATION 
   This utility patent application is a continuation of a previously filed U.S. provisional patent application, U.S. Ser. No. 60/271,190 filed on Feb. 23, 2001, the benefit of the filing date of which is hereby claimed under 35 U.S.C. §119(e). 

   FIELD OF THE INVENTION 
   This invention relates generally to data transfer efficiency and more specifically, to data transfer efficiency in GPRS cellular networks. 
   BACKGROUND OF THE INVENTION 
   General Packet Radio Service (GPRS) systems such as Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) currently rely on two network elements: a serving GPRS support node (SGSN) and a gateway GPRS support node (GGSN). A tunneling protocol called the GPRS tunneling protocol (GTP) typically handles the correspondent flows between the SGSN and the GGSN. One GGSN typically routes traffic between a mobile node on the GPRS system and the correspondent flows on the GTP tunnel. Routing the mobile node traffic and the correspondent flows through one GGSN causes inefficiency in the routing of data within the GPRS system. 
   Currently available methods for streamlining routing include the application of mobile Internet Protocol Version 6 (IPv6) mechanisms. However, there is currently no means for GPRS systems to exploit the packet transfer acceleration opportunities provided by mobile IPv6. A desirable goal would be to increase the efficiency and cost effectiveness of the GPRS solution to mobility management. 
   SUMMARY OF THE INVENTION 
   A system and method for fast GPRS for IPv6 is disclosed in which data transfer efficiency is improved in cellular networks. In an embodiment of the present invention, the cellular network relies on the GPRS infrastructure as defined and standardized in the European Telecommunications Standards Institute (ETSI), and on mobile IPv6 as currently being standardized in the Internet Engineering Task Force (IETF). Mobile IPv6 techniques may be applied in the context of GPRS to transform mobility management into a routing problem. For example, in an embodiment of the present invention, the routing area identifier is translated into a part of the routing prefix in IPv6. Similar mobile IPv6 techniques also may provide an evolution path toward internetworking using native mobile IPv6. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram illustrating a GPRS system for GSM; 
       FIG. 2  is a diagram illustrating a system for fast GPRS for GSM; 
       FIG. 3  is a diagram illustrating a GPRS system for UMTS; 
       FIG. 4  is a diagram illustrating a system for fast GPRS for UMTS; 
       FIG. 5  is a diagram illustrating contents of an exemplary packet format for router advertisements in a system and method for fast GPRS; 
       FIG. 6  is a diagram illustrating an example of prefix information coding in a system and method for fast GPRS; 
       FIG. 7  is a diagram illustrating contents of an exemplary routing area identification information element in a system and method for fast GPRS; 
       FIG. 8  is a diagram illustrating a table showing exemplary routing area update request message content in a system and method for fast GPRS, in accordance with the present invention; and 
       FIG. 9  is a diagram illustrating an exemplary mobile node. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A system and method for Fast GPRS for IPv6 in accordance with an embodiment of the present invention is disclosed herein. In the following description, numerous specific details are set to provide a thorough understanding of the present invention. However, it will be evident to those skilled in the art that these specific details need not be used to practice the present invention and alternative embodiments are possible. In other cases, well-known structures and circuitry have not been shown in detail to avoid unnecessarily obscuring the present invention. 
   In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanied drawings, which form a part hereof, and which is shown by way of illustration, specific exemplary embodiments of which the invention may be practiced. Each embodiment is described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
   Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.” The term “operator” refers to any technician or organization that maintains or services an IP packet based network. Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or is inconsistent with the disclosure herein. 
   The invention provides for accelerating packet transfer in GPRS systems with the use of a specific mobility management technique in mobile nodes. The invention has minimal impact on the GPRS node development. A minor modification to the GPRS core network (UTMS Radio Access Network “UTRAN” in UMTS and SGSN in GSM) is also necessary. The resulting system is more efficient and cost effective than the actual GPRS solution. The basic idea is that the routing area identifier is to be translated into a part of the routing prefix in IPv6. The result is a combined GPRS and IPv6 routing infrastructure. This enables IPv6 mobility to be used as an alternative to GPRS mobility. 
   Currently, GPRS (GSM/UMTS) systems such as those shown in  FIG. 1  and  FIG. 3  respectively, do not exploit the opportunities given by mobile IM, that transforms mobility management into a routing problem. In  FIG. 1 , the GSM system  100  includes MS (mobile node)  102 , BSS (Base Station Subsystem)  104 , SGSN  106 , and GGSN  108 . In  FIG. 3 , a UMTS system  300  includes MS (mobile node)  302 , UTRAN  304 , 3G-SGSN  306 , and 3G-GGSN  308 . 
   The current GPRS system relies on two network elements, SGSN  106 ,  306 , and GGSN  108 ,  308 , and the tunneling protocol called GTP between them (shown as GTP-U  110 ,  112 ,  310 ,  312 ). The traffic between the mobile node and the correspondent flows through a tunnel that is typically anchored into one GGSN  108 ,  308 . This causes inefficiency in the routing of data within the GPRS system. By applying mobile IPv6 more straightforward mechanisms a more streamlined routing could be achieved and also an evolution path towards interworking with native mobile IPv6 based networking could be accomplished. 
   The invention bypasses the usage of the GTP (in GSM) and GTP-U (in UMTS) protocol for data routing in GPRS. GTP is not specifically tailored for IP level mobility handing and is hence not optimal for native mobile IPv6 (or mobile IPv4). The technique that we propose is a “cut-through” in the GPRS network to extract IPv6 traffic out to the conventional Internet network before it enters into GTP. The proposed solution can co-exist with the GPRS network and relies on GPRS signaling, but handles traffic from mobile IPv6 capable nodes differently. For more information on GTP, see 3GPP TS 29.060 V3.6.0 (2000-09) Technical Specification Group Core Network; General Packet Radio Service (GPRS); GPRS Tunneling protocol (GTP) across the Gn and Gp Interface (Release 1999), which is herein incorporated by reference. 
   Example embodiments of systems for Fast GPRS for IPv6 in accordance with the present invention are shown in the block diagrams  200  and  400  of  FIG. 2  and  FIG. 4  respectively. In an embodiment of the present invention, an improvement is made to Mobile IPv6 by rapidly notifying the IPv6 layer of mobility within the cellular network, which improves GPRS routing and throughput by using Mobile IPv6 instead of GTP. (See  204  in the GSM type GPRS system  200  of  FIG. 2  and see  404  in the UMTS-type GPRS system  400  of  FIG. 4 .) An additional advantage of FAST GPRS is that it co-exists with the GPRS and it is hence possible to use at some times the FAST GPRS and in others come back to the conventional solution. Interworking between GPRS networks and native mobile IPv6 networks would be easier. For more information on combining GSM and Mobile IP Mobility Handling, see 3GPP Technical Specification Group Services and System Aspects; Combined GSM and Mobile IP Mobility Handling in UMTS IP (3G TR 23.923 version 3.0.0), which is herein incorporated by reference. In particular, 3G TR 23.923 version 3.0.0 discloses that Binding Update messages can include a mobile terminal&#39;s new care-of address (see, e.g., numbered page 70) and that a mobile terminal can generate and send a Binding Update message (see, e.g., FIG. A.5 on numbered page 71). 
     FIG. 4  is a diagram illustrating a system for fast GPRS for UMTS in accordance with an embodiment of the present invention. The Media Access Control (MAC) layer  206 ,  208 ,  404 ,  406 ,  408  in Fast GPRS nodes has the role of routing area advertisement translation from the GPRS system  200 ,  400  to the Mobile IPv6 router advertisements messages (ICMPv6). When the MS (mobile node)  302  receives a Routing area change notification from the SGSN  202  or UTRAN  402 , its MAC layer adaptation creates locally an IPv6 router advertisement message  500  to the IPv6 layer. The MAC layer adapter  404  uses Routing Area Identifier to create the needed prefix information element  600  for the IPv6 Router Advertisement message  500 . When the IPv6 layer of the mobile node receives this message it configures a new care of address based on the prefix  602  that was created by the MAC layer adapter. The IPv6 layer responds normally according to Mobile IPv6 specifications by sending a Binding Update. The MAC layer in the node encapsulates the binding update into the GPRS routing area request. For more information, see 3GPP TS 23.060 V3.5.0 (2000-10) Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS). Service Description (Release 1999), which is herein incorporated by reference. 
   For this there are at least two alternative embodiments. Either a new Information Element Identifier is introduced for Routing Area Update message that carries all mobile IPv6 signaling or a new Update type is introduced. In the latter case, this new Routing Area Update Request type should be set to a unique globally recognized (i.e. to be standardized and reserved for this purpose) value. For example, the value ‘11’, may be used in order to indicate that it is not a normal routing area update request, but that it needs specific processing for the mobile IPv6 context. This is described in more detail below. If the GPRS system does not recognize or support the request for a mobile IPv6 context set up, then the GPRS system rejects the special routing area update request and the mobile node falls back to the normal Packet Data Protocol (PDP) address activation process requesting IPv6 context from the normal GPRS. 
   In case the network recognizes the Fast GPRS routing area update request containing the Mobile lPv6 Binding Update, it is sent by the Access router (Radio Network Controller “RNC” in UMTS or SGSN in GSM) to its Home agent as part of standard mobile IP operation. All IP traffic that uses this mobile IPv6 PDP is extracted in SGSN (or alternatively in RNC) and routed directly into Internet. Note that the Mobile node should send (in case FAST GPRS routing area update request is accepted by the network) a second routing area update request with the type set to periodic or new routing area update to update the normal GPRS lower layers. 
     FIG. 9  illustrates an exemplary mobile node  902 , that includes a MAC layer module  904 , an IPv6 layer module  906 , and an encapsulation module  908 , arranged to perform the respective functions described herein. The mobile nodes  102 ,  302  can be implemented using the mobile node  902  and/or the structure shown in  FIG. 9 . 
     FIG. 8  is a table  800  showing examples of the message content of a Routing Area Update Request in a system and method for Fast GPRS in accordance with an embodiment of the present invention. 
   For authentication reasons, it is necessary to delay Mobile IPv6 Binding updates sent to the home agent until the GPRS authentication is verified. The sending of Binding Update Acknowledgement (BACK) should be delayed until Routing Area Update Accept message from a SGSN or RNC is sent. The BACK message is carried in the Routing Area Update Accept message. 
   The invention necessitates a MAC layer adapter in the Mobile node supporting IPv6 on top of GPRS. The role of this MAC layer adapter is to generate Internet Control Message Protocol (ICMP) v6 Router advertisement messages from GPRS Routing area update messages. The Prefix advertised by this router advertisement is taken from the GPRS MM (Mobility Management) layer and is called the Routing Area Identifier (RAI). An example of a Routing Area Identification information element identifier (IEI)  700  is shown in  FIG. 7 . The adapter converts the RAI into advertised network prefixes in the corresponding ICMPv6 Router Advertisement messages. 
   At the SGSN/RNC there is a substantially similar adapter layer that extracts Binding Update messages from the Routing area updates received by the mobile node. It creates standard Binding Update messages for the Home Agents. Here the Authentication Header is calculated based on the GPRS key distribution mechanism. 
   A second modification may be done in the UTRAN network side for UMTS and in the SGSN for GSM networks for the purpose of extracting IP traffic from the mobile IPv6 node. This can be done based on the specific PDP context that was activated, or alternatively, an SGSN/RNC could check the IPv6 source address of the packets received from the mobile node. If the source address contains a prefix under the responsibility of the SGSN or UTRAN, then the packet is simply routed out of the GPRS network into the Internal infrastructure. A mapping entry between the IPv6 address and mobile node is stored in the SGSN/UTRAN. Similarly, when packets arrive at the SGSN or UTRAN, the IPv6 layer fetches the adequate mobile node context and if it exists, forwards the IPv6 packet in the conventional SNDCP/PDCP layer format. From the network side (SGSN or RNC in UTRAN), special routing area update requests are received from a mobile node asking for the Fast GPRS service. With the normal GPRS identification procedure (Identification Request message), it is possible to poll the node to determine whether the equipment belongs to a particular party, manufacturer, or if the user has a license agreement with that party. Such identification procedures may be useful for a variety of reasons, including determining whether or not another party has implemented an embodiment of the present invention. 
     FIG. 5  is a diagram illustrating contents of an exemplary packet format  500  for router advertisements in a system and method for fast GPRS in accordance with an embodiment of the present invention. The packet format  500  for router advertisements is defined in RFC 2461. Since the mobile node&#39;s MAC layer generates the frame, the link local source address could set to zero or alternatively to a link local address that was derived from Routing Area Identifier. This is to distinguish between other router advertisements arriving from the GGSN or other routers. The Router Lifetime should contain the frequency with which the mobile node receives information about Routing Area Updates. Typically, this depends on the physical layer. No Reachable Time field should be set. The Retrans Timer contains the value that has been assigned for the Ready Timer Function inherent to GPRS Mobility Management. 
   The destination address contains the anycast all-nodes multicast address. The Hop Limit should be set to zero. The Prefix Information contains the Value and length of the prefix as deduced from the Routing Area Update. The Prefix information may be coded as shown in  FIG. 6 .  FIG. 6  is a diagram illustrating an example of prefix information coding in a system and method for fast GPRS in accordance with an embodiment of the present invention. 
   The L bit has to be set to one. The A bit has to be set to one. Valid Lifetime and Preferred Lifetime should be set to the Requested READY timer value from the GPRS environment. 
   The prefix value is literally taken from the RAI (Routing Area Identifier) as defined in the ETSI recommendations (23-060, 24008). The octets  2  to  7  are inserted in the Prefix so that the octet one represents the most significant octet and octet  7  the least significant. Choosing prefixes will depend on each operator&#39;s routing plan.  FIG. 7  is a diagram illustrating contents of an exemplary routing area identification information element in a system and method for fast GPRS in accordance with an embodiment of the present invention. Routing Area Identity (RAI), defined by an operator, identifies one or several cells. In one embodiment that employs GSM, RAI is broadcast as system information. In another embodiment that employs UMTS, RAI is broadcast to mobile nodes in Radio Resource Control (RRC) Idle mode, and is notified to mobile nodes in RRC Connected mode on established RRC connections as MM system information. The acronyms listed in the equations below are as follows: Location Area Identity (LAI), Mobile Country Code (MCC), Mobile Network Code (MNC), Link Access Control (LAC), Radio Admission Control (RAC), Cell Identity (CI), and Cell Global Identification (CGI)
 
 LAI=MCC+MNC+LAC.  
 
 RAI=MCC+MNC+LAC+RAC.  
 
 CGI=LAI+CI  ( GSM  only).
 
   When a packet is received in the Sub-network Dependent Convergence Protocol (SNDCP) layer for the SGSN, the source is checked before tunneling through GTP. If the mobile node sending the packet has made a Fast GPRS request, then the packet is taken out from the GPRS network and routed directly into the IPv6 Internet. The SGSN stores the correspondence between the Service Access Point (SAP), Temporary Logical Link Identity (TLLI) and GPRS context with the newly assigned IPv6 address. 
   When packets arrive from the IPv6 network with a destination prefix equal to that of the SGSN and the SGSN recognizes the Destination Address to be already registered and has an active IPv6 context with Fast GPRS functionality, it forwards the packet through the normal SNDCP encapsulation procedures. 
   The SGSN performs the authentication procedure, and the RNC performs the ciphering procedure based on the algorithm for UMTS. In one embodiment, the SGSN is third generation, i.e., 3G-SGSN. When the RNC in UTRAN receives a routing area update from a new mobile node, it checks if the Routing Area Update Request type corresponds to the FAST GPRS method. If so, the RNC forwards the Routing Area Update to the SGSN and when the Bearer Access is granted by the SGSN, the RNC applies the same procedure as in the GSM case: It looks for every PDCP packet coming from the node and pulls it out from the GPRS to the Internet. When packets are received for the specific mobile node from outside the network, the RNC determines if a bearer exists for that mobile node. If so, the RNC forwards the packet on top of the PDCP protocol using the appropriate compression as specified in the PDCP protocol. 
   The MAC procedures have been described above. The Binding Update messages may be sent at the frequency of the Routing Area Update Requests.  FIG. 8  is a diagram illustrating a table showing exemplary routing area update request (Fast GPRS) message content in a system and method for fast GPRS in accordance with an embodiment of the present invention. In one embodiment, the Binding Update is inserted in the Routing Area Update Request in the field number 31. In this case, the Update Type information element identifier (IEI) can be set to 11 to prevent confusion with non-Fast GPRS network elements. Alternatively, a new IEI that denotes mobile IPv6 binding update/acknowledgement messages can be allocated. The Routing Area Update Accept Message can be sent upon the reception of a Binding Acknowledgment from the Home Agent in Mobile IPv6 or sent directly to the node. In one embodiment, this choice (selection) is available to the operator. 
   The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.