Abstract:
A method and apparatus for supporting routing area (RA) update in a long term evolution (LTE) general packet radio service (GPRS) tunneling protocol (GTP)-based system are disclosed. A wireless transmit/receive unit (WTRU) sends an RA update request to a new evolved Node-B (eNodeB) and a mobility management entity (MME). The MME sends an update packet data protocol (PDP) context request to an access gateway (AGW), whereby a new tunnel is established between the new eNodeB and the AGW. For an inter-MME routing area update, the WTRU sends an RA update request to a new eNodeB and a new MME. The new MME sends an MME context request to an AGW. The AGW sends an MME context response to the new MME. The new MME sends an update PDP context request to the AGW, whereby a new tunnel is established between the new eNodeB and the AGW.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/793,289 filed Apr. 19, 2006, which is incorporated by reference as if fully set forth. 
     
     FIELD OF INVENTION 
       [0002]    The present invention is related to a wireless communication system. More particularly, the present invention is related to a method and apparatus for supporting routing area update (RAU) in a long term evolution (LTE) general packet radio service (GPRS) tunneling protocol (GTP)-based system. 
       BACKGROUND 
       [0003]      FIG. 1  shows a conventional GPRS/third generation ( 3 G) wireless communication system architecture  100  that shows various interfaces/protocols as well as user data transfer interfaces between various network entities. The wireless communication system  100  includes at least one serving GPRS support node (SGSN)  105  and at least one gateway GPRS support node (GGSN)  110 . The wireless communication system  100  further comprises a universal terrestrial radio access network (UTRAN)  115  which includes one or more radio access networks (RANs), base station systems (BSSs) and radio network controllers (RNCs), (not shown). The system  100  also comprises a plurality of wireless transmit/receive units (WTRUs)  120 , each including a terminal equipment (TE)  125  coupled to a mobile terminal (MT)  130 . The mobility in the wireless communication system  100  is facilitated by anchoring an Internet Protocol (IP) session at the GGSN  110  and allowing for multi-level mobility by supporting mobility management (MM) protocols for IP and non-IP traffic/services provided by the SGSN  105 . 
         [0004]      FIG. 2A  shows how dual tunnels are established in the conventional wireless communication system  100  of  FIG. 1  to provide IP connectivity for user plane traffic. As shown in  FIG. 2A , a GPRS tunnelling protocol (GTP) user plane (GTP-U) tunnel  220  is established between a GGSN  205  and an SGSN  210 , and a second user plane tunnel  225  is established between the SGSN  210  and a radio network controller (RNC)  215 . Both tunnels are dedicated to the same user. The GTP tunnel  220  has a user plane and a control plane. The user tunnel  225  is an IP tunnel having a user plane and a RAN application part (RANAP) control plane used for control messaging. 
         [0005]      FIG. 3  shows the system architecture evolution (SAE) of a long term evolution (LTE)-based network with various interfaces/protocols as well as user data transfer interfaces between various network entities. The wireless communication system  300  includes an evolved packet core  305  comprising at least one mobility management entity (MME)/user plane entity (UPE)  310  and at least one inter-access system (AS) anchor  315 , also called an access gateway (AGW). An evolved radio access network  320  includes at least one evolved Node-B (eNodeB). The wireless communication system  300  further comprises a GPRS core  325  as described above with reference to  FIG. 1 , which includes at least one universal terrestrial radio access network (UTRAN)  330 , and at least one GPRS enhanced data rates for global system for mobile communications (GSM) evolution (EDGE) radio access network (GERAN)  335 . Mobility of WTRUs (not shown) in the wireless communication system  300  is facilitated by anchoring Internet Protocol (IP) sessions at the AGW  315  and allowing for multi-level mobility by supporting mobility management (MM) protocols for IP traffic/services provided by the AGW  315 . 
         [0006]    LTE based networks are the evolution toward all IP Networks (AIPNs). IP traffic generated from the network operator, such as instant messaging, and non third generation partnership project (3GPP) IP traffic, (i.e., wireless local area network (WLAN) traffic), is anchored and routed through the AGW  315 . 
         [0007]    A routing area update (RAU) is used to minimize the paging traffic within a wireless communication system that is grouped into clusters. Each cluster includes a group of cells (Node-Bs). Each cluster is defined by a unique identifier, (i.e., routing area identifier (ID)). Those WTRUs in the wireless communication system that travel across boundaries of the clusters have to perform a registration process called a routing area update. In the RAU, the WTRU informs the core network regarding which area of the system it is operating in. If the WTRU receives a terminated call, the core network pages the WTRU in the last known routing area. This eliminates the need to send a paging message for the WTRU throughout the entire system, which in turn significantly reduces the amount of signalling across the system. Thus, more processing power is allocated to user traffic. The RAU may require the establishment of a new connection between a GGSN and a new RNC. New processes and message formats are needed for a single tunnel approach as compared to those existing in a two tunnel approach. 
         [0008]    One objective in LTE is to facilitate mobility and reducing development cost by anchoring IP sessions at the access gateway (AGW) and allowing for multi-level mobility and supporting existing GPRS/3G mobility management (MM) protocols. In LTE, most of the services and applications are migrating toward IP-based platforms. This migration requires IP connectivity and the traffic generated does not have be terminated at a mobility management entity (MME)/user plane entity (UPE), as it is the case in GPRS. 
       SUMMARY 
       [0009]    The present invention is related to a method and apparatus for supporting routing area update in an LTE GTP-based system. In accordance with the present invention, a single GTP tunnel is established between an AGW and an eNodeB. A WTRU sends a routing area update request to a new eNodeB, which forwards the routing area update request to an MME. The MME sends an update packet data protocol (PDP) context request to an AGW, whereby a new tunnel is established between the new eNodeB and the AGW. For an inter-MME routing area update, the WTRU sends a routing area update request to a new eNodeB, which forwards the routing area update request to a new MME. The new MME sends an MME context request to an AGW. The AGW sends an MME context response to the new MME. The new MME sends an update PDP context request to the AGW, whereby a new tunnel is established between the new eNodeB and the AGW. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A more detailed understanding of the invention may be had from the following description of a preferred embodiment, given by way of example and to be understood in conjunction with the accompanying drawings wherein: 
           [0011]      FIG. 1  shows a conventional GPRS/3G wireless communication system architecture; 
           [0012]      FIG. 2A  shows establishment of a conventional GTP user plane tunnel; 
           [0013]      FIG. 2B  shows establishment of a single GTP tunnel in accordance with the present invention; 
           [0014]      FIG. 3  shows the system architecture evolution (SAE) of an LTE-based wireless communication system; 
           [0015]      FIG. 4  shows a conventional tunnel protocol stack; 
           [0016]      FIG. 5  shows an LTE GTP protocol stack in accordance with the present invention; 
           [0017]      FIG. 6  is a flow diagram of a conventional tunnel establishment procedure; 
           [0018]      FIG. 7  is a flow diagram of an LTE single GTP tunnel establishment (LTE attach) procedure in accordance with the present invention; 
           [0019]      FIG. 8  shows a GTP intra-eNode intra-MME RA update in accordance with the present invention; 
           [0020]      FIG. 9  is a flow diagram of a process for intra-MME RA update in accordance with the present invention; 
           [0021]      FIG. 10  shows an inter-MME RA update for an LTE GTP-based system in accordance with the present invention; and 
           [0022]      FIGS. 11A and 11B , taken together, are a flow diagram of a process for inter-MME RA update in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    When referred to hereafter, the terminology “wireless transmit/receive unit (WTRU)” includes but is not limited to a user equipment (UE), a mobile station, a fixed or mobile subscriber unit, a pager, a cellular telephone, a personal digital assistant (PDA), a computer, or any other type of user device capable of operating in a wireless environment. When referred to hereafter, the terminology “base station” includes but is not limited to a Node-B, a site controller, an access point (AP), or any other type of interfacing device capable of operating in a wireless environment. 
         [0024]    The features of the present invention may be incorporated into an integrated circuit (IC) or be configured in a circuit comprising a multitude of interconnecting components. 
         [0025]    In accordance with the present invention, the mobility in GPRS, ( 3 G or beyond), systems is facilitated by anchoring the IP session at the home GGSN and allowing for multi-level mobility, and by supporting existing MM protocols for non-IP traffic/services provided by the SGSN. 
         [0026]      FIG. 2B  shows a single user-plane tunnel approach in accordance with the present invention. A single user plane tunnel  260  is used to reduce the delay and processing power of an MME/UPE  255 . In the two-tunnel approach shown in  FIG. 2A , the SGSN  210  terminates both the GTP tunnel  220  and a user plane tunnel  225  to the RNC  215 , which means that the SGSN  210  decodes the packets traveling in both directions and translates them into the different protocol formats of the two tunnels  220  and  225 . In a single tunnel approach shown in  FIG. 2B , the MME/UPE  255  only establishes a tunnel between the AGW  265  and the eNodeB  250  via two separate interfaces/protocols, (RANAP-C and GTP-C). In the single tunnel approach, the MME/UPE  255  is not involved in the user plane traffic. Thus, the user traffic passes through the MME/UPE  255  unchanged, (i.e., unaltered), in both directions. Only the eNodeB  250  and the AGW  265  are allowed to perform/act on the user plane traffic. The MME/UPE  255  only manages the control traffic, including MM, RAU, and the like, associated with the user and its IP based traffic. The MME/UPE  255  connects an eNodeB  250  and an AGW  265  using a GTP control plane to communicate with the AGW  265  and a RANAP control plane to communicate with the eNodeB  250 . When a handoff occurs between eNodeBs, the MME/UPE  255  is responsible for providing the AGW  265  with the new eNodeB TEID information and the establishment of the single tunnel  260 . 
         [0027]      FIG. 4  shows a prior art tunnel protocol stack according to existing GPRS protocol. A GTP-U tunnel transfers, (i.e., tunnels), user data between a UTRAN (which includes RANs, BSSs and RNCs) and a 3G-SGSN, and between the 3G-SGSN and a 3G-GGSN. 
         [0028]      FIG. 5  shows tunnel protocol stack in accordance with the present invention, in which the user plane tunnel is established between an eNodeB and an AGW. The IP Tunnel shown in  FIG. 5  can be GTP-based or any generic IP-Tunnel. In a preferred embodiment, the GTP-U tunnel is used as an IP tunnel. 
         [0029]      FIG. 6  is a conventional signaling diagram of a process for single tunnel establishment. The single tunnel functionality reduces the delay and processing power at the SGSN by reducing the need for protocol translation between the RNC and GGSN interfaces, and by enabling direct user plane tunnel between the RAN/RNC and the GGSN within the packet switched (PS) domain. However, the single tunnel approach will not eliminate the need for the SGSN to manage control traffic for IP-based traffic. The SGSN is still needed for the control plane signalling, MM and call/session management, and the SGSN makes a decision as to whether to establish a single tunnel or establish dual tunnels. 
         [0030]    In the case of a single tunnel, the SGSN should connect the RAN/RNC TEID and the GGSN TEID for user plane by informing each end point of the tunnel of the corresponding TEID of the other end point, (i.e., informing the GGSN of the RNC TEID and informing the RNC of the GGSN TEID). In the case of a handoff between RNCs, the SGSN is responsible for updating and providing the GGSN with new RNC TEID information and the establishment of the single tunnel. 
         [0031]      FIG. 7  shows an LTE single GTP tunnel establishment (LTE attach) procedure  700 , (packet data protocol (PDP) context activation), which is implemented in a wireless communication system including a WTRU  705 , an eNodeB  710 , an MME/JPE  715  and an AGW  720  in accordance with the present invention. The WTRU  705  sends an LTE attach request message to the eNodeB  710  and the MME/UPE  715  that includes PDP type, PDP address, APN, quality of service (QoS) data and the like (step  725 ). The MME of the MME/UPE  715  validates the LTE attach request, selects an APN, and maps the APN to the AGW  720  (step  730 ). The MME/UPE  715  determines if a single tunnel is supported and/or requested, and notes the existence of GTP TEIDs (step  730 ). The MME/UPE  715  creates a PDP context request that includes PDP Type, PDP Address, APN, an eNodeB TEID, QoS and the like (step  735 ). The AGW  720  creates a PDP context response that includes PDP Type, PDP Address, APN, an indicator that the establishment of the GTP tunnel is granted, AGW TEID, QoS and the like (step  740 ). The WTRU  705  and the eNodeB  710  establish a radio access bearer (RAB) (step  745 ). In step  750 , the MME/UPE  715  and the eNodeB  710  exchange tunnel setup signaling that includes a mobile station international subscriber directory number (MSISDN), a PDP address and an AGW TEID, and the MME/UPE  715  sends tunnel establishment information to the eNodeB  710  after receiving an indication of acceptance from the AGW  720  to establish the tunnel. The MME/UPE  715  sends an update PDP context request to the AGW  720  (step  760 ) to establish the new tunnel by informing the AGW  720  of the AGW TEID associated with the request, and the AGW  720  sends an update PDP context response to the MME/UPE  715  (step  765 ) confirming/rejecting the establishment of the tunnel and the associated attributes, (RNC TEID, PDP type, PDP address, user ID, and the like). The MME/UPE  715  inserts the AGW address in its PDP context, sends the PDP address received from the AGW  720  (step  770 ) and prepares for the response to be sent down to the WTRU  705 . Thus, if necessary, the MME/UPE  715  updates the PDP context in the AGW  720  to reflect any changes in the QoS attributes resulting from the RAB establishment of step  745 . Tunnel establishing signaling is exchanged between the eNodeB  710  and the AGW  720  including the MSISDN, PDP address, eNodeB TEID and AGW TEID (step  775 ). The MME/UPE  715  sends an activate PDP context accept signal to the WTRU  705  that indicates the presence of a single tunnel (step  780 ). 
         [0032]      FIG. 8  shows a GTP intra-eNode intra-MME RA update in accordance with the present invention. 
         [0033]      FIG. 9  shows a GTP intra-eNodeB intra-MME routing area update procedure  900 , which is implemented in a wireless communication system including a WTRU  905 , an old eNodeB  910 , a new eNodeB  915 , an MME  920 , an AGW  925  and a home location register (HLR)  930  in accordance with the present invention. 
         [0034]    Still referring to  FIG. 9 , an old tunnel is established between the old eNodeB  910  and the AGW  925  (step  935 ). The WTRU  905  sends a routing area update (EAU) request, which may include a packet temporary mobile subscriber identity (P-TMSI), old routing area identification (RAI), old P-TMSI signature, an update type and the like, to the new eNodeB  915  and the MME  920  (step  940 ). The update type indicates whether or not the routing area update is periodic. Security functions are then established between the WTRU  905 , the MME  920  and the HLR  930  (step  950 ). The MME  920  sends an update PDP context request to the AGW  925  (step  955 ). The AGW  925  then sends an update PDP context response to the MME  920  (step  960 ). The MME  920  sends a tunnel establishment request to the new eNodeB  915  (step  965 ). In step  955 , the MME  920  establishes the new tunnel between the AGW  925  and the new eNodeB  915  by sending the TEID of the new eNodeB  915  to the AGW  925  in the update PDP context request of step  955 . If the request is granted, the AGW  925  confirms the request back to the MME  920  in step  960 . In step  965 , the MME  920  establishes the other end of the tunnel to the new eNodeB  915  by sending the TEID of the AGW  925  to the new eNodeB  915  via the tunnel establishment request message. In step  970 , the new eNodeB  915  acknowledges the request and indicates the operation success to the MME  920  by sending a tunnel establishment response message. Now, a new tunnel is established in step  975 . 
         [0035]    Optionally, there may be additional update PDP context requests depending on the final set of QoS attributes. The new eNodeB  915  then sends a tunnel establishment response to the MME  920  (step  970 ). A new tunnel between the new eNodeB  915  and the AGW  925  is then established (step  975 ). Upon the successful establishment of the new tunnel, the MME  920  releases the old tunnel by sending a release request to the old eNodeB  910  in step  980 . A release response is sent from the old eNodeB to the MME  920  (step  985 ). A routing area update accept is sent from the MME  920  to the new eNodeB  915  and the WTRU  905  (step  990 ). A routing area update complete message is then sent from the WTRU  905  to the new eNodeB  915  and the MME  920  (step  995 ). 
         [0036]      FIG. 10  shows an inter-MME RA update for an LTE GTP-based system in accordance with the present invention. 
         [0037]      FIGS. 11A and 11B , taken together, show an LTE GTP intre-MME routing area update procedure  1100 , which is implemented in a wireless communication system including a WTRU  1105 , an old eNodeB  1110 , a new eNodeB  1115 , a new MME  1120 , an old MME  1125 , an AGW  1128  and an HLR  1130  in accordance with the present invention. 
         [0038]    Referring to  FIG. 11A , an old tunnel is established between the old eNodeB  1110  and the AGW  1128  (step  1132 ). The WTRU  1105  sends a routing area update request, which may include a P-TMSI, old RAI, old P-TMSI signature, an update type and the like, to the new eNodeB  1115  and the new MME  1120  (step  1134 ). The update type indicates whether or not the routing area update is periodic. The new MME  1120  sends an MME context request to the old MME  1125  (step  1136 ). The old MME  1125  sends an MME context response to the new MME  1120  (step  1138 ). Security functions are then established between the WTRU  1105 , the new MME  1120  and the HLR  1130  (step  1140 ). The new MME  1120  sends an MME context acknowledge message to the old MME  1125  (step  1142 ) and sends an update PDP context request to the AGW  1128  (step  1144 ) which indicates a single tunnel and the TEID of the new eNodeB  1115 . The AGW  1128  then sends an update PDP context response to the new MME  1120  (step  1146 ). The new MME  1120  sends a tunnel setup message to the new eNodeB  1115  which indicates the MSISDN, PDP address and the eNodeB TEID (step  1148 ). The new eNodeB  1115  then sends a tunnel setup acknowledgement message to the new MME  1120  (step  1150 ). A new tunnel between the new eNodeB  1115  and the AGW  1128  is then established (step  1152 ). 
         [0039]    In the case of pending traffic in the system using the old tunnel, the traffic is forwarded from the old eNodeB  1110  to the new eNodeB  1115  for service continuity. Referring to  FIG. 7B , after the new tunnel is established, forward packets are sent from the new MME  1120  to the old MME  1125  (step  1154 ). In step  1156 , forward packets are sent from the old MME  1125  to the old eNodeB  1110 . In step  1158 , packets are forwarded from the old eNodeB  1110  to the new eNodeB  1115 . In step  1160 , the old eNodeB  1110  sends a forward packets acknowledgement message to the old MME  1125 . In step  1162 , the old MME  1125  sends a forward packets acknowledgement message to the new MME  1120 . In step  1164 , the new MME  1120  sends an update location message to the HLR  1130 . In step  1166 , the HLR  1130  sends a cancel location message to the old MME  1125 . In step  1168 , release signaling, (e.g., a release request message and a release response message), is exchanged between the old eNodeB  1110  and the old MME  1125 . In step  1170 , a cancel location acknowledgement message is sent from the old MME  1125  to the HLR  1130 . In step  1172 , insert subscriber data is sent from the HLR  1130  to the new MME  1120 . In step  1174 , the new MME  1120  sends an insert subscriber data acknowledgement message to the HLR  1130 . In step  1176 , the HLR  1130  sends an update location acknowledgement message to the new MME  1120 . In step  1178 , the new MME  1120  sends a routing area update accept message to the new eNodeB  1115  and the WTRU  1105 . In step  1180 , the WTRU  1105  sends a routing area update complete message to the new eNodeB  1115  and the new MME  1120 . 
         [0040]    Although the features and elements of the present invention are described in the preferred embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the preferred embodiments or in various combinations with or without other features and elements of the present invention. The methods or flow charts provided in the present invention may be implemented in a computer program, software, or firmware tangibly embodied in a computer-readable storage medium for execution by a general purpose computer or a processor. Examples of computer-readable storage mediums include a read only memory (ROM), a random access memory (RAM), a register, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks, and digital versatile disks (DVDs). 
         [0041]    Suitable processors include, by way of example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors in association with a DSP core, a controller, a microcontroller, Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs) circuits, any other type of integrated circuit (IC), and/or a state machine. 
         [0042]    A processor in association with software may be used to implement a radio frequency transceiver for use in a wireless transmit receive unit (WTRU), user equipment (UE), terminal, base station, radio network controller (RNC), or any host computer. The WTRU may be used in conjunction with modules, implemented in hardware and/or software, such as a camera, a video camera module, a videophone, a speakerphone, a vibration device, a speaker, a microphone, a television transceiver, a hands free headset, a keyboard, a Bluetooth® module, a frequency modulated (FM) radio unit, a liquid crystal display (LCD) display unit, an organic light-emitting diode (OLED) display unit, a digital music player, a media player, a video game player module, an Internet browser, and/or any wireless local area network (WLAN) module.