Abstract:
A method and system for performing cell update and routing area (RA) update procedures while a wireless transmit/receive unit (WTRU) is in an idle state in a third generation (3G) long term evolution (LTE) wireless communication system. When the WTRU receives a page message or has data to transmit while the WTRU is in an idle state, the WTRU transitions to an active state and sends a cell update message to an evolved Node-B (eNode-B). The eNode-B forwards the cell update message to a mobility management entity (MME)/user plane entity (UPE). The MME/UPE changes the state of the WTRU to an active state and takes an action based on the cell update message. When the WTRU moves to a new RA, the WTRU sends an RA update message to the MME/UPE via the eNode-B. The MME/UPE updates the RA of the WTRU based on the RA update message.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. provisional application No. 60/763,526 filed Jan. 31, 2006, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention is related to a third generation (3G) long term evolution (LTE) wireless communication system. More particularly, the present invention is related to a method and system for performing cell update and routing area (RA) update procedures while a wireless transmit/receive unit (WTRU) is in an idle state in an LTE wireless communication system. 
       BACKGROUND 
       [0003]    Developers of 3G wireless communication systems are considering 3G LTE systems. A 3G LTE wireless communication system provides an enhanced air interface to handle higher data rates with more efficiency, reduction of the number of signaling procedures and setup delay, and a network design to permit interconnection and interoperation of any air interface, such as global standards for mobile communication (GSM), general packet radio services (GPRS), wideband code division multiple access (WCDMA), CDMA2000, IEEE 802.xx, or the like. 
         [0004]      FIG. 1  shows architecture for a 3G LTE wireless communication system  100 . The LTE wireless communication system  100  includes an evolved Node-B (eNode-B)  110 , an access gateway (aGW)  120  and a WTRU  130 . The aGW  120  includes a mobility management entity (MME)  122  and a user plane entity (UPE)  124 . Many of the functions of a radio network controller (RNC) in the conventional 3G system have been moved to the eNode-B  110 . 
         [0005]    The MME  122  manages and stores WTRU context, (e.g., WTRU and user identities, WTRU mobility state, user security parameters, or the like). The MME  122  generates temporary identities for the WTRU  130  and allocates them to the WTRU  130 . The MME  122  authenticates the user of the WTRU  130  and checks the authorization whether the WTRU  130  may camp on a certain tracking area (TA) or on a certain public land mobile network (PLMN). The MME  122  supports the mobility operation between different eNode-Bs  110  and maintains the seamless service continuity for the WTRU  130 . 
         [0006]    The UPE  124  terminates both downlink and uplink data paths for an LTE_Idle state of the WTRU  130 , and triggers and initiates paging when downlink data arrives for the WTRU  130 . The UPE  124  manages and stores WTRU contexts, (e.g., parameters of an Internet protocol (IP) bearer service and network internal routing information). 
         [0007]    Both the MME  122  and the WTRU  130  maintain an LTE state machine for mobility management as shown in  FIG. 2 . The state of the WTRU  130  may be one of an LTE_Detached state, an LTE_Idle state and an LTE_Active state. In an LTE_Detached state, the WTRU  130  is powered off and there is no RRC entity. At this state, the position of the WTRU  130  is not known to the system  100 . Upon power-up, the WTRU  130  makes a state transition from an LTE_Detached state to an LTE_Active state, and performs registration with the system  100 . 
         [0008]    During the transition from the LTE_Detached state to the LTE_Active state, the WTRU  130  establishes a mobility management (MM) state and obtains a packet data protocol (PDP) context. The WTRU  130  also obtains a security context, a radio resource control (RRC) context, a capability context, a quality of service (QoS) context, a radio bearer (RB) context, and temporary identities. A cell radio network temporary identity (C-RNTI), a tracking area identity (TA-ID), an IP address, or the like are allocated to the WTRU  130  and authentication and a security relation are established. At this point, the location of the WTRU  130  is known to the system  100  at a cell level. 
         [0009]    After registration, the WTRU  130  may be forced to transition to the LTE_Idle state from the LTE_Active state by the system  100  due to inactivity or other reason. The WTRU  130  may transition to the LTE_Idle state by itself. While the WTRU  130  is in the LTE_Idle state, the WTRU  130  is assigned a tracking area (TA) and the location of the WTRU  130  is known to the network at a TA level. 
         [0010]      FIG. 3  shows exemplary LTE routing areas (RAs). An LTE_Idle state function is handled by the MME and/or the UPE. It should be noted that  FIG. 3  shows three RAs as an example and any number and any levels of RAs may exist and any number of cells may be included in one RA. In  FIG. 3 , cells  1  and  2  are included in an LTE RA  1 , cells  2 - 4  are includes in an LTE RA  2 , and cells  4 - 6  are included in an LTE RA 3 . The cells are partially overlapped between adjacent RAs in order to avoid a ping-pong. 
         [0011]    While the WTRU  130  is in an LTE_Idle state, the WTRU  130  is required to make a fast transition to the LTE_Active state, (e.g., below 100 ms), when the transition is needed, (e.g., when the WTRU  130  receives a paging message). In addition, unnecessary traffic during the LTE_Idle state should be eliminated. 
         [0012]    Therefore, it would be desirable to provide a method and system for fast cell update and RA update while a WTRU  130  is in an LTE_Idle state. 
       SUMMARY 
       [0013]    The present invention is related to a method and system for performing cell update and RA update procedures while a WTRU is in an idle state in a 3G LTE wireless communication system. When the WTRU receives a page message or has data to transmit while the WTRU is in an idle state, the WTRU transitions to an active state and sends a cell update message to an eNode-B. The eNode-B forwards the cell update message to an MME/UPE. The MME/UPE changes the state of the WTRU to an active state and takes an action based on the cell update message. When the WTRU is in an idle state and moves to a new RA, the WTRU sends an RA update message to the MME/UPE via the eNode-B. The MME/UPE updates the RA for the WTRU based on the RA update message. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0014]    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: 
           [0015]      FIG. 1  shows a network architecture proposed for 3G LTE wireless communication system; 
           [0016]      FIG. 2  shows an LTE state machine; 
           [0017]      FIG. 3  shows exemplary LTE RAs; 
           [0018]      FIG. 4  is a signal flow diagram of a process for performing an LTE cell update in accordance with the present invention; 
           [0019]      FIG. 5  is a signal flow diagram of a process for performing an LTE cell update in accordance with another embodiment of the present invention; and 
           [0020]      FIG. 6  is a signal flow diagram of a process for performing an LTE RA update in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    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 “eNode-B” 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. 
         [0022]    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. 
         [0023]      FIG. 4  is a signal flow diagram of a process  400  for performing an LTE cell update procedure in accordance with the present invention. A WTRU  452  is currently in an LTE_Idle state, and the state of the WTRU is also set to an LTE_Idle state in an MME/UPE  456  (step  402 ). In an LTE_Idle state, the WTRU  452  operates in a discontinuous reception (DRX) mode camping on a paging channel. While the WTRU  452  is in an LTE_Idle state, an LTE cell update is performed autonomously. 
         [0024]    Upon receipt of incoming traffic for the WTRU  452  at step  404 , the MME/UPE  456  pages the WTRU  452  in an LTE RA for the WTRU  452 . The MME/UPE  456  sends a page message to an eNode-B  454  (step  406 ). The eNode-B  454  transmits the page message to the WTRU  452  (step  408 ). Upon receipt of the page message, the WTRU  452  transitions from the LTE_Idle state to an LTE_Active state (step  410 ). 
         [0025]    The WTRU  452  then sends a cell update message along with a page response message to the eNode-B  454  (step  412 ). The cell update message includes a temporary identity, (e.g., radio network temporary identity (RNTI)), of the WTRU  452  assigned by the MME/UPE  456 . The eNode-B  454  forwards the cell update message to a proper MME/UPE  456  based on the identity, (e.g., RNTI), (step  414 ). This makes it possible to support a multi-to-multi configuration between eNode-Bs and MME/UPEs. Multi-to-multi configuration refers to different deployment scenarios for MME/UPE, including a combination of the MME and the UPE in a single device and variations of separate MME and UPE, (e.g., a stand-alone MME/UPE separate from the aGW and a stand-alone MME with UPE included in the aGW where a single UPE supports multiple MMEs). 
         [0026]    After receiving the cell update message, the MME/UPE  456  changes the state of the WTRU  452  to an LTE_Active state (step  416 ) and sends a radio access bearer (RAB) establishment and cell update confirmation message to the eNode-B  454  (step  418 ). An RAB is then established between the eNode-B  454  and the WTRU  452  based on the RAB establishment message (step  420 ). The WTRU  452  then sends an RAB establishment and cell update complete message to the eNode-B  454  (step  422 ). The eNode-B  454  forwards the RAB establishment and cell update complete message to the MME/UPE  456  (step  424 ). User data is then communicated between the WTRU  452  and the MME/UPE  456  (step  426 ). 
         [0027]    The LTE cell update procedure may also be performed when the WTRU has pending traffic data to transmit, (i.e., data or signaling).  FIG. 5  is a signal flow diagram of a process  500  for performing an LTE cell update procedure in order to establish a proper RAB and an associated tunnel for the pending traffic in accordance with another embodiment of the present invention. A WTRU  552  is currently in an LTE_Idle state without an RAB or tunnel established, and the state of the WTRU  552  is also set to an LTE-Idle state in an MME/UPE  556  (step  502 ). 
         [0028]    When the WTRU  552  has data to transmit, the WTRU  552  transitions from the LTE_Idle state to an LTE_Active state (step  504 ). The WTRU  552  then sends a cell update message to the eNode-B  554  (step  506 ). The LTE cell update message includes information regarding the last RA update, (e.g., last RA identification or last cell update ID), along with a temporary identification, (e.g., RNTI), of the WTRU  552  assigned by the last serving MME/UPE  556 . The eNode-B  554  analyzes the last RA or cell update information to determine a proper serving MME/UPE, and then forwards the LTE cell update message to the proper MME/UPE  556  based on the identity, (e.g., RA ID, cell update ID, or RNTI), (step  508 ). 
         [0029]    After receiving the cell update message, assuming the same serving MME/UPE, (i.e., the same MME/UPE supported the eNode-B from which the WTRU&#39;s last communication), the MME/UPE  556  changes the state of the WTRU  552  to an LTE_Active state (step  510 ) and sends an RAB and tunnel establishment and cell update confirmation message back to the eNode-B  554  (step  512 ). A new tunnel is then established between the UPE  556  and the eNode-B  554 . A new RAB is also established between the eNode-B  554  and the WTRU  552  based on the RAB establishment message (step  514 ). After an RAB is established between the WTRU  552  and the eNode-B  554 , the WTRU  552  sends an RAB establishment and cell update complete message to the eNode-B  554  (step  516 ). The eNode-B  554  forwards the RAB establishment and cell update complete message to the MME/UPE  556  (step  518 ). User data is then communicated between the WTRU  552  and the MME/UPE  556  (step  520 ). 
         [0030]      FIG. 6  is a signal flow diagram of a process  600  for performing an LTE RA update in accordance with the present invention. A WTRU  652  is currently in an LTE_Idle state, and the state of the WTRU is also set to an LTE_Idle state in an MME/UPE  656  (step  602 ). In an LTE_Idle state, the WTRU  652  operates in a discontinuous reception (DRX) mode camping on a paging channel. When the WTRU  652  changes a cell, the WTRU  652  camps on a broadcast control channel (BCCH) in a new cell to receive a cell identity of the new cell and determines whether the new cell belongs to a new LTE RA (step  604 ). If it is determined that the new cell belongs to a new LTE RA, the WTRU  652  performs a RA update procedure. The LTE RA update may be performed periodically. In this operation there is no need for RAB establishment between the WTRU  652  and the eNode-B  654 , or tunnel establishment between the eNode-B  654  and the UPE  656  since there is no data traffic to transmit. 
         [0031]    The WTRU  652  transitions from an LTE_Idle state to an LTE_Active state (step  606 ). The WTRU  652  then sends an LTE RA update message to the eNode-B  654  (step  608 ). The LTE RA update message includes a temporary identity of the WTRU  652 , (e.g., RNTI). The eNode-B  654  selects a proper MME/UPE  656  based on the temporary identity of the WTRU  652  (step  610 ) and routes the LTE RA update message to the selected MME/UPE  656  (step  612 ). 
         [0032]    Upon receipt of the LTE RA update message, the MME/UPE  656  changes the state of the WTRU  652  to an LTE_Active state (step  614 ). The state of the WTRU  652  is changed because the WTRU  652  is known at the cell level at this moment and there is no need to page the WTRU  652  over the RA when new data traffic for the WTRU  652  arrives. The MME/UPE  656  then sends an LTE RA update confirm message to the eNode-B  654  (step  616 ). The LTE RA update confirm message includes a new LTE RA for the WTRU  652  and may also include an order to change the state of the WTRU  652  back to the LTE_Idle state. The eNode-B  654  forwards the LTE RA update confirm message to the WTRU (step  618 ). 
         [0033]    After receiving the LTE RA update confirm message, the WTRU  652  sends an LTE RA update complete message to the eNode-B  654  (step  620 ) and transitions to an LTE_Idle state (step  622 ). The eNode-B  654  forwards the LTE RA update complete message to the MME/UPE  656  (step  624 ). The MME/UPE  656  then changes the state of the WTRU  652  to an LTE_Idle state (step  626 ). 
         [0034]    The cell update and/or the RA update may be performed periodically. The cell update may also be performed in the case of a radio link control (RLC) unrecoverable error, upon a radio link failure, reentering service area, cell reselection, or the like. 
         [0035]    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). 
         [0036]    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. 
         [0037]    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.