Abstract:
A wireless communication method and system for performing dual mode paging over a wireless communication network having both a second-generation/third-generation (2G/3G) radio access network (RAN) and an evolved-universal mobile telecommunication system (UMTS) terrestrial radio access network (E-UTRAN). When a wireless transmit/receive unit (WTRU) registers or originates traffic with an evolved network, no additional signaling is required Otherwise, the WTRU is paged via both of the 2G/3G RAN and the E-UTRAN, depending on the response from the WTRU, data is forwarded to the WTRU via the 2G/3G RAN or the E-UTRAN.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. provisional application No. 60/763,496 filed on Jan. 30, 2006 which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF INVENTION  
       [0002]     The present invention is related to wireless communication systems. More particularly, the present invention is related to dual mode paging in a wireless communication system including a second-generation (2G)/third-generation (3G) radio access network (RAN) and an evolved-universal mobile telecommunication system (UMTS) terrestrial radio access network (E-UTRAN).  
       BACKGROUND  
       [0003]     As 3G and Long Term Evolution (LTE) technology is widely introduced, one key consideration is the need for continuing to provide service using older 2/2.5G technologies as well as 3G and LTE technologies in a seamless fashion. However, it will take some time before the geographical coverage and network capacity of 3G and LTE based networks will match that achieved by older 2/2.5G networks. Also the nature of 3G and LTE systems may mandate different footprints within the same coverage area, for example, LTE cells may be smaller than that of 3G and 2/2.5G technologies.  
         [0004]     Where 3G or LTE coverage is absent, the user will need to utilize the older 2/2.5G networks, and wireless transmit/receive units (WTRUs) operating in the networks will require the support of multiple radio access technologies (RATs), thus requiring a multi-RAT WTRU capability. Not only must the multi-RAT WTRUs be capable of searching for other types of RAT networks at power-up, but the multi-RAT WTRUs must also be capable of re-selecting the network type when moving out of the LTE coverage area.  
         [0005]     During an inter-RAT handover, the call/session must be handed over from one RAT network to another without any significant degradation of performance noticeable to the user of a dual-RAT WTRU. For general packet radio service (GPRS) capable multi-RAT WTRUs, the packet service connection must also be transferred to another network.  
         [0006]     Intersystem handover is a process of maintaining a communication connection while moving from one cell of a first RAT network to another cell of a second RAT network. As LTE networks are deployed in geographical areas overlapping older 2G/2.5G networks, seamless inter-RAT handover will become critical to providing users with uninterrupted service and reachablility. Therefore, inter-RAT handover techniques that do not affect a WTRU&#39;s performance are desired.  
       SUMMARY  
       [0007]     The present invention is related to a wireless communication method and system for performing dual mode paging for multi-mode terminal operation in that system. The wireless communication system includes an E-UTRAN, a 2G/3G RAN and at least one WTRU including an evolved element (EE) in communication with the E-UTRAN and a 2G/3G element in communication with the 2G/3G RAN. According the present invention, the WTRU shall be reachable in the LTE system while registered in 2G/3G system, and visa versa. The system may first attempt paging the WTRU over a 2G/3G RAN, and then attempt a second page on an LTE RAN. If the WTRU receives a first page message via the 2G/3G RAN, then it may respond on the 2G/3G RAN. If the WTRU did not receive the first page because it is camped on the LTE side, then it receives the second page message via the E-UTRAN. The WTRU responds to the second page message via the EE.  
         [0008]     In an alternative embodiment, it is also possible that if the WTRU camped on the 2G/3G system receives the first page, then the WTRU may access the system in page response over the EUTRAN side. The network side supporting the EUTRAN is capable of connecting to the 2G/3G network side to ensure seamless operation. Paging via the 2G/3G network side may be more robust since the 2G/3G system footprint may be more reliable than those of an LTE network. Alternatively, a global system for mobile communication (GSM) enhanced data rate for global evolution (EDGE) radio access network (GERAN) may be used instead of the 2G/3G RAN.  
         [0009]     The wireless communication system supporting EUTRAN further includes a mobility management entity (MME) and user plane entity (UPE) along with a serving general packet radio service (GPRS) support node (SGSN) that supports 2G/3G RANs. The SGSN is in communication with the MME/UPE and the 2G/3G RAN. By sending a notification via the SGSN to the WTRU, the MME/UPE is capable of supporting both first and a second page messages. In an alternative embodiment, the first page message may be generated by the SGSN while the second page message is generated by the MME/UPE based on notification received from the SGSN.  
         [0010]     The WTRU may send a response to the first page message to the MME/UPE via the 2G/3G RAN and the SGSN. The WTRU may send a response to the second page message to the MME/UPE via the E-UTRAN. In order to ensure that the WTRU is reachable via different directions, it is also possible to have other permutations of the paging procedure, (e.g., page on 2G/3G RAN response on the LTE RAN; page on the LTE RAN and response on the 2G/3G RAN).  
         [0011]     Upon changing the mode of transmission from LTE to 2G/3G radio, the WTRU may send a 2G/3G routing area (RA) update message to the 2G/3G RAN via the 2G/3G element to inform the system that it is operating in the 2G/3G mode. The 2G/3G RAN forwards the 2G/3G RA update message to the SGSN. The SGSN may update the MME/UPE by sending a 2G/3G RA update notification to MME/UPE. The SGSN update to the MME/UPE ensures that any traffic for this particular WTRU arriving at the MME/UPE shall be forwarded to the SGSN for delivery. The 2G/3G RAU is completed by updating the HSS/HLR about the current location/reachability of the WTRU. Upon successful completion, the RAU response message is sent from the SGSN to the 2G/3G RAN. The 2G/3G RAN forwards the 2G/3G RA update response message to the 2G/3G element of the WTRU.  
         [0012]     In typical operations, the WTRU may receive messages from the MME/UPE via the E-UTRAN. The WTRU may also send messages to the MME/UPE via the E-UTRAN. The WTRU may also receive messages from the MME/UPE via the SGSN and the 2G/3G RAN. The WTRU may send user data to the MME/UPE via the 2G/3G RAN and the SGSN. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     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:  
         [0014]      FIG. 1  is an exemplary block diagram of an evolved dual mode paging communication system that is configured in accordance with the present invention; and  
         [0015]      FIGS. 2A, 2B  and  2 C show signaling between the components of the system of  FIG. 1  in accordance with various embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     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.  
         [0017]     The present invention is related to a method and system for an evolution or migration of the 3GPP wireless communication system to a higher data rate, lower latency, packet-optimized communication system that supports multiple RATs.  
         [0018]      FIG. 1  is an exemplary block diagram of an evolved dual mode paging communication system  100  that is configured in accordance with the present invention. The system  100  includes at least one multi-RAT WTRU  110 , an E-UTRAN  112 , a 2G/3G RAN  114 , an SGSN  116 , am MME/UPE  118 , a home location register (HLR)/home subscriber server (HSS)  120 , a communication network  122  and an Inter access system (AS) mobility management (MM) unit  124 . The Inter AS MM  124  is a gateway function that controls the handoff between 3GPP system, (e.g. 2G/3G and LTE systems), and non-3GPP systems, (e.g. WLAN, WiMAX, 3GPP2, CDMA2000 systems)  
         [0019]     The WTRU  110  is configured for multi-mode paging according to the present invention and includes an evolved element (EE)  126  and a 2G/3G element  127 . The WTRU  110  operates in either an evolved mode or a 2G/3G mode. Typically, when the WTRU  110  operates in the evolved mode, the WTRU  110  exchanges messages with the E-UTRAN  112  via the EE  126 , and the E-UTRAN  112  exchanges messages with the MME/UPE  118 . When the WTRU  110  operates in the 2G/3G mode, the WTRU  110  exchanges messages with the 2G/3G RAN  114  via the 2G/3G element  127 , and the 2G/3G RAN  114  exchanges messages with the SGSN  116  via a Gb or Iu interface  130 . The SGSN  116  keeps track of the location of the WTRU  110  and performs security and access control functions. The SGSN  116  exchanges messages with the MME/UPE  118  regarding the location of the WTRU  110 , and its context information (e.g. security attributes, QoS profile, service profile). The connection between the SGSN  116  and MME/UPE  118  may also be used for forwarding paging messages for paging the WTRU  110  in either system; (SGSN  116  can forward paging to MME/UPE  118  to page the WTRU  110  on E-UTRAN  112 , and the MME/UPE  118  may forward a page message to SGSN  116  to page the WTRU  110  on 2G/3G RAN  114 ).  
         [0020]     Although  FIG. 1  shows the SGSN  116  serving a generic 2G/3G RAN  114 , in other embodiments the SGSN  116  may also be configured to serve a global system for mobile communication (GPRS) enhanced data rate for global evolution (EDGE) radio access network (GERAN).  
         [0021]     The MME/UPE  118  is configured to send messages, and if necessary user data, to the communication network  122  and receive messages and user data from the communication network  122 .  
         [0022]     The MME function of the MME/UPE  118  manages and stores WTRU information, such as current state, identity and user security parameters. With this WTRU information, the MME of the MME/UPE  118  also generates temporary identifiers and allocates them to WTRUs, checks for authorization of the WTRUs that may camp on particular networks, and authenticates the WTRUs.  
         [0023]     The UPE function of the MME/UPE  118  terminates, for idle state WTRUs, the downlink data path and triggers/initiates paging when downlink data arrives for the WTRU, and performs replication of the user traffic in the case of interception.  
         [0024]     The HLR/HSS  120  performs many database functions that are required in next generation mobile networks. These functions, which are well known to those of skill in the art, include the HLR, domain name servers (DNS) and the security and network access database.  
         [0025]      FIGS. 2A, 2B  and  2 C show signaling between the components of the system  100  of  FIG. 1  in accordance with various embodiments of the present invention.  
         [0026]     In the procedure  210  of  FIG. 2A , the WTRU  110  powers up in the evolved mode  211  where the EE  126  of the WTRU  110  starts by attaching to the LTE system via E-UTRAN  112  and MME/UPE  118  in accordance with the present invention. In step  212 , the EE  126  of the WTRU  110  sends an evolved-attachment (E-attachment) message indicating dual mode operation capability (i.e., that the WTRU  110  is capable of operating in both 2G/3G and LTE systems simultaneously) to the E-UTRAN  112 . In step  214 , the E-UTRAN  112  forwards the E-attachment message to the MME/UPE  118 . In step  216 , the MME/UPE  118  sends an attachment update message to the HLR/HSS  120  (step  216 ) updating the location and reachability information of the WTRU  110 . The attachment update message may include in the message header an address of the MME/UPE  118  indicating that the HSS/HLR  120  should respond to MME/UPE. In step  218 , the HLR/HSS  120  accepts the attachment update and sends an attachment accept message to the MME of the MME/UPE  118 . In step  220 , the MME/UPE  118  performs IP configuration procedures with the access stratum to allocate an IP address to the WTRU  110 . Then the MME/UPE  118  sends an attachment accept message that includes the assigned IP address for the WTRU  110 , a packet-temporary mobile subscriber identity (P-TMSI), an evolved-routing area (E-RA) and a 2G/3G RA), to the E-UTRAN  112 . In step  222 , the E-UTRAN  112  forwards the attachment accept message to the EE  126  of the WTRU  110 . In step  224 , a communication path is established between the SGSN  116 , where the MME/UPE  118  establishes the state of the WTRU  110  as being registered in MME/UPE  118 .  
         [0027]     In procedure  230  of  FIG. 2A , a service request  231  is performed, in which a user data path is established between the EE  126  of the WTRU  110  and the MME/UPE  118  in accordance with the present invention. In step  232 , the WTRU  110  sends a radio access bearer (RAB) establishment request message, (including a service ID (identifying the service being requested in the service request  231 ), quality of service (QoS) data, and a P-TMSI), to the E-UTRAN  112  (step  232 ). In step  234 , the E-UTRAN  112  sends a user plane bearer establishment request message, (including the service ID, the QoS data and the P-TMSI), to the MME/UPE  118 . In step  236 , the MME/UPE  118  responds by establishing the direct tunnel between the AS (not pictured) and the EUTRAN  112  and upon successful completion the MME/UPE  118  sends a user plane bearer establishment accept message, (including a service ID, QoS data) to the E-UTRAN  112 . In step  238 , the E-UTRAN  112  sends a RAB establishment accept message, (including a channel number, bandwidth and QoS data), to the EE  126  of the WTRU  110 . In step  240 , a user data path is established between the EE  126  of the WTRU  110  and the MME/UPE  118  such that data can be exchanged using the established path. The WTRU  110  returns to an idle mode on the E-UTRAN  112  after successfully attaching to the system if there is no data to send or receive.  
         [0028]     In the procedure  250  of  FIG. 2B , dual pages are received after the WTRU switches to the 2G/3G mode in accordance with the present invention. The 2G/3G element  127  of the WTRU  110  may switch to 2G/3G mode of operation for multiple reasons such as, better radio environment, or performing CS call. In step  252 , the WTRU  110  detects the 2G/3G new routing area (RA) information and starts new RA update procedures by sending a 2G/3G RA update message to the 2G/3G RAN  114 , which then forwards the 2G/3G RA update message to the SGSN  116 . The SGSN then updates the HLR/HSS  120  with the new location and reachability of the WTRU  110  and establish the necessary state machine associated with this mode of operation. The SGSN  116  also detects that this is multimode WTRU  110  that has contacts in the LTE system. Upon successful operation, in step  254 , the SGSN  116  sends a 2G/3G RA update response message to the 2G/3G RAN  114 , which then forwards the 2G/3G RA update response message to the 2G/3G element  127  of the WTRU  110 . In step  256 , the SGSN  116  may exchange 2G/3G RA update messages with the MME/UPE  118  to maintain the current state of the WTRU. In step  258 , a user data path is established between the communication network  122  and the MME/UPE  118 . Upon reception of data to be delivered to the WTRU, in step  260 , the MME/UPE  118  sends a first page message to the 2G/3G element  127  of the WTRU  110  via the SGSN  16  and the 2G/3G RAN  114 . In step  262 , the MME/UPE  118  then sends a second page message to the EE  126  of the WTRU  110  via the E-UTRAN  112 . In step  264 , the 2G/3G element  127  of the WTRU  110  sends a 2G/3G page response message to the MME/UPE  118  via the 2G/3G RAN  114  and the SGSN  116 .  
         [0029]     In procedure  266  of  FIG. 2C , RABs are established and data traffic is redirected to facilitate the exchange of user data to and from the 2G/3G element  127  of the WTRU  110 . In step  268 , RABs are established between the 2G/3G element  127  of the WTRU  110  and the 2G/3G RAN  114 . In step  270 , bearer establishment signaling is exchanged between the 2G/3G RAN  114  and the SGSN  116 . In step  272 , the MME/UPE  118  redirects traffic to the 2G/3G path. In step  274 , user data is sent from the MME/UPE  118  to the 2G/3G element  127  of the WTRU  110  via the SGSN  116  and the 2G/3G RAN  114 . In step  276 , user data is sent back from the 2G/3G element  127  of the WTRU  110  to the MME/UPE  118  via the 2G/3G RAN  114  and the SGSN  116 . In step  278 , a user data path is established between the MME/UPE  118  and the communication network  122 .  
         [0030]     The procedure  280  of  FIG. 2C  is an alternative to the procedure  266  to facilitate the exchange of user data to and from the EE  126  of the WTRU  110 . In step  282 , the MME/UPE  118  signals the 2G/3G element  127  of the WTRU  110  via the SGSN  116  and the 2G/3G RAN  114  to re-direct the user such that the WTRU  110  returns to idle on the E-UTRAN  112 . In step  284 , the EE  126  of the WTRU  110  sends a RAB establish message to the E-UTRAN  112 . In step  286 , the E-UTRAN  112  responds by sending a RAB established message to the EE  126  of the WTRU  110 . In step  288 , the E-UTRAN  112  sends a RAB established message to the MME/UPE  288 . In step  290 , the EE  126  of the WTRU  110  sends a page response message to the E-UTRAN  112 , which forwards the page response message to the MME/UPE  118 . In step  292 , user data is sent from the MME/UPE  118  to the E-UTRAN  112 , which forwards the user data to the EE  126  of the WTRU  110 . In step  294 , the EE  126  of the WTRU  110  sends user data back to the E-UTRAN  112 , which forwards the user data to the MME/UPE  118 . In step  296 , the MME/UPE  118  establishes a user data path with the communication network  122 .  
         [0031]     The present invention may be implemented in the network layer (layer  3 ), transport layer, and/or the session layer of a 3G wireless communication system. The present invention applies to wideband code division multiple access (WCDMA) frequency division duplex (FDD) wireless communication systems.  
         [0032]     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).  
         [0033]     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.  
         [0034]     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.