Abstract:
A method and an apparatus for operating a timer in a wireless transmit receive unit (WTRU) are described. In one scenario, the method includes the WTRU receiving a circuit switched (CS) call request and a CS service notification, transmitting an evolved packet system mobility management service request (ESR) message, starting the timer, and stopping the timer upon reception of a handover command or a cell change command to indicate a successful CS fallback procedure. In another scenario, the method includes the WTRU receiving a CS call request and a CS service notification, transmitting an ESR message including a CS call rejection indication, starting the timer, and stopping the timer upon reception of an acknowledgement that the ESR message was transmitted or received to indicate a successful CS fallback procedure.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Nos. 61/112,880, filed Nov. 10, 2008 and 61/166,071, filed Apr. 2, 2009, which are incorporated by reference as if fully set forth herein. 
    
    
     FIELD OF INVENTION 
     This application is related to wireless communications. 
     BACKGROUND 
       FIG. 1  shows an overview of an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)  100  in accordance with the prior art. As shown in  FIG. 1 , the E-UTRAN  100  includes three Evolved Node-Bs (eNBs)  102 . However, any number of eNBs  102  may be included in the E-UTRAN  100 . The eNBs  102  are interconnected by an X2 interface  108 . The eNBs  102  are also connected by an S1 interface  106  to an Evolved Packet Core (EPC)  104 . The EPC  104  includes a Mobility Management Entity (MME)  112  and a Serving Gateway (S-GW)  110 . 
       FIG. 2  is a flow diagram of an Evolved Packet System (EPS) Mobility Management (EMM) Service Request (ESR) procedure  200  in accordance with the prior art. At step  202 , a wireless transmit receive unit (WTRU) transmits an ESR message to an eNB. At step  204 , the WTRU starts a timer, such as timer T3417ext, for example. At step  206 , the WTRU enters an EMM-SERVICE-REQUEST-INITIATED state. At step  208 , the WTRU determines that a user plane radio bearer is set up and therefore the ESR procedure  200  is successful. At step  210 , the WTRU stops the timer and enters an EMM-REGISTERED state. 
       FIG. 3  is a signal diagram of an ESR procedure  300  in accordance with the prior art. An eNB  302  transmits a circuit switched (CS) call request  304  to a WTRU  306 . The eNB  302  also transmits a CS service notification  308  to the WTRU  306 . The WTRU  306  responds to the eNB  302  with an ESR message  310 . The WTRU  306  then starts a timer  312 . If the Non-Access Stratum (NAS) security mode control procedure is completed  314 , or if NAS radio bearers are established  316  or a service reject message  318  is received by the WTRU  306 , the timer is stopped  320 . 
     If the WTRU  306  is in an EMM-CONNECTED mode when the ESR  310  is transmitted to the network, NAS security  314  may already be established. Furthermore, if the WTRU  306  receives a change cell message or a handover command, no bearers are setup. Consequently, other than receiving a service reject message, which indicates a failure of the ESR procedure  300 , the WTRU  306  will not stop the timer even though the ESR procedure  300  was successful. 
     In addition, if the WTRU  306  is in EMM-IDLE mode and transmits the ESR message  310  to the eNB  302  for a CS fallback request, the network may not initiate the security mode procedure. The security mode procedure is a network operator option and may not be implemented by all operators. In this instance, the WTRU  306  may not use the completion of the security mode procedure as an indication to stop the timer, and the timer may continue to run. 
     The foregoing discussion with respect to LTE is provided as an example and may have applicability to other wireless technologies and standards. Furthermore, while the foregoing discussion is with respect to a timer, one skilled in the art may recognize that any time keeping or control device, such as a counter, may be used in place of the timer. 
     SUMMARY 
     A method and an apparatus is are disclosed for operating a timer in a WTRU. The WTRU may be in a connected mode. The receiver of the WTRU may be configured to receive a CS call request. The transmitter of the WTRU may be configured to transmit an ESR message in response to the CS call request. The WTRU may be configured to start a timer in response to the transmittal of the ESR message. The receiver of the WTRU may be configured to receive a handover command in response to the transmittal of the ESR, and the WTRU may be configured to stop the timer upon reception of the handover command. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more detailed understanding may be had from the following description, given by way of example in conjunction with the accompanying drawings wherein: 
         FIG. 1  shows an overview of an Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) in accordance with the prior art; 
         FIG. 2  is a flow diagram of an ESR procedure in accordance with the prior art; 
         FIG. 3  is a signal diagram of an ESR procedure in accordance with the prior art; 
         FIG. 4  shows a wireless communication system in accordance with an embodiment; 
         FIG. 5  is a functional block diagram of the WTRU and the eNB of the wireless communication system of  FIG. 4 ; 
         FIG. 6  shows a signaling diagram of an ESR procedure in accordance with an embodiment; 
         FIG. 7A  is a signal diagram showing a method to operate a timer in accordance with an embodiment; and 
         FIG. 7B  is a signal diagram showing a method to operate the timer in accordance with another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
       FIG. 4  shows a wireless communication system  400  in accordance with an embodiment. The communication system  400  includes a plurality of WTRUs  410  and an e Node B (eNB)  420 . As shown in  FIG. 4 , the WTRUs  410 , are in communication with the eNB  420 . Although three WTRUs  410  and one eNB  420  are shown in  FIG. 4 , it should be noted that any combination of wireless and wired devices may be included in the wireless communication system  400 . 
     Each of the WTRUs  410  may include an EMM entity  413 . The WTRUs  410  may operate in one of two mobility states. When at least one of the WTRUs  410  has no NAS signaling connection between the WTRUs  410  and the eNB  420 , it may be in an EMM-IDLE mode. When one of the WTRUs  410  establishes an NAS signaling connection, it is in an EMM-CONNECTED mode. 
     Each of the WTRUs  410  may use a service request procedure to transfer their EMM mode from EMM-IDLE to EMM-CONNECTED and to establish radio bearers to send uplink (UL) user data. UL data is data that is sent from the WTRUs  410  to the eNB  420 . 
     The service request procedure may also be used to invoke a mobile originating (MO) or mobile terminating (MT) CS fallback procedure. The procedure may also be used when the network has downlink (DL) signaling pending, one of the WTRUs  410  has UL signaling pending, one of the WTRUs  410  or the eNB  420  has user data pending and the WTRU for which the user data is intended is in EMM-IDLE mode, or when one of the WTRUs  410  is in EMM-IDLE or EMM-CONNECTED mode and has requested to perform MO or MT CS fallback. 
     The service request procedure may be initiated by at least one of the WTRUs  410 . However, for DL signaling or transfer of user data while a WTRU is in EMM-IDLE mode, a trigger may be sent by the eNB  420  in a paging message. The WTRU targeted by the paging message may invoke the service request procedure when the WTRU receives the paging message, has pending user data to be sent, or has pending UL signaling. A WTRU in EMM-IDLE or EMM-CONNECTED mode may invoke the service request procedure when the WTRU receives a CS fallback request or receives a notification for a CS call, such as a page or a service notification. 
       FIG. 5  is a functional block diagram  500  of one of the WTRUs  410  and the eNB  420  of the wireless communication system  400  of  FIG. 4 . As shown in  FIG. 5 , the WTRU  410  is in communication with the eNB  420 . In addition to the components that may be found in a typical WTRU, the WTRU  410  includes a processor  515 , a receiver  516 , a transmitter  517 , and an antenna  518 . The WTRU  410  may also include a user interface  521 , which may include, but is not limited to, an LCD or LED screen, a touch screen, a keyboard, a stylus, or any other typical input/output device. The WTRU  410  may also include memory  519 , both volatile and non-volatile as well as interfaces  520  to other WTRU&#39;s, such as USB ports, serial ports and the like. The WTRU  410  may also include a control device, such as a timer, a counter or other time or count based control devices. The control device may be electrically coupled to the processor  515 . 
     The receiver  516  and the transmitter  517  are in communication with the processor  515 . The antenna  518  is in communication with both the receiver  516  and the transmitter  517  to facilitate the transmission and reception of wireless data. The WTRU  410  may be configured with a non-access stratum entity (NAS), a radio resource control entity (RRC), a medium access control entity (MAC) and other entities that serve to process particular commands and perform particular duties. The WTRU  410  may be configured to operate in a packet switched (PS) and/or a CS environment, and to receive, transmit and process both PS and CS commands. The WTRU  410  may include counters, timers, and other devices used for timing various procedures. 
     In addition to the components that may be found in a typical eNB, the eNB  420  includes a processor  525 , a receiver  526 , a transmitter  527 , and an antenna  528 . The receiver  526  and the transmitter  527  are in communication with the processor  525 . The antenna  528  is in communication with both the receiver  526  and the transmitter  527  to facilitate the transmission and reception of wireless data. 
       FIG. 6  shows a signaling diagram of an ESR procedure  600  in accordance with an embodiment. An eNB  602  transmits a CS call request  606  and a CS service notification  608  to a WTRU  604 . The WTRU  604 , which is in connected mode, transmits an extended service request  610  to the eNB  602 . The WTRU starts a timer  612 . The WTRU  604  receives a handover or cell change command  614  and the WTRU stops the timer  616 . Therefore, along with the other criteria for stopping the timer, as shown in  FIG. 6 , the WTRU  604  stops the timer  616  when it receives a handover or cell change command  614 . If the timer expires prior to a mobility message being received by the WTRU  604 , such as a handover command or cell change command, the procedure is aborted. 
     When a WTRU transmits an ESR for a CS fallback and the request is rejected, the WTRU may send an indication to the eNB, in the extended service request, that the CS call is rejected. If this occurs, a trigger may be used to stop the timer.  FIG. 7A  is a signal diagram showing a method to stop a timer  700  when an ESR message is sent with an indication of call rejection in accordance with an embodiment. An eNB  702  sends a CS call request  706  and a CS service notification  708  to a WTRU  704 . The WTRU  704  sends an ESR message including a CS call rejection indication  710  to the eNB  702 . The timer is started  712  once the ESR message with the CS call rejection indication  710  is transmitted. The timer is then stopped  714 . The timer may be stopped  714  immediately after the ESR message  710  is transmitted. Alternatively, the timer may be stopped after a predetermined time has elapsed, for example, after half the time that the timer would have run if the CS call was accepted. The NAS entity may receive a notification from a lower layer entity, such as the RRC or MAC, for example, that acknowledges the transmittal of the ESR message  710 . The notification may be used as a trigger to stop the timer. 
       FIG. 7B  is a signal diagram showing a method to stop a timer  750  when an ESR message is sent with an indication of call rejection in accordance with another embodiment. The eNB  702  sends the CS call request  706  and the CS service notification  708  to the WTRU  704 . The WTRU  704  sends the ESR message including a CS call rejection indication  710  to the eNB  702 . A protocol data unit (PDU)  752 , a NAS message  754 , such as a NAS message sent from the eNB  702  to the WTRU  704  to acknowledge receipt of the ESR message  710 , or an RRC message  756 , is sent from or to the WTRU  704 . The receipt or transmission of the message triggers the WTRU  704  to stop the timer  714 . 
     Alternatively, the timer may be allowed to expire without the WTRU  704  determining that the expiration of the timer indicates a problem. Furthermore, the timer may not be started at all if the CS call is rejected. The stopping of the timer indicates the fallback procedure was completed successfully. 
     The present disclosure, while directed to a timer, may be applicable to any number of control devices, such as counters, for example. A timer, as used in herein, is an example of a control device. 
     Although features and elements are described above in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. The methods or flow charts provided herein may be implemented in a computer program, software, or firmware incorporated 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). 
     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. 
     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) or Ultra Wide Band (UWB) module.