Abstract:
The present invention discloses a method, system and device for processing circuit switched (CS) services in an evolved packet network. The method includes: by a mobility management entity (MME), receiving a mobile terminated (MT) service indication from a mobile switching center (MSC); sending the MT service indication to user equipment (UE); and receiving an MT service response returned by the UE and performing subsequent operations according to the MT service response. In the method of the present invention, when an MT service arrives, the MME does not trigger the evolved NodeB (eNodeB) to hand over the packet switched (PS) services of the UE but notifies the UE of the MT service and performs subsequent operations according to the MT service response returned by the UE, thus avoiding the waste of network resources caused by a meaningless handover of PS services.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Application No. PCT/CN2008/073200, filed on Nov. 26, 2008, which claims priority to Chinese Patent Application No. 200810002762.X, filed on Jan. 16, 2008, both of which are hereby incorporated by reference in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to communications technologies, and in particular, to a method, system and device for processing circuit switched services in an evolved packet network. 
       BACKGROUND OF THE INVENTION 
       [0003]    To answer the challenge of wireless broadband technologies and maintain the leadership of the 3 rd  Generation Partnership Project (3GPP) networks, the 3GPP organization prepared a long term evolution (LTE) plan at the end of 2004. Directed by the LTE plan, new mobile communications network architecture is defined, where only the packet switched (PS) domain remains. The architecture is called an evolved packet system (EPS). 
         [0004]    To enable circuit switched (CS) services in an EPS network, a prior art provides a method for processing CS services in an EPS network, which may be described as a CS fallback method. 
         [0005]    When a mobile switching center (MSC) receives a mobile terminated (MT) service, such as a CS voice call, the MSC sends a page message to a mobility management entity (MME) and the MME pages user equipment (UE) via the EPS network. When an evolved NodeB (eNodeB) receives the page message, the eNodeB first executes a PS service handover, that is, the eNodeB hands over the ongoing PS service of the UE to the PS domain of a general packet radio service/universal mobile telecommunications system (GPRS/UMTS) network. Then, the eNodeB hands over the UE to a 2 nd  generation/3 rd  generation (2G/3G) network, that is, the UE chooses a 2G/3G cell to camp. When the UE returns a page response to the MGC in the GPRS/UMTS network, the eNodeB completes processing of the MT service. 
         [0006]    During research and practice of the prior art, however, the inventor finds that the prior art has at least the following weaknesses: 
         [0007]    By using the CS fallback method in the prior art, the eNodeB executes a PS service handover immediately when receiving the page message from the MME, which results in the following problems: 
         [0008]    1. Waste of network resources. According to the prior art, when an MT service arrives, the eNodeB hands over the PS service to the PS domain of a 2G/3G network and connects the MT service. In practice, the following case often happens: When the UE is handed over to a 2G/3G network and an MT service is connected, the user rejects the MT service because the user is unwilling or unable to answer. The eNodeB regards such MT services as services that have been completed and the eNodeB then hands over the PS services of the UE to the EPS network. Two PS service handovers are performed for an MT service that is not normally executed, and therefore network resources are wasted. 
         [0009]    2. Impact on the ongoing PS service of the UE. For example, a UE is in a PS service (such as a video conference) in an EPS network when it receives a CS MT service (such as a private call). According to the prior art, the eNodeB hands over the video conference to the PS domain a 2G/3G network, but because the PS domain of the 2G/3G network does not support certain PS services in the EPS network, such as the video conference, the PS service will fail. Thus, the prior art impacts the ongoing PS services. 
       SUMMARY OF THE INVENTION 
       [0010]    Embodiments of the present invention provide a method, system and device for processing CS services in an evolved packet network so as to avoid the waste of network resources and not to impact the current PS services of a UE. 
         [0011]    For the above purpose, the embodiments of the present invention are implemented via the following technical solution: 
         [0012]    A method for processing CS services in an evolved packet network includes: 
         [0013]    receiving, by an MME, an MT service indication from an MSC; 
         [0014]    sending, by the MME, the MT service indication to a UE; and 
         [0015]    by the MME, receiving an MT service response returned by the UE and performing subsequent operations according to the MT service response. 
         [0016]    A method for processing CS services in an evolved packet network includes: 
         [0017]    receiving, by an MME, a short message from an MSC; 
         [0018]    by the MME, sending the short message to a UE if the UE is in active mode and activating the UE and sending the short message to the UE if the UE is in idle mode; and 
         [0019]    receiving, by the MME, a short message response from the UE. 
         [0020]    An MME includes: 
         [0021]    a page message receiving unit, configured to receive an MT service indication from an MSC; 
         [0022]    an MT service notifying unit, configured to send the MT service indication to a UE; 
         [0023]    a response receiving unit, configured to receive an MT service response returned by the UE; and 
         [0024]    a response processing unit, configured to perform subsequent operations according to the MT service response. 
         [0025]    An MME includes: 
         [0026]    a receiving unit, configured to receive a short message from an MSC; 
         [0027]    a state judging unit, configured to judge whether a UE is in active or idle mode; 
         [0028]    a sending unit, configured to send the short message received by the receiving unit to the UE when the state judging unit determines that the UE is in active mode; 
         [0029]    an activating and sending unit, configured to activate the UE when the state judging unit determines that the UE is in idle mode and send the short message received by the receiving unit to the activated UE; and 
         [0030]    a short message response receiving unit, configured to receive a short message response from the UE. 
         [0031]    A UE includes: 
         [0032]    a notification receiving unit, configured to receive an MT service indication sent by an MME; 
         [0033]    an notifying unit, configured to notify the user of the MT service after the notification receiving unit receives the MT service indication; and 
         [0034]    a response sending unit, configured to return an MT service response to the MME according to a choice of the user regarding the MT service. 
         [0035]    A system for processing CS services in an evolved packet network includes an MSC and an MME, where: 
         [0036]    the MSC includes a service indication sending unit, configured to send an MT service indication to the MME after receiving the MT service indication; 
         [0037]    the MME includes: 
         [0038]    a page message receiving unit, configured to receive the MT service indication from the MSC; 
         [0039]    an MT service notifying unit, configured to send the MT service indication to a UE; 
         [0040]    a response receiving unit, configured to receive an MT service response returned by the UE; and 
         [0041]    a response processing unit, configured to perform subsequent operations according to the MT service response. 
         [0042]    The technical solution provides the following benefits: 
         [0043]    In the embodiments of the present invention, when a CS MT service arrives, the MME sends an MT service indication to notify the UE of the MT service and then performs subsequent operations according to an MT service response received from the UE. When the MT service arrives, the MME does not trigger the eNodeB to hand over the PS service of the UE, but notifies the UE of the MT service and carries out subsequent processing according to the MT service response returned by the UE. Thus, the embodiments of the present invention avoid the waste of network resources caused by a meaningless PS service handover and do not impact the ongoing PS services of the UE. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]      FIG. 1  is a flowchart of a CS fallback method provided in an embodiment of the present invention; 
           [0045]      FIG. 2  is a signaling flow of a CS fallback method provided in Embodiment 1 of the present invention; 
           [0046]      FIG. 3  is a signaling flow where a UE is activated and notified of an incoming MT service in Embodiment 1 of the present invention; 
           [0047]      FIG. 4  is a signaling flow of a CS fallback method provided in Embodiment 2 of the present invention; 
           [0048]      FIG. 5  is a signaling flow where a UE is activated and notified of an incoming MT service in Embodiment 2 of the present invention; 
           [0049]      FIG. 6  is a signaling flow of an MT service restoring method provided in an embodiment of the present invention; and 
           [0050]      FIG. 7  shows a structure of a CS fallback system provided in an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0051]    To better explain the purpose, technical solution and advantages of the present invention, the embodiments of the present invention are hereinafter described in detail with reference to the accompanying drawings. 
         [0052]    When a CS MT service arrives, as shown in  FIG. 1 , a CS fallback method provided in an embodiment of the present invention includes: 
         [0053]    Step  101 : An MME receives an MT service indication from an MSC. 
         [0054]    Step  102 : The MME forwards the MT service indication to a UE. 
         [0055]    The MT service indication notifies the UE of an MT service. 
         [0056]    Step  103 : The MME receives an MT service response from the UE. 
         [0057]    Step  104 : The MME carries out subsequent processing according to the MT service response. 
         [0058]    The above is a CS fallback method provided in an embodiment of the present invention. In the embodiment, when a CS MT service arrives, the MME first sends an MT service indication to notify the UE of the MT service and after reception of the MT service response from the UE, the MME carries out subsequent processing according to the MT service response. In the method provided in the embodiment of the present invention, when an MT service arrives, the MME does not trigger the eNodeB to hand over the PS service of the UE, but notifies the UE of the MT service and carries out subsequent processing according to the MT service response returned by the UE. Thus, the method avoids the waste of network resources caused by a meaningless PS service handover and does not impact the ongoing PS service of the UE. 
         [0059]    In a specific implementation of the embodiment of the present invention, the MT service response may carry a user choice result. If the use chooses to reject the MT service, the MME returns an MT service Reject message to the MSC when the MME carries out subsequent processing according to the MT service response. 
         [0060]    If the user chooses to accept the MT service, the MME sends a PS service handover request to the eNodeB and the eNodeB executes a PS service handover when the eNodeB receives the handover request and hands the UE over to a 2G/3G network. After the UE is handed over to the 2G/3G network, the eNodeB sends a first page response to the MSC and completes MT service processing. 
         [0061]    In another embodiment of the present invention, if the user chooses to accept the MT service, the MME does not hand over the current PS service of the UE according to a configured network operation policy and therefore, the MME does not need to send a PS service handover request to the eNodeB and the eNodeB does not need to execute a PS handover later. In this case, after the UE sends the response indicating acceptance of the MT service, or receives a response from the MME regarding the UE&#39;s acceptance of the MT service, the UE accesses the 2G/3G network directly to complete the MT service processing. 
         [0062]    The above describes the CS fallback method provided in an embodiment of the present invention. The following describes specific signaling flows of the method. 
         [0063]    As shown in  FIG. 2 , a signaling flow of the CS fallback method in Embodiment 1 of the present invention includes: 
         [0064]    Step  201 : The MSC receives an MT service indication and sends a first page message to the MME. 
         [0065]    In practice, the first page message may carry an international mobile subscriber identity (IMSI) of the UE. 
         [0066]    Step  202 : When receiving the first page message, the MME queries the UE state. If the UE is in idle mode, the MME sends a second page message to the eNodeB. If the UE is in active mode, the process proceeds to step  205 . 
         [0067]    In practice, the first page message may carry the MT service indication sent by the MSC to the MME. Therefore, the first page message may be named MT service request or alike. In addition, if the first page message carries the MT service indication, in step  302 , after the MME receives the first page message, the MME needs to parse the first page message and query the UE state after the MT service indication is obtained. 
         [0068]    In addition, the first page message may not carry the MT service indication. In this case, the MME is set to query the UE state once it receives the first page message. In this case, the first page message is equivalent to an MT service indication. 
         [0069]    Step  203 : The eNodeB broadcasts the second page message in the cell it manages. 
         [0070]    Step  204 : The UE receives the second page message and returns a service request to the MME. 
         [0071]    The MME sends the second page message via the eNodeB to activate the idle UE. 
         [0072]    Step  205 : After receiving of the service request, the MME sends an MT service indication to the UE. The MT service indication is intended to notify the UE of the MT service. 
         [0073]    The MT service indication shown in  FIG. 2  is a non access stratum (NAS) message and therefore it may be sent to the UE directly from the MME. In another embodiment of the present invention, the MT service indication is an access stratum message (such as Page). The access stratum message may carry the MT service indication and is sent by the MME to the eNodeB and forwarded by the eNodeB to the UE. This does not impact the implementation of the present invention. 
         [0074]    Step  206 : After the UE receives the MT service indication, the UE notifies the user of the MT service. 
         [0075]    In practice, the UE notifies the user of the MT service according to the presetting of the user. For example, the UE may ring, or vibrate, or ring and vibrate, or give a text notify, to notify the user of the MT service. 
         [0076]    After the user makes a choice regarding the MT service, the UE executes step  207 . 
         [0077]    Step  207 : The UE sends an MT service response to the MME. 
         [0078]    The MT service response may carry the user choice result (accept or reject) or the MT service response does not carry a user choice result, that is, the user choice result is null. If the MT service response does not carry a user choice result, the MME may decide the user choice according to default settings. A common scenario is that, if the MT service response does not carry the choice result, the MME thinks that the user accepts the MT service by default. 
         [0079]    Step  208 : The MME obtains the choice result carried in the MT service response. If the user chooses to reject the MT service, the MME sends a first page reject message (the foregoing MT service reject). If the user chooses to accept the MT service, the process proceeds to step  209 . 
         [0080]    If the UE rejects the MT service, it is unnecessary to execute the MT service and the MME returns a first page reject message to the MSC to end the MT service. In the method provided in the embodiment of the present invention, if the UE does not execute the MT service, the eNodeB does not hand over the PS service of the UE. Thus the method avoids the waste of network resources caused by a meaningless PS handover and will not impact the current PS service of the UE. 
         [0081]    The first page reject message may carry a cause value indicating the reason for rejecting the MT service or the message may not carry the cause value. Whether the message carries the cause value does not impact the implementation of the present invention. 
         [0082]    In addition, the case often happens in daily life that the user does not see or feel the notifying of the UE in a long time. To improve the work efficiency of the MME, it may be defined in advance that, if the MME does not receive the MT service response from the UE within a preset time T, the MME thinks that the user rejects the MT service. And in this case, the MME sends the first page reject message to the MSC to reject the MT service. 
         [0083]    Step  209 : The MME sends a PS service handover request to the eNodeB. 
         [0084]    Step  210 : The eNodeB receives the PS service handover request and initiates a PS service handover procedure to hand the UE over to the 2G/3G network. 
         [0085]    Step  211 : After the UE is handed over to the 2G/3G network, the UE sends a first page response and completes the MT service processing. 
         [0086]    In another embodiment of the present invention, after the MME receives the first page message, the MME may not query the UE state but thinks the UE is in idle mode by default. Then, the MME sends a second page message and an MT service indication to the UE to notify the active or idle UE of the MT service. 
         [0087]    The above is a signaling flow provided in Embodiment 1 of the present invention. When the MME receives the first page message sent by the MSC in step  201 , the MME may notify an idle or active UE of the MT service via steps  202 - 205  in Embodiment 1 of the present invention or via the signaling flow shown in  FIG. 3 . The signaling flow includes: 
         [0088]    Step  301 : The MME receives a first page message from the MSC and sends a third page message to the eNodeB. The third page message carries at least an MT service indication. 
         [0089]    In practice, the MT service indication may be a page cause value in the third page message or an independent information element in the third page message, which will not impact the implementation of the present invention. 
         [0090]    Step  302 : The eNodeB broadcasts the third page message in the cell it manages. 
         [0091]    Step  303 : After the UE receives the third page message, the UE notifies the user of the MT service. 
         [0092]    The signaling flow shown in  FIG. 3  is different from steps  202 - 205  in Embodiment 1 of the present invention in the following aspects: 
         [0093]    In Embodiment 1 of the present invention, the MME sends a message to notify the UE of an MT service only when the UE is in active mode. The UE may be already in active mode when the MME receives the first page message, or the UE may be activated through paging by the MME. In the signaling flow shown in  FIG. 3 , however, the MME does not check whether the UE is in active mode but notifies the UE of an MT service directly via a third page message. 
         [0094]    Specifically, in Embodiment 1 of the present invention, when the UE is in idle mode, the MME sends the second page message and the MT service indication to notify the UE of the MT service; when the UE is in active mode, the MME sends the MT service indication directly to notify the UE of the MT service. The benefit of this signaling flow is that it does not impact the paging mechanism in the existing EPS network. 
         [0095]    In the signaling flow shown in  FIG. 3 , the MME sends a third page message that carries the MT service indication to notify the UE of the MT service. The benefit is that it increases the processing efficiency of the MME and reduces the call delay. 
         [0096]    To let the UE know information of the MT service originator to help the user make a choice regarding the MT service, in the preceding and following embodiments of the present invention, the first page message sent by the MSC to the MME may further carry MT service related information. 
         [0097]    The MT service related information includes: a mobile station ISDN (MSISDN) of the originator, or a service type indication, such as short message service (SMS), location service (LCS), and unstructured supplementary service data (USSD). In addition, to help the MSC determine the MT service associated with the received MT service response, the MT service related information may further include an MT service ID that is allocated by the MSC or an existing ID (like a call number). 
         [0098]    Because the first page message sent by the MSC to the MME carries the MT service related information, the page message or MT service indication sent by the MME to the UE may further carry the MT service related information. In this case, the UE notifies the user of the MT service according to the received MT service related information according to the presetting of the user. For example, the UE may display the MSISDN of the originator to the user or notify the user of the service type. 
         [0099]    In the foregoing method, the user may choose to accept or reject the service. In certain scenarios, however, the user wishes to process the MT service after waiting for some time. It is therefore necessary to hold the MT service. Embodiment 2 of the present invention provides another CS fallback method. The method includes the following step based on the method shown in  FIG. 1 : 
         [0100]    If the user chooses to hold the MT service, the MME sends an MT service Hold message to the MSC. 
         [0101]    In addition, to guarantee that the MT service is restorable, the method further includes: 
         [0102]    If the UE requests restoration of the held MT service, the MME notifies the MSC to restore the MT service; the MSC judges whether the MT service can be restored and if the service can be restored, the MSC notifies the UE of accessing the 2G/3G network via the MME and the UE then completes the MT service, or the MME triggers the eNodeB to hand the UE over to the 2G/3G network to complete the MT service according to a configured operation policy. If the MSC cannot restore the MT service, the restoration procedure is ended. 
         [0103]      FIG. 4  shows a signaling flow of the CS fallback method in Embodiment 2 of the present invention. The signaling flow allows the user to choose to hold the MT service. The signaling flow includes: 
         [0104]    Step  401 : The MSC receives an MT service request and sends a first page message to the MME. 
         [0105]    To avoid long-term MT service holding that consumes system resources, the method may further include a step of presetting a call hold timer and the first page message further carries the call hold timer length. 
         [0106]    Step  402 : The MME queries the state of the UE associated with the IMSI. If the UE is in idle mode, the MME sends a fourth page message to the eNodeB. If the UE is in active mode, the process proceeds to step  405 . 
         [0107]    Step  403 : The eNodeB broadcasts the fourth page message in the cell it manages. 
         [0108]    Step  404 : The UE receives the fourth page message and returns a service request to the MME, 
         [0109]    Step  405 : The MME sends an MT service indication to the UE to notify the UE of an MT service. 
         [0110]    The ME service indication may or may not carry the MT service related information and/or the call hold timer length, which does not impact the implementation of the present invention. 
         [0111]    Step  406 : After the UE receives the MT service indication, the UE notifies the user of the MT service. 
         [0112]    In practice, if the MT service indication carries the MT service related information, the UE notifies the user of the MT service according to the received MT service related information according to the presetting of the user. For example, the UE may display the MSISDN of the originator to the user or notify the user of the service type. The UE may ring, or vibrate, or ring and vibrate, or give a text notify to notify the user of the MT service. 
         [0113]    After the user makes a choice regarding the MT service, the UE executes step  407 . 
         [0114]    Step  407 : The UE sends an MT service response to the MME. 
         [0115]    The MT service response may carry the user choice result (accept or reject) or the MT service response does not carry a user choice result, that is, the user choice result is null. If the MT service response does not carry a user choice result, the MME may decide the user choice according to default settings. A common scenario is that, if the MT service response does not carry the choice result, the MME thinks that the user accepts the MT service by default. 
         [0116]    If the user chooses to hold the service, the UE starts the associated timer according to the call hold timer length. 
         [0117]    Step  408 : The MME obtains the choice result carried in the MT service response. If the user chooses to hold the MT service, the MME sends an MT service Hold message to the MSC; if the user chooses to reject or accept the MT service, the subsequent steps are the same as the procedure provided in Embodiment 1 of the present invention. 
         [0118]    Step  409 : The MSC starts the associated timer according to the preset call hold timer length. 
         [0119]    In another embodiment of the present invention, after the MME receives the first page message, the MME may not query the UE state but thinks the UE is in idle mode by default. Then, the MME sends the fourth page message and the MT service indication to the UE to notify the active or idle UE of the MT service. 
         [0120]    The above is a specific signaling flow of the CS fallback method provided in Embodiment 2 of the present invention. The active or idle UE may be notified of the MT service via steps  402 - 405 . In another embodiment of the present invention, the signaling flow shown in  FIG. 5  may be adopted to notify an active or idle UE of an MT service. The signaling flow includes: 
         [0121]    Step  501 : The MME receives a first page message from the MSC and sends a fifth page message to the eNodeB. The fifth page message carries at least an MT service indication. 
         [0122]    To avoid long-term MT service holding that consumes system resources and help the user make a choice regarding the MT service, the MT service request may further carry a preset call hold timer length and/or MT service related information. 
         [0123]    Step  502 : The eNodeB broadcasts the fifth page message in the cell it manages. 
         [0124]    Step  503 : After the UE receives the fifth page message, the UE notify the user of the MT service. 
         [0125]    The CS fallback method provided in the embodiments of the present invention and the specific implementation procedures are described above. 
         [0126]    For a user-held MT service, if the user chooses to continue the service, the MT service needs to be restored. When the user requests restoration of the MT service, if the UE starts a timer when the MT service is held, the UE needs to check whether the timer has expired. If the timer has expired, the restoration procedure is over. If the timer has not expired, the restoration procedure is executed. With respect to the above MT service restoration procedure, an embodiment of the present invention provides a signaling flow for MT service restoration. As shown in  FIG. 6 , the signaling flow includes: 
         [0127]    Step  601 : If the UE is currently in idle mode, the UE sends a service request to the MME. When the UE becomes active from the idle mode, step  602  is executed. If the UE is in active mode, step  602  is executed directly. 
         [0128]    Step  602 : The UE sends a first MT service activation request to the MME, requesting to restore the held MT service. 
         [0129]    The MT service activation request may carry the ID of the MT service to be activated so that the MME can determine the MT service. In certain scenarios (if the UE holds only one service), the MT service ID may not be carried, which does not impact the implementation of the present invention. 
         [0130]    Step  603 : The MME sends a second MT service activation request to the MSC. 
         [0131]    Step  604 : After the MSC receives the second MT service activation request, the MSC matches the MT service ID with the held MT service. If the service exists, the MSC accepts the activation request, stops the call hold timer, allocates the requested resource, and sends a second MT service activation response to the MME. The second MT service activation response carries a cause value of the successful operation. Otherwise, the MSC rejects the activation request and sends a second MT service activation response to the MME. The second MT service activation response carries a cause value of the failed operation. 
         [0132]    In addition, if the call hold timer in the MSC expires, the MSC stops holding the MT service, releases the held resource, and stops the timer. 
         [0133]    Optionally, different response messages may be sent to the MME in the scenarios of success and failure. The response message may also carry the MT service ID to help the UE determine the MT service. 
         [0134]    Step  605 : When the MME receives the second MT service activation response, the MME may send a first MT service activation response to the UE. 
         [0135]    The first MT service activation response may carry the MT service ID carried in the second MT service activation response. Alternatively, the MME may not send the first MT service activation response and the implementation of the present invention will not be impacted. 
         [0136]    Step  606 : The MME sends a PS service handover request to the eNodeB. 
         [0137]    In practice, the MME may proceed without handing over the current PS service of the UE according to the configured network operation policy and therefore the MME does not need to send a PS service handover request to the eNodeB and the eNodeB does not need to execute the PS handover procedure. 
         [0138]    Step  607 : The eNodeB receives the PS service handover request and initiates a PS service handover procedure to hand the UE over to the 2G/3G network. 
         [0139]    Step  608 : After the UE is handed over to the 2G/3G network, the UE sends the first page response and completes the MT service processing. 
         [0140]    The above describes the CS fallback method provided in the embodiments of the present invention. In the CS fallback scenario, an SMS MT service may be sent to the UE via signaling of the UE in the EPS network without the need to hand over the UE to a 2G/3G network. For example, the first page message may carry the short message content and then the short message is sent to the UE via the EPS network. The UE receives the short message and completes related processing. 
         [0141]    Those skilled in the art may understand that all or part of the steps of the method in the above embodiments of the present invention may be implemented by hardware under instructions of a program. The program may be stored in a computer-readable storage medium. When the program is executed, the following steps are performed: 
         [0142]    by an MME, receiving an MT service indication from an MSC; 
         [0143]    sending the MT service indication to a UE; and 
         [0144]    receiving an MT service response returned by the UE and performing subsequent operations according to the MT service response. 
         [0145]    The storage medium may be a read-only memory, a magnetic disk or a compact disk. 
         [0146]      FIG. 7  shows a CS fallback system provided in an embodiment of the present invention. The system includes: an MME  701 , an MSC  702 , and an eNodeB  703 . 
         [0147]    The MSC  702  includes a service indication sending unit  7021 . 
         [0148]    The service indication sending unit  7021  is configured to send an MT service indication to the MME  701  after receiving the MT service indication. 
         [0149]    The MME  701  provided in the embodiment of the present invention includes: 
         [0150]    a page message receiving unit  7011 , configured to receive the MT service indication from the MSC  702 ; 
         [0151]    an MT service notifying unit  7012 , configured to send the MT service indication to a UE  704 ; 
         [0152]    a response receiving unit  7013 , configured to receive the MT service response returned by the UE  704 ; and 
         [0153]    a response processing unit  7014 , configured to perform subsequent operations according to the MT service response. 
         [0154]    In practice, the MT service response carries a user choice result and the response processing unit  7014  includes: 
         [0155]    a first response processing unit, configured to return an MT service Reject message to the MSC  702  if the user chooses to reject the MT service; 
         [0156]    a second response processing unit, configured to return an MT service Hold message to the MSC  702  if the user chooses to hold the MT service; and 
         [0157]    a third response processing unit, configured to trigger the UE  704  to access a 2G/3G network if the user chooses to accept the MT service or if the user choice result is null. 
         [0158]    To enable the UE to restore the held MT service, the MME  701  further includes: 
         [0159]    an activation request receiving unit, configured to receive a first MT service activation request sent by the UE  704 , requesting to restore the held MT service; 
         [0160]    an activation request sending unit, configured to send a second MT service activation request to the MSC  702 ; and 
         [0161]    an activation response receiving unit, configured to receive a second MT service activation response returned by the MSC  702  and indicates to the UE  704  that the UE  704  should access the 2G/3G network. 
         [0162]    The MSC  702  further includes: 
         [0163]    an activation request receiving unit, configured to receive the second MT service activation request from the MME; and 
         [0164]    an activation response sending unit, configured to return the second MT service activation response after the activation request receiving unit receives the request. 
         [0165]    Because some UEs are in idle mode in the EPS network, to activate the UEs, the MT service notifying unit  7012  includes: 
         [0166]    a UE activating unit, configured to activate the UE  704  via the eNodeB  703 ; 
         [0167]    a state querying unit, configured to: query the state of the UE  704 , and trigger a sending unit if the UE  704  is in active mode, or trigger the UE activating unit if the UE  704  is in idle mode; and 
         [0168]    the sending unit, configured to send the MT service indication to the UE  704  if the UE  704  is in active mode. 
         [0169]    In practice, the UE activating unit has two implementations. 
         [0170]    In the first implementation, the unit includes: 
         [0171]    a page message sending unit, configured to send a second page message to the eNodeB  703 ; and 
         [0172]    a service request receiving unit, configured to trigger the MT service notifying unit  7012  after receiving the service request returned by the UE  704 . 
         [0173]    In the second implementation, the UE activating unit is an activating and notifying unit. 
         [0174]    The activating and notifying unit is configured to send a third page message that carries an MT service indication to the eNodeB  703 . By sending the third page message to the eNodeB  703 , the UE is activated and the MT service indication is sent to the UE. 
         [0175]    An embodiment of the present invention provides an MME for processing of the SMS MT service in a CS fallback scenario. The MME may include: 
         [0176]    a receiving unit, configured to receive a short message from an MSC; 
         [0177]    a state judging unit, configured to judge whether a UE is in active or idle mode; 
         [0178]    a sending unit, configured to send the short message received by the receiving unit to the UE when the state judging unit determines that the UE is in active mode; 
         [0179]    an activating and sending unit, configured to activate the UE when the state judging unit determines that the UE is in idle mode and send the short message received by the receiving unit to the activated UE; and 
         [0180]    a short message response receiving unit, configured to receive a short message response from the UE. 
         [0181]    The activating and sending unit may include: 
         [0182]    a page sending unit, configured to send a second page message to the eNodeB; 
         [0183]    a returned message receiving unit, configured to receive a service request returned by the UE; and 
         [0184]    a short message sending unit, configured to send the short message to the UE according to the service request received by the returned message receiving unit. 
         [0185]    Or, the activating and sending unit may include: 
         [0186]    a page sending unit, configured to send a third page message that carries the short message to the eNodeB. 
         [0187]      FIG. 7  shows the UE  704  provided in an embodiment of the present invention. The UE  704  includes: 
         [0188]    a notification receiving unit  7041 , configured to receive the MT service indication sent by the MME  701 ; 
         [0189]    an notifying unit  7042 , configured to notify the user of the MT service after the notification receiving unit  7041  receives the MT service indication; and 
         [0190]    a response sending unit  7043 , configured to return an MT service response to the MME according to the choice of the user regarding the MT service. 
         [0191]    To make the held MT service restorable, the UE may further include: 
         [0192]    an activation request sending unit, configured to send a first MT service activation request to the MME, requesting to restore the held MT service. 
         [0193]    Further, the UE may include an MT service processing unit, configured to process the MT service. 
         [0194]    Although the present invention has been described through several exemplary embodiments, the invention is not limited to such embodiments. It is apparent that those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the present invention. The invention is intended to cover the modifications and variations provided that they fall within the scope of protection defined by the following claims or their equivalents.