Network handover method, device, and system

Abstract

A network handover method is disclosed, where after UE in an LTE network requests circuit switched fallback CSFB, an MME instructs an eNB to move the UE from the LTE network to a 2G or 3G network, and requests an MSC to hand over the UE from the LTE network to a CS domain of the 2G or 3G network for the CSFB, so that the 2G or 3G network allocates a CS domain resource to the UE. After handing over to the CS domain, the UE may perform a CS domain call. By using embodiments of the present invention, an access delay is reduced when the UE accesses the CS domain of the 2G or 3G network, duration of an entire voice call is shortened, and user experience is improved.

What is claimed is: 
     
         1 . A network handover method, comprising:
 sending, by user equipment (UE) located in along term evolution (LTE) network, a request message to a mobility management entity (MME) for requesting circuit switched fallback (CSFB);   receiving, by the UE, a handover command sent by an evolved base station (eNodeB) for instructing the UE to hand over from the LTE network to a circuit switching (CS) domain of a second generation (2G) or third generation (3G) network for the CSFB, and the handover command comprises information about a CS domain wireless resource that is allocated by the 2G or the 3G network to the UE for handing over from the LTE network to the CS domain of the 2G or 3G network;   handing over, by the UE, from the LTE network to the CS domain of the 2G or the 3G network according to the handover command;   receiving, by the UE, a session release message sent by the MSC for instructing the UE to release a third session that is generated by the UE in a process of handing over from the LTE network to the CS domain of the 2G or 3G network;   wherein before receiving, by the UE, the session release message sent by the MSC, the method comprises one of the following steps:
 sending, in the CS domain of the 2G or 3G network by the UE, a CS call connection setup request message to a mobile switching center MSC for requesting the MSC to generate a first session; or 
 sending, in the CS domain of the 2G or 3G network by the UE, a call confirmation message to the MSC, responding to a second CS call connection setup request message, wherein the CS call connection setup request message is used for requesting the UE to generate a second session. 
   
     
     
         2 . The method according to  claim 1 , wherein the handover command further comprises information about a packet switching (PS) domain wireless resource that is allocated by the 2G or 3G network to the UE for handing over from the LTE network to a PS domain of the 2G or 3G network. 
     
     
         3 . The method according to  claim 1 , further comprising:
 activating, by the UE, circuit switching (CS) domain encryption according to a CS encryption algorithm identifier included in the handover command in a process of handing over from the LTE network to the 2G network or 3G network.   
     
     
         4 . User equipment (UE), comprising:
 a transceiver;   at least one processor; and   a non-transitory computer-readable storage medium coupled to the at least one processor and storing programming instructions for execution by the processor, the programming instructions instruct the at least one processor to:
 send, through the transceiver, a request message to a mobility management entity (MME) for requesting circuit switched fallback (CSFB); 
 receive, through the transceiver, a handover command sent by an evolved base station (eNodeB) for instructing the UE to hand over from a long term evolution (LTE) network to a circuit switching (CS) domain of a second generation (2G) or third generation (3G) network for the CSFB, and the handover command comprises information about a CS domain wireless resource that is allocated by the 2G or 3G network to the UE for handing over from the LTE network to the CS domain of the 2G or 3G network; 
 hand over from the LTE network to the CS domain of the 2G or 3G network according to the handover command received by the receiving unit; 
 send, through the transceiver, in the CS domain of the 2G or 3G network, a first CS call connection setup request message to a mobile switching center (MSC) for requesting the MSC to generate a first session, or send, in the CS domain of the 2G or 3G network, a call confirmation message to the MSC, responding to a second CS call connection setup request message, wherein the second CS call connection setup request message is used for requesting the UE to generate a second session; and 
 receive, through the transceiver, a session release message sent by the MSC, wherein the session release message is used for instructing the UE to release a third session that is generated by the UE in a process of handing over from the LTE network to the CS domain of the 2G or 3G network. 
   
     
     
         5 . The UE according to  claim 4 , wherein the handover command further comprises information about a PS domain wireless resource that is allocated by the 2G or 3G network to the UE for handing over from the LTE network to a packet switching PS domain of the 2G or 3G network. 
     
     
         6 . The UE according to  claim 4 , wherein the programming instructions instruct the at least one processor to:
 activate CS domain encryption according to a CS encryption algorithm identifier included in the handover command in a process of handing over from the LTE network to the 2G network or 3G network.   
     
     
         7 . A non-transitory computer readable medium comprising computer program codes stored thereon, executable by one or more digital processors for providing system configurations, the computer program codes including:
 instructions for sending a request message to a mobility management entity (MME) for requesting circuit switched fallback (CSFB);   instructions for receiving a handover command sent by an evolved base station (eNodeB) for instructing the UE to hand over from a long term evolution (LTE) network to a circuit switching (CS) domain of a second generation (2G) or third generation (3G) network for the CSFB, and the handover command comprises information about a CS domain wireless resource that is allocated by the 2G or 3G network to the UE for handing over from the LTE network to the CS domain of the 2G or 3G network;   instructions for handing over from the LTE network to the CS domain of the 2G or the 3G network according to the handover command;   instructions for sending in the CS domain of the 2G or 3G network, a first CS call connection setup request message to a mobile switching center (MSC) for requesting the MSC to generate a first session, or send, in the CS domain of the 2G or 3G network, a call confirmation message to the MSC, responding to a second CS call connection setup request message for requesting the UE to generate a second session; and   instructions for receiving a session release message sent by the MSC for instructing the UE to release a third session that is generated by the UE in a process of handing over from the LTE network to the CS domain of the 2G or 3G network.   
     
     
         8 . The non-transitory computer readable medium according to  claim 7 , wherein:
 the handover command further comprises information about a packet switching (PS) domain wireless resource that is allocated by the 2G or the 3G network to the UE for handing over from the LTE network to a PS domain of the 2G or 3G network.   
     
     
         9 . The non-transitory computer readable medium according to  claim 7 , wherein the computer program codes include:
 instructions for activating CS domain encryption according to a CS encryption algorithm identifier included in the handover command in a process of handing over from the LTE network to the 2G network or the 3G network.