As communication technology has developed into fourth generation of wireless mobile telecommunications technology (4G), its entire network architecture has changed compared with second-generation wireless telephone technology (2G)/third generation (3G). Voice service is the most basic and the most important demand of wireless communication, it brings a big trouble to network operators or terminal operators to realize the voice service in 4G. A plurality of chip manufacturers and 3rd Generation Partnership Project (3GPP) organization propose different solutions for operators, including single card dual standby program of Simultaneous GSM and Long Term Evolution (SGLTE)/simultaneous voice and LTE (SVLTE), circuit domain down programs of circuit-switched fallback (CSFB), and Single Radio Voice Call Continuity (SRVCC)/voice over LTE (VoLTE). In these solutions, a single card dual standby program of SVLTE has no special requirements on the network, makes small changes to the network side, and does not require deployment of IP Multimedia Subsystem (IMS). SVLTE is thus being considered by the network operators.
Network construction of 4G is in an early stage, and 4G network coverage cannot be seamless. Even if operators adopt regional coverage in some cities and regions for reasons of cost, there are still disconnection problems with the 4G network for mobile terminals.
As shown in FIG. 1, it is assumed that, in FIG. 1 (a), a user equipment (UE) in the 3G and 4G network is on signal standby or dual standby for the 4G network. When the UE leaves 4G network coverage region, the UE may be disconnected from the 4G network and the UE may then be connected to the 2G network and 3G network as shown in FIG. 1 (b). The UE also may be connected to the 2G network as shown in FIG. 1 (c) if the UE leaves the 4G network coverage region. When the UE returns to the 4G network coverage region as shown in FIG. 1 (d), a user of the UE would prefer a rapid connection to the 4G network, but in view of power consumption of the UE, the UE cannot keep trying to find and access the 4G network.
Therefore, preventing a waste of power consumption of the UE caused by frequent and blind network searching, and making the UE be able to access a specific network (e.g., the 4G network) as quickly as possible are problematic.