It is a technology whereby voice and SMS services are delivered to LTE devices through the use of GSM (global system for mobile communications) or another circuit-switched network.
The 3GPP specifications support two main approaches for the delivery of voice over LTE. The main short-term solution is circuit switched fallback, in which the mobile accesses the circuit switched domain of a legacy 2G or 3G network by moving to a 2G or 3G cell. The main long-term solution is the IP multimedia subsystem, an external network that handles the signalling functions needed for voice over IP. There are also three other approaches: the delivery of voice over IP services by a third party, the use of a dual radio device and another 2G/3G inter-working technique known as voice over LTE by generic access. Each approach can be adapted for the delivery of text messages, using either SMS or a proprietary messaging application.
#CSFB #Circuit-SwitchedFallback #VoLTE #IMS #LTE #4G #UMTS #3G #GSM #2G
