VoLTE provides five benefits over traditional CS voice calls.
VoLTE enables operators to migrate their circuit switched infrastructure (e.g. 3G) to a fully IP centric network. Without VoLTE, 4G networks cannot support voice service, therefore operators wishing to offer this communication capability will need to still support legacy technologies and use CSFB (CS Fallback) techniques to redirect the user towards them when a call is made or received.
VoLTE offers higher voice quality than legacy circuit switched voice. As shown in Figure 1, VoLTE provides voice in wider range of frequency and enhances the voice quality significantly. With implementation of EVS (Enhanced Voice Services) codec, the range is even extended, and customers can enjoy very high-quality voice.
Another prominent advantage of VoLTE is the shorter call setup time compared to legacy circuit switched voice services. Call setup time is the time it takes from initiating the call to hearing from or speaking to the called party, and VoLTE reduces the call setup time to about a third of that of legacy circuit switched voices.
VoLTE also enables video calls to be provided in conjunction with HD voice (ViLTE: Video over LTE). This means that not only video calls are possible between VoLTE subscribers, but also switching between Video and Voice is supported.
As VoLTE calls are natively supported by LTE networks, the scarce radio resources are used much more efficiently than with legacy technologies.
IPLOOK has developed IP multimedia subsystem (IMS) products that incorporate IMS applications which are installed on hardware devices built to the Advanced Telecom Computing Architecture (ATCA) standard (the leading hardware standard for telecom carriers), and which form the core networks of mobile phone services. IPLOOK also provides telecom carriers with solutions that help them deliver a wide range of optimized voice services.
IPLOOK’s IMS products consist of a Proxy-Call Session Control Function (P-CSCF) and a Serving/Interrogating Call Session Control Function (S/I-CSCF). These are part of a control system that performs call control, a Telephony Application Server (TAS) incorporated in a service delivery system that controls additional mobile phone services, and an IMS Access Gateway (IMS-AGW) that controls packet and relays voice data.
An IMS application sample is shown in Figure 2. As this makes clear, introduction of IMS products to a telecom carrier’s core network makes it possible to offer Voice over LTE (VoLTE) service in which voice calls using the LTE communication system are possible. This supports voice calls and video calls with high sound quality, minimal delay, and high stability. Moreover, high-speed data communication can be used even during a call.
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