Increasing demands for diversified network services are the major impetus for the evolution of telecommunication networks. As one of the essential parts of network services, voice service has experienced ongoing evolvement over these years.
CS Core provides CS voice solutions for subscribers in the 2G/3G network.
In the 4G all-IP era, Voice over Long Term Evolution (VoLTE) provides an IP-based voice service directly through the IMS and LTE network.
While with a view to ensuring the continuity of voice services in various phases of 4G network deployments, Circuit Switched Fallback (CSFB/CS Fallback) and Single radio voice call continuity (SRVCC) alike interim voice solutions are introduced in the 4G network. Here are a brief introduction to CSFB and SRVCC:
CSFB: If a UE is camped on LTE but it does not support VoLTE, it needs to perform a CSFB to initiate a voice call. CSFB is a mechanism that sends the user from 4G to 2G/3G (CS RAT) where it can successfully complete a CS Voice Call.
SRVCC: It provides a solution for handing over VoLTE (Voice over LTE) to 2G/3G networks. To make it interoperable with existing networks, these calls are to be handed over to Circuit switched calls in GSM/WCDMA networks.
· In 5G NSA network: VoLTE, VoNR, EPS fallback
In the initial phase of 5G deployment, to ensure user experience in voice and data, large-scale commercialization of 5G needs to be premised on a complete VoLTE network.
With the 5G NSA network framework, VoLTE can be achieved by connecting with EPC and eNodeB; VoNR can be achieved by connecting with EPC and gNodeB.
Evolved Packet Switched Fallback (EPS FB/EPS fallback) enables 5G phones to use the 5GC with NR for all data traffic, but RAN may trigger moving the phone connected to EPC, which is the best option to redirect the 5G devices from 5GC to EPC to make a VoLTE call in the transitory stage.
· In 5G SA network: VoNR, EPS fallback
In 5G SA networks, there are two options for 5G voice service: 5G Voice over New Radio (VoNR) and EPS Fallback.
Voice over New Radio (VoNR) is the IP Multimedia System (IMS) based voice calling services based on 5G access, realizing both voice and data services carried on the 5G network.
As an intermediate solution, EPS fallback enables subscribers to use VoLTE or even CSFB, ensuring the continuity of voice services and seamless user experience during call establishment.
To simplify the Voice Network and improve O&M efficiency, IPLOOK’s Converged Voice Core solution integrates multiple voice networks and allows all types of subscribers (2G/3G/4G/5G/fixed-line) to access an agile and efficient all-in-one voice network, delivering high-quality 5G voice services. It also supports operators and enterprises to meet a variety of voice application scenarios.
