VoLTE Deployment and the Radio Access Network: The LTE User Equipment Perspective
One principal goal in the evolution to LTE is the ability to deploy Voice over IP (VoIP) services such as Voice over LTE (VoLTE) alongside other services that use high-speed data. Toward that end, our industry has fittingly emphasized the realization of an IP Multimedia Subsystem (IMS) and its associated Session Initiation Protocol (SIP). IMS provides the interconnect/gateway functionalities that allow VoLTE devices to communicate with non-VoLTE devices or even non-wireless devices. SIP defines the signaling necessary for call establishment, tear-down, authentication, registration and presence maintenance, as well as, enabling supplementary services like three-way calling and call waiting.
However, focusing on these two areas overlooks the most significant goal of VoLTE: Delivering “carrier-grade” (or “telco-grade”) voice services that subscribers perceive to be as good as—or better than—legacy voice services.
This concept fundamentally differentiates VoLTE from other VoIP services. Ensuring “carrier-grade” voice requires the marriage of IMS and SIP with a number of LTE Radio Access Network (RAN) features. It is this combination of IMS, SIP and RAN features that ultimately provides the “carrier-grade” VoLTE experience. This white paper identifies new and necessary RAN features and discusses how each improves the quality of VoLTE service.
The white paper is part of a suite of associated literature available from Spirent. Others include:
Provides an overview of IMS, including its architecture and applications from the perspective of LTE User Equipment (UE).
Discusses related procedures, protocols and sample call flows (including VoLTE).