Voice over LTE (VoLTE) is the backbone of modern voice communication in 4G and beyond. However, its underlying architecture—IMS (IP Multimedia Subsystem)—is often considered complex, fragmented, and difficult to understand.
This course is designed to demystify VoLTE and IMS by explaining concepts clearly, logically, and step by step—starting from mobile network fundamentals and progressing all the way to real-world VoLTE call flows, LTE procedures, and SRVCC evolution.
Whether you are a telecom engineer, network planner, NOC engineer, student, or instructor, this course will give you a solid conceptual and practical understanding of how voice works over LTE networks. Here is the outline of the course:
Section 1: Introduction VOLTE
- Three main components of a mobile network
- Evolution of voice services from 2G to 4G
- GSMA profile for Voice over LTE (VoLTE)
Section 2: IMS – The Bigger Picture
- Introduction to IP Multimedia Subsystem (IMS)
- IMS architecture: different layers
- IMS control layer
- Call Session Control Functions (CSCFs):
- Proxy-CSCF (P-CSCF)
- Interrogating-CSCF (I-CSCF)
- Serving-CSCF (S-CSCF)
Section 3: IMS User Identities
- IMS Private Identity (IMPI)
- IMS Public User Identity (IMPU)
- Service profile
- SIP User Agent (SIP-UA)
Section 4: High-Level IMS Procedures
- IMS public connectivity requirement
- EPS bearers for IMS connectivity
- IMS integration in 4G
- IMS registration: P-CSCF discovery
- UE registration with IMS in VoLTE (signal flow)
- End-to-end signaling path for call setup
- End-to-end SIP signaling for call setup and media bearer establishment
- IMS media bearer teardown
Section 5: Voice Codecs for VoLTE
- Speech codecs for Voice over IP
- VoLTE codecs
- Different speech qualities
- Narrowband and wideband Adaptive Multi-Rate (AMR) codecs
- Enhanced Voice Services (EVS) codecs and operating modes
