Volte Training

Introduction to VoLTE (Voice over LTE)

What is VoLTE?

LTE Voice Solution Alternatives

Overview of CSFB, SRVCC and Voice over IMS

Introduction of Circuit Switched FallBack (CSFB)

EPS Reference Architecture for CSFB with UTRAN

Voice over LTE via GAN (VoLGA)

The aim of VoLGA

High-level VoLGA Service Diagram

Introduction of Single Radio Voice Call Continuity (SRVCC)

Rich Communication Suite (RCS)

EPS Reference Architecture for Single Radio Voice Call Continuity (SRVCC) to UTRAN as Destination Network


SRVCC from LTE to 3GPP2 C2K

All IP voice and video, IMS

LTE voice evolution—all-IP network

VoLTE Network Configuration with IMS

VoLTE System Architecture

Evolved Packet Core (EPC)

EPC Entities and Functionalities

EPS Mobility Management

EPS Session Management and QoS

IP Multimedia Subsystem (IMS) Architecture

Home Subscriber Server (HSS)

Policy and Charging Rule Function (PCRF)

Overview of IMS Profile for Voice and SMS

UE and Network Protocol Stacks in IMS Profile for Voice

Supplementary Service Supported in VoLTE

AMR codec and AMR-WB codec

LTE RAN Features Reference

Semi-Persistent Scheduling 3GPP 36.321

Transmission Time Interval (TTI) Bundling 3GPP 36.321

Discontinuous Reception (DRX) 3GPP 43.013

Robust Header Compression (RoHC) IETF RFC4815

IMS resource and media control elements

Signaling and transport interworking elements

Session Control in the IMS

Media Encoding

Media Transport

SIP and Diameter in the IMS

Interfaces and Protocols

IMS Architecture, Interfaces and Protocols

CSCF (Call Session Control Function)

S-CSCF (Serving-CSCF)

I-CSCF (Interrogating-CSCF)


HSS (Home Subscriber Server)

SLF (Subscription Locator Function)

Policy Decision Function (PDF)

AS (Application Server)

MGCF (Media Gateway Control Function)

MGW (Media Gateway)

BGCF (Breakout Gateway Control Function)

IP Multimedia Service Switching Function (IM-SSF)

Media Resource Function Controller (MRFC)

Media Resource Function Processor (MRFP)

IMS Operational Scenarios for VoLTE


IMS Public User Identity

IMS Private User Identity

Identification of User’s Device

Identification of Network Entities

Identification of Services (Public Service Identities)

IMS Private User Identity (IMPI)

IMS Public User Identity (IMPU)

VoLTE UE Registration

Subscription requirements

Supplementary services

Call Set-up

PSTN Break-out

Services in IMS Registration

Call origination and termination

Charging implications

Roaming and handovers

Quality of service

Media Resource Reservation and Policy Control

IMS Security

Privacy implications


GSMA IR.92 IMS Profile for Voice and SMS

IMS Feature Set

Support of generic IMS functions

Supplementary Services

SMS over IPv4/IPv6

IMS Media

Voice Media

Radio and Packet Core Feature Set

Emergency Service

Roaming Considerations

GSMA IR.94 IMS Profile for Conversational Video

IMS Feature Set

Support of Generic IMS Functions

SIP Registration Procedures

Call Establishment and Termination

Early Media

Supplementary Services

IMS Media

RTP Payload Format Considerations

Radio and Packet Core Feature Set for Video

Bearer Considerations for Video

LTE Radio Capabilities

VoLTE Functionalities and Features

Radio Functionalities

Bearers and Scheduling

UE Radio Access Capabilities for VoLTE

LTE RAN Features

Discontinuous Reception (DRX)

Robust Header Compression (RoHC)

Policy and charging control architecture

QoS and Multiple Bearers (Default, Dedicated)

QoS Class Identifiers (QCIs)

PDN Connectivity Establishment for the VoLTE User

IMS Identification

Voice over LTE use cases

Key Technical Requirements for VoLTE

QCI Values for the Bearers

Mandatory SIP Headers

Getting Connected

Call and Media Handling

CS Fallback for Evolved Packet System

Architecture of CS Fallback for EPS

Idle Mode Signaling Reduction and Use of CS Fallback for EPS

CS Fallback Attachment

Mobile Originating and Terminating

Call Using CSFB

Single Radio Voice Call Continuity (SRVCC)

Mobile Terminating Roaming Retry and Forwarding

IMS Profile for Voice and SMS

Telephony service and supplementary services

IMS control and media

IP flow and bearer management

LTE radio capabilities

Multi-media Telephony (MMTel) Supplementary Services

A range of Codes used in IMS and Mobile networks

Service Centralization and Continuity Application Server (SCC AS)

PSTN interworking

VoLTE Signaling protocols

VoLTE Call Scenarios

Bearer Concept & QoS-Architecture

Dedicated EPS Bearer Establishment

IMS triggered during Call Establishment

Requirements of protecting VoLTE traffic

VoLTE End to End Signaling

Overview of SIP and SDP

Overview of RTP and RTCP

VoLTE Call

IMS VoLTE Procedures

PDN Connectivity

NAS Signaling

Signaling Bearer, DCCH and Attach Request

UE Authentication

Bearer Setup and EPS Attach

EPS Session Management (ESM)

UE P-CSCF Discovery

SIP Registration

Overview of AKAv2-MD5

Event Subscription

VoLTE Subscription and Device Configuration

EPS Attach for CSFB

IMS VoIP and Default Bearer Activation

IMS Registration

Constructing the REGISTER Request

UE to the P-CSCF, P-CSCF to the I-CSCF and I-CSCF to the S-CSCF

S-CSCF Challenges the UE

UE’s Response to the Challenge

Registration at the S-CSCF

The 200 (OK) Response

Third-Party Registration to Application Servers

Subscription to Registration Event Package

Re-Registration and Re-Authentication


SIP Headers and Codes

Quick Overview of AMR and AMR-WB

EPS Architecture for Voice and Messaging Support

Applied IMS Feature Set

Support of generic IMS functions

SIP Registration Procedures

IMS Media

Bearer Management

Common Functionalists

Policy and charging control architecture

Complementing IMS with CS

Attachment with E-UTRAN

CS Fallback



Call establishment

E911/emergency calls

IMS Emergency Session

PDN Connection Setup for Emergency Session

Emergency Registration

Emergency Session

Mobility and VoLTE

Roaming and IPX


Interworking solutions with 3G and WiFi

VoLTE Messaging

VoLTE Call Flows

VoLTE Call Flow – Basic IMS Registration

VoLTE/IMS Procedures PDN Connectivity (NAS Signaling)


Bearer Setup and EPS Attach

Multiple Bearers (Default, Dedicated)

QoS Class Identifiers (QCIs)

GBR and Non-GBR

Standardized QCIs for LTE

P-CSCF Discovery

SIP Registration

Event Subscription

VoLTE Call Flow


VoLTE Security

VoLTE Protection vs. Latency

Protecting VoLTE services against malicious attacks

VoLTE Service Disruption Scenarios and Mitigation

Network Failures

VoLTE Sample Examples and Case studies

Sample studies for VOLTE Call flow MO and MT

Tools and processing VoLTE Logs

Analysis and Troubleshooting techniques


Counters associated with VoLTE