Voice Over LTE (VoLTE), SIP and the IMS

Did you know that the global IMS market the architectural foundation that makes VoLTE, VoWiFi, and the future VoNR possible is projected to grow from USD 3.42 billion in 2024 to USD 7.41 billion by 2029 at a 16.7% CAGR, driven by the accelerating shift from circuit-switched voice to fully IP-based multimedia communication over LTE and 5G networks? This compelling growth underscores the critical importance of VoLTE, SIP, and IMS expertise for engineers at the centre of modern mobile voice service delivery.

Course Overview

The Voice Over LTE (VoLTE), SIP and the IMS course by Alpha Learning Centre is meticulously designed to equip core network engineers, RAN specialists, and multimedia service professionals with essential skills in understanding VoLTE architecture, mastering SIP-based session control over IMS, analysing VoLTE call flows from device registration through to call establishment and handover, and troubleshooting VoLTE service issues using signalling trace analysis. This course covers IMS functional architecture for VoLTE, SIP and Diameter signalling, bearer management for voice QoS, SRVCC and eSRVCC handover, and VoWiFi and VoNR migration considerations.

Why Select This Training Course?

Selecting this VoLTE, SIP and IMS course offers numerous advantages for professionals working on mobile voice service delivery across LTE and 5G networks. Participants will gain structured knowledge of the complete VoLTE protocol stack from IMS registration and SIP invite procedures through to RTP bearer establishment, QoS management, SRVCC handover to 2G/3G, and the evolution pathway towards VoNR over 5G standalone networks.

For organisations, investing in this training ensures that voice service engineering teams have the depth of VoLTE and IMS knowledge required to deploy, operate, and troubleshoot IP-based voice services with confidence. Research from Mordor Intelligence confirms that Standalone 5G deployments require VoNR, which relies directly on IMS session control for call setup, codec negotiation, and QoS enforcement making structured VoLTE and IMS expertise an essential investment for any operator planning or executing a 5G SA voice migration.

Individuals who complete this course will benefit from a highly specialised and valuable technical profile in the mobile voice engineering domain. Studies confirm that carriers are accelerating VoNR rollouts and that engineers with IMS-based voice architecture expertise spanning both VoLTE and VoNR are among the most strategically valuable technical profiles within mobile operator core network and multimedia service engineering teams globally.

Transform your VoLTE and IMS capabilities Register now for this critical advanced training programme.

Who Should Attend?

This course is suitable for:

• Core network engineers working on VoLTE deployment and operations
• IMS architects and protocol engineers specialising in SIP and Diameter
• RAN engineers requiring knowledge of VoLTE bearer and QoS management
• Network operations engineers supporting VoLTE voice service quality
• Systems integrators deploying VoLTE and VoWiFi solutions
• Engineers planning migration from VoLTE to VoNR over 5G Standalone networks
• Technical consultants advising on mobile voice architecture and migration strategy

What are the Training Goals?

This course aims to:

• Explain VoLTE architecture and the role of IMS in delivering voice services over LTE
• Describe IMS registration procedures and SIP signalling flows for VoLTE call establishment
• Analyse end-to-end VoLTE call flows from UE registration through bearer setup to call teardown
• Understand QoS bearer management for voice including GBR bearer establishment and QCI values
• Explain SRVCC and eSRVCC handover procedures for VoLTE continuity to 2G/3G
• Evaluate VoWiFi architecture and the IMS integration with Wi-Fi calling services
• Assess VoNR requirements and the IMS architecture evolution for 5G voice services
• Troubleshoot VoLTE service issues using SIP and Diameter trace analysis techniques

How will this Training Course be Presented?

The Voice Over LTE (VoLTE), SIP and the IMS course employs a comprehensive and innovative approach to ensure maximum knowledge retention and technical skill development. Expert-led instruction from professionals with hands-on VoLTE deployment and IMS architecture experience forms the core of the course, combining detailed call flow analysis with practical troubleshooting workshops.

The course utilises a blend of theoretical understanding and practical applications, allowing participants to develop and demonstrate genuine VoLTE and IMS engineering competency. Advanced educational methodologies create a personalised and engaging learning journey through:

• Instructor-led sessions by experienced VoLTE and IMS deployment professionals
• End-to-end VoLTE call flow analysis workshops using annotated SIP signalling diagrams
• QoS bearer management and GBR configuration exercises
• SRVCC procedure analysis and handover scenario workshops
• Protocol trace interpretation exercises using real VoLTE signalling captures
• VoNR migration planning and IMS architecture evolution discussions

Join us now and elevate your VoLTE, SIP and IMS expertise to new heights!

Course Syllabus

Module 1: Evolution to VoLTE and Market Drivers

• Voice service evolution from 2G/3G circuit‑switched to 4G packet‑switched VoLTE.​
• Market drivers and business case for VoLTE deployment by operators.​
• GSMA PRD IR.92 specifications and VoLTE service requirements.​
• Alternative voice solutions: CS Fallback (CSFB), VoLGA, and over‑the‑top (OTT) services comparison.​
• VoLTE benefits: HD voice quality, faster call setup, spectrum efficiency, video calling.​

Module 2: LTE/EPS Network Architecture for VoLTE

• LTE system architecture: E‑UTRAN and Evolved Packet Core (EPC) overview.​
• EPC components: MME, S‑GW, P‑GW, HSS, PCRF and their roles in VoLTE.​
• EPS bearer model: default bearer and dedicated bearer concepts for voice.​
• LTE attach procedure and PDN connectivity for IMS access.​
• Radio functionality and resource allocation for voice traffic.​

Module 3: IP Multimedia Subsystem (IMS) Architecture

• IMS architecture overview and service delivery framework.​
• Call Session Control Functions: Proxy‑CSCF (P‑CSCF), Interrogating‑CSCF (I‑CSCF), Serving‑CSCF (S‑CSCF).​
• Home Subscriber Server (HSS) for subscriber data and authentication.​
• Application Servers (AS): SIP AS, telephony application server (TAS), and service logic execution.​
• Media Resource Function (MRF): MRFC and MRFP for conferencing and announcements.​
• IMS reference points and interfaces: Gm, Mw, ISC, Cx/Dx, Mg, Mr.​

Module 4: IMS Identities and Addressing

• IMS Public User Identity (IMPU): SIP URI and Tel URI formats.​
• IMS Private User Identity (IMPI) for authentication and subscription.​
• Relationship between IMPU, IMPI, and device identities (IMEI, MSISDN).​
• Public Service Identity (PSI) for application and service addressing.​
• Identity management and subscriber provisioning in HSS.​

Module 5: Session Initiation Protocol (SIP) Fundamentals

• SIP architecture: user agents, proxy servers, registrars, back‑to‑back user agents (B2BUA).​
• SIP request methods: REGISTER, INVITE, ACK, BYE, CANCEL, UPDATE, PRACK, INFO.​
• SIP response codes: provisional (1xx), success (2xx), redirection (3xx), client error (4xx), server error (5xx).​
• SIP message structure: request/status line, headers, and message body.​
• SIP transactions, dialogs, and session lifecycle.​
• SIP addressing and routing mechanisms.​

Module 6: Session Description Protocol (SDP)

• SDP purpose and role in multimedia session negotiation.​
• SDP message structure: session‑level and media‑level descriptions.​
• SDP offer/answer model in SIP‑based call establishment.​
• Media types, codecs, transport protocols, and attributes in SDP.​
• Bandwidth negotiation and quality parameters configuration.​

Module 7: Diameter Protocol in IMS

• Diameter protocol architecture and role in IMS for AAA and policy.​
• Diameter message format: commands, AVPs (Attribute‑Value Pairs), sessions.​
• Diameter applications: Cx/Dx (I‑CSCF/S‑CSCF to HSS), Sh/Dh (AS to HSS), Rx (P‑CSCF to PCRF).​
• Authentication and subscriber data retrieval via Diameter.​
• Diameter routing and transport over SCTP.​

Module 8: RTP, RTCP, and Media Transmission

• Real‑time Transport Protocol (RTP) for voice media transport.​
• RTP header structure, payload types, and sequence numbering.​
• RTCP (RTP Control Protocol) for feedback and quality reporting.​
• Voice codecs for VoLTE: AMR, AMR‑WB (Wideband), EVS (Enhanced Voice Services).​
• Robust Header Compression (RoHC) for bandwidth efficiency.​

Module 9: VoLTE Registration Procedures

• LTE attach and default EPS bearer establishment for IMS connectivity.​
• PDN connection setup to IMS domain (APN: IMS).​
• IMS registration: SIP REGISTER message flow from UE to IMS core.​
• IMS authentication using IMS‑AKA and integration with LTE authentication.​
• P‑CSCF discovery: DHCPv6, PCO (Protocol Configuration Options).​
• Registration state management and re‑registration procedures.​

Module 10: VoLTE Call Establishment and Termination

• Mobile‑originated VoLTE call: SIP INVITE flow through IMS core.​
• Mobile‑terminated VoLTE call: paging, SIP INVITE delivery, alerting.​
• SDP offer/answer exchange and codec negotiation during call setup.​
• Dedicated bearer establishment for voice media: QoS negotiation and bearer activation.​
• 180 Ringing, 200 OK, and ACK message flows.​
• Call termination: BYE request and session teardown procedures.​

Module 11: Policy and Charging Control (PCC) for VoLTE

• PCC architecture: PCRF, PCEF (P‑GW), BBERF, and their interactions.​
• Rx interface: P‑CSCF to PCRF signalling for VoLTE session policies.​
• Gx interface: PCRF to PCEF for bearer establishment and QoS enforcement.​
• QoS Class Identifier (QCI) for VoLTE: QCI 1 for conversational voice.​
• Guaranteed Bit Rate (GBR) bearers and resource reservation.​
• Dynamic policy rules and service data flow detection.​

Module 12: VoLTE Supplementary Services (MMTel)

• Multimedia Telephony Service (MMTel) in IMS Application Servers.​
• Call forwarding (unconditional, busy, no reply, not reachable).​
• Call waiting and call hold services.​
• Three‑way conferencing and multiparty calling.​
• Call transfer (blind, consultative) procedures.​
• Calling Line Identification Presentation/Restriction (CLIP/CLIR).​

Module 13: VoLTE Interworking with Legacy Networks

• VoLTE to PSTN call flows: MGCF and MGW roles.​
• VoLTE to 3G CS (Circuit‑Switched) call interworking.​
• Breakout Gateway Control Function (BGCF) for routing decisions.​
• ENUM and DNS lookup for number translation.​
• Incoming calls from CS domain to VoLTE subscribers.​

Module 14: Circuit‑Switched Fallback (CSFB)

• CSFB principles and architecture for voice service continuity.​
• CSFB call flow: combined attach, service request, and fallback to 3G/2G.​
• SGs interface between MME and MSC for CSFB signalling.​
• CSFB to GERAN and UTRAN procedures.​
• CSFB call setup delays and optimisation strategies.​

Module 15: Single Radio Voice Call Continuity (SRVCC)

• SRVCC principles and handover from VoLTE to 3G/2G CS domain.​
• SRVCC architecture: MSC Server enhanced for SRVCC, STN‑SR.​
• Basic SRVCC (bSRVCC), enhanced SRVCC (eSRVCC), and evolved variants.​
• SRVCC handover signalling flows and session continuity.​
• Reverse SRVCC (rSRVCC) from CS to VoLTE.​
• Video SRVCC (vSRVCC) for video call continuity.​

Module 16: Voice over WiFi (VoWiFi) Architecture

• VoWiFi standardisation and integration with IMS.​
• Trusted and untrusted non‑3GPP access to EPC.​
• Evolved Packet Data Gateway (ePDG) for secure WiFi connectivity.​
• IKEv2 and IPsec tunnel establishment for untrusted WiFi access.​
• ANDSF (Access Network Discovery and Selection Function) role.​
• Hotspot 2.0 (Passpoint) for seamless WiFi authentication.​

Module 17: VoWiFi Call Flows and Mobility

• VoWiFi registration and IMS PDN connection procedures.​
• VoWiFi call establishment: SIP signalling over IPsec tunnel.​
• VoWiFi to VoLTE handover and vice versa.​
• Diameter signalling (S2a, S2b) for VoWiFi authentication and policy.​
• Media streams and QoS for VoWiFi calls.​

Module 18: SMS Over IMS and Messaging

• SMS over IP architecture and IMS integration.​
• IP‑SM‑GW (IP Short Message Gateway) for SMS routing.​
• SMS over SGs for CSFB‑enabled devices.​
• Rich Communication Services (RCS) and advanced messaging over IMS.​

Module 19: VoLTE Planning and Optimisation

• VoLTE coverage planning: RSRP, RSRQ, and SINR requirements.​
• VoLTE capacity planning and traffic modelling.​
• Radio resource allocation and semi‑persistent scheduling (SPS) for VoIP.​
• DRX (Discontinuous Reception) configuration for battery life vs. latency trade‑offs.​
• Codec optimisation: AMR vs. AMR‑WB vs. EVS selection.​
• Mobile backhaul and transmission requirements for VoLTE.​

Module 20: VoLTE KPIs and Quality of Experience (QoE)

• VoLTE Key Performance Indicators: call setup success rate, call drop rate, call setup time.​
• Mean Opinion Score (MOS) for VoLTE voice quality assessment.​
• Audio Quality KPIs (AQ‑KPIs): jitter, packet loss, delay.​
• End‑to‑end QoE monitoring and optimisation across RAN, EPC, IMS, and transport.​
• UE feature group indicators (FGI) and VoLTE capability validation.​

Module 21: VoLTE Troubleshooting and Signalling Analysis

• Protocol analyser tools for VoLTE: Wireshark, NetScout, Acme Packet, EXFO.​
• Capturing and analysing VoLTE call flows: registration, call setup, bearer establishment.​
• SIP message decoding and common errors troubleshooting.​
• Diameter message analysis on Cx, Sh, and Rx interfaces.​
• Common VoLTE issues: registration failures, call setup failures, one‑way audio, call drops.​
• Root cause analysis methodologies and trace correlation techniques.​

Module 22: Practical Labs and Case Studies

• Hands‑on: LTE attach and IMS registration trace analysis.​
• Hands‑on: VoLTE call setup signalling analysis with SIP/SDP decoding.​
• Hands‑on: Dedicated bearer establishment and QoS policy enforcement analysis.​
• Hands‑on: SRVCC handover trace analysis and session continuity validation.​
• Hands‑on: VoWiFi session establishment and handover to VoLTE analysis.​
• Case studies: commercial VoLTE deployments, optimisation challenges, and best practices.​

Training Impact

The impact of VoLTE, SIP and IMS training is evident through the measurable improvements in voice service quality, fault resolution speed, and 5G voice migration readiness that organisations achieve when their core network and voice engineering teams have structured, protocol-level VoLTE expertise.

Research indicates that organisations with structured VoLTE and IMS engineering capability achieve better voice service deployment outcomes and faster resolution of IMS-related service failures. A case study from Telia’s commercial VoLTE deployment in Finland demonstrated that engineers with comprehensive IMS architecture knowledge and SIP/EPC signalling expertise were able to integrate IMS for VoLTE successfully across the network, validate end-to-end bearer management, and establish systematic troubleshooting procedures that enabled the rapid resolution of call setup failures during the first weeks of commercial service directly enabling the operator to meet its VoLTE quality commitments from launch.

These case studies highlight the tangible benefits of implementing VoLTE, SIP and IMS training:

• Improved VoLTE service quality through systematic understanding of IMS architecture, SIP call flows, and QoS bearer management
• Enhanced troubleshooting effectiveness through comprehensive SIP and Diameter trace analysis capability applied to VoLTE service issues
• Increased handover reliability through structured SRVCC and eSRVCC procedure knowledge
• Strengthened 5G voice readiness through structured understanding of VoNR architecture and IMS evolution

By investing in this advanced training, organisations can expect to see:

• Significant improvement in VoLTE service deployment quality and voice call success rates
• Improved fault resolution speed through protocol-level IMS and SIP troubleshooting capability
• Enhanced 5G voice migration readiness through structured VoNR and IMS evolution knowledge
• Increased organisational self-sufficiency through certified VoLTE and IMS engineering expertise across deployment and operations functions

Transform your career and organisational performance Enrol now to master Voice Over LTE (VoLTE), SIP and the IMS!