VoLTE and the IMS Course Details:

In this course, you will learn about VoLTE, IMS, and the SIP protocol. This class thoroughly covers call flow through the EU-TRAN, the EPC, and into the IMS core. We will back up all that we teach with call flows and live labs using an IMS platform. This course also covers enough of other technologies like Diameter and DNS, providing you with a clear understanding of the complete picture. The lessons in this course are clear, very technical, and always practical, and since much of it is hands-on, you can investigate and reinforce the knowledge you've acquired from each lesson.

    No classes are currenty scheduled for this course.

    Call (919) 283-1653 to get a class scheduled online or in your area!

1. IMS Architecture and SIP Proxies

  • Components: HSS, Proxy-CSCF, Serving-CSCF, Interrogating-CSCF, and Policy Decision Function
  • IMS Identifiers
  • IMS Message Paths Introduction (Via and Record-Route)
  • The Service Path
  • Initial Filter Criteria Introduction

2. IMS Identifiers

  • IMSI
  • UICC
  • Home Network, Public ID, and Private ID
  • SIP URI Format

3. SIP Architecture

  • Requests and Responses
  • SIP Message Flow
  • SDP Introduction

4. SIP Via Paths

  • The Via: Header
  • Establishing the Response Path
  • Forking—Response Merging
  • Loops and Spirals
  • Max Forwards

5. SIP Route Headers

  • Route Path vs. Via Path
  • Record-Route and Route Headers
  • Establishing the Route Path
  • The Role of the S, I, and P Proxies

6. IMS Service Path

  • The Service Path
  • Path Header (RFC 3327)
  • Service-Route (RFC 3608)


  • AVPs
  • SCTP vs. TCP
  • IMS Command Values
  • IMS DIAMETER Example

8. Initial Filter Criteria

  • The User Profile
  • How the iFC Is Used
  • Understanding XML
  • Disjunctive and Conjunctive Normal Form

9. Basic SIP and IMS Specific Headers

  • Via, Branch, Max-Forwards
  • SIP Dialog (To, From, tag= fields, Call-ID:)
  • CSeq, Contact: Expires:
  • Proxy-Authenticate:, Proxy-Authorize:
  • User-Agent:, Allow:, Supported:
  • Content-Type:, Content-Length:
  • P-Access-Network-Info
  • P-Charging-Vector:, P-Preferred-Identity:, P-Asserted-Identity:, Authorization:
  • Security-Client:, Security-Server:
  • IMS Signaling Compression (SigComp Architecture)

10. Session Description Protocol (SDP)

  • Session Parameters
  • SDP Format
  • Extending SDP
  • SDPng
  • Media Negotiation
  • Changing Session Parameters

11. QoS, Real Time Media, and RTP

  • How Packet Loss, Jitter, and Latency Affects Voice
  • Making Voice and Data Coexist Efficiently
  • QoS Explained: What It Is and How It Works
  • QoS Criteria
  • QCI Table: 1-4 vs. 5-9
  • Dedicated Bearer When We Need to Change QoS
  • Dedicated Bearers
  • Dedicated Bearer Establishment
  • Sketch Network View of UE with Both Default and Dedicated Bearers
  • GBR or Non-GBR
  • MBR
  • Scheduling Resources for GBR Bearers vs. Not Scheduling for Non-GBR
  • Signaling for a Dedicated Bearer (E/W Diagram)
  • Channel Quality Indicator (CQI)
  • Mechanism for Sending Data to UE in Downlink
  • How Uplink Scheduling Differs from Downlink
  • Uplink and Downlink Operations to the Associated LTE Physical Channels
  • Uplink and Downlink Data Scheduled Every Subframe

12. Presence

  • SIMPLE: SIP for Instant Messaging and Presence Leveraging Extensions
  • Terminology
  • Framework
  • Resource List Manipulation Requirements
  • Authorization Policy Manipulation
  • Acceptance Policy Requirements
  • Notification Requirements
  • Content Requirements
  • General Requirements

13. Charging and New Services within the IMS

  • Charging Entities and Functions
  • P-Headers Related to Charging
  • Diameter and How It Is Used for Ro Interface

14. IMS Call Flow Examples

  • LTE Attach Based on an Actual Trace
  • Open-IMS Register
  • Open-IMS Invite
  • Open-IMS Chat Message
  • Open-IMS Instant Message
  • IMS SIP Register from an Actual Trace
  • IMS Invite from an Actual Trace

15. IMS and the DNS

  • DNS Basics
  • A-Record
  • The SRV Record (RFC2782)
  • How SIP Uses the SRV Record (RFC3263: Locating SIP Servers)
  • How to Configure a SRV Record
  • The NAPTR Record (RFC 2915)
  • How the P-CSCF Locates the I-CSCF
  • Introduction to ENUM (RFC 3761: ENUM Protocol)
  • How the S-CSCF Uses ENUM

16. SIP Timers

  • UDP and TCP Behavior
  • Session-Expires

17. IMS Access Using VoLTE

  • IMS Flow Using VoLTE
  • IMS Flow VoLTE to CS
  • User Plane and Control Plane

18. User Equipment and Radio Frequency

  • What Is User Equipment?
  • It Is All about Mobility!
  • New Requirements of 4G LTE
  • Control Signaling Overview (SIP, RCC, Diameter)
  • Information Encapsulation Methods: TLV, AVP, XML, ASN.1
  • Physical Layer Discussion
  • Types of Radio Signaling (History to LTE)
  • Types of Radio Architecture
  • Non Access Stratum Signaling
  • Signaling: OFDMA
  • 2G / 3G Fallback to LTE


  • GSM/WCDMA View
  • CDMA View
  • Single Component: eNodeB Function and Purpose
  • Interfaces: Uu, X2, S1-MME, S1-U
  • Separation of Control Plane and User Plane
  • Introduction to Paging, Idle and Power Saving
  • Introduction to Tracking Areas

20. The UE Power Up Process

  • Frequency Scanning on Power-On
  • Steps after Power-On
  • Uplink Sync on PRACH Channel
  • System Information Blocks (SIBS and Types)
  • Channel Bandwidth, MIBs, and System Frame Number (SFN)
  • Cell Selection Steps
  • Random Access Response
  • RRC Connection Request
  • RRC Connection Setup
  • RRC Connection Setup Complete
  • RRC Idle State: Re-established and Released
  • UE Capability Enquiry from eNB and UE Capability Information Response
  • LTE Device Categories (1–5)
  • SIB 1 and SIB 2

21. The LTE Attach, GTP, APNs, and Default Bearers

  • Initial System Acquisition Steps
  • Key System Information Broadcast Messages
  • PRACH Channel
  • Synchronize with LTE Cell (Downlink and Uplink)
  • Request RRC Connection
  • Built in Features vs. Configured Features (IMSI, PLMN, Subscriber Info)
  • The Attach, GTP, APNs, and Default Bearer Assignment
  • Describe Network Attachment in LTE
  • Piggybacking Messages
  • Establishment of PDN Connectivity from LTE Air Interface
  • Attachment to MME: Manage Authentication and Security
  • Default Bearer (Connection to PDN)
  • SIP Signaling into the IMS

22. Downlink and Uplink Behavior

  • Downlink
  • Channel Quality Indicator (CQI)
  • Dynamic CQI Signaling and QAM
  • Reference Signal
  • CQI Report (PUCCH)
  • CQI Report and Data (PUSCH)
  • Periodic and Operator Defined CQI Reporting
  • CQI Index Table
  • DCIs
  • Uplink
  • Uplink Operation (UE to eNodeB)
  • Uplink Signaling
  • Scheduling Request on PUCCH
  • DL Control Information (DCI) on PDCCH
  • Buffer Status Report (BSR) on PUSCH
  • eNodeB Scheduler
  • UL Grand on PDCCH
  • Send Data on PUSCH

23. Idle Mode Within and Beyond the UE

  • Current Battery Technologies and How They Work
  • Saving the Battery and Operator Resources
  • Power Saving Features
  • Inactivity Timer
  • Default Bearers Maintained in EPC During Idle
  • Contexts Removed in EU-TRAN During Idle
  • UE Context Release Request
  • UE Context Release Command
  • RRC Connection Release
  • UE Context Release Complete
  • State of EPC Bearers During Idle Mode with S-GW Buffering
  • Why Paging Is Necessary
  • Idle Mode "Always On" Activities (Cell Reselection, Tracking Area Update, Monitor for Paging, and Exit Idle Mode)

24. Tracking and Paging a UE

  • Why Tracking and Paging Is Necessary
  • Entities Involved in Tracking and Paging a UE
  • Tracking Areas (TAIs)
  • Tracking Area Update (TAU)
  • Paging to TAIs
  • TAU Keep Alive for UE
  • TAU Request, Authentication, EPC bearers, TAU response, TAU complete
  • T3450 Timer
  • GUTI
  • Paging Process from E-UTRAN
  • Bearer States During Idle Mode
  • S-GW Buffering During Idle Mode
  • RSRP
  • RRC_Idle
  • Service Request
  • Cell Reselection

25. Handover Between eNodeBs

  • The Need for UE Mobility and Cell Reselection
  • Cell Reselection Criteria
  • Home network Cell
  • PLMN Identity
  • "Barring" Status Check
  • Handover Between eNodeB
  • Identify Types of Handover in LTE
  • Measurements and Measurement Reporting (Event Driven vs. Periodic Driven)
  • Stages of Handover
  • Handover Coverage Areas
  • LTE Hard Handover: Serving Cells and Target Cells
  • RRC Connection Reconfiguration Message: Measurement Criteria (Absolute or Relative) and Measurement Reports
  • Handover Prep, Execution, and Completion
  • Handover Packet Buffering by SGW
  • Handover Data Forwarding Tunnel

*Please Note: Course Outline is subject to change without notice. Exact course outline will be provided at time of registration.
  • IMS architecture
  • IMS and the DNS
  • IMS access using VoLTE

Lab 1: Start the IMS
Lab 2: How to Bounce Your IMS (Reference)
Lab 3: Manage Your IMS
Lab 4: Alice IMS User Addition
Lab 5: Bob IMS User Addition
Lab 6: Configure Linksys Phone as Bob
Lab 7: Using IMS Droid with the IMS
Lab 8: How to Use Wireshark (Reference)
Lab 9: Wireshark Call Flow – REGISTER
Lab 10: Wireshark Call Flow
Lab 11: Service Profile Walkthrough
Lab 12: iFC for TAS
Lab 13: DNS Configuration Walkthrough
Lab 14: ENUM

  • Individuals who need to understand how LTE networks carry voice and other real time services
  • Anyone who works on a narrow part of 4G networks that needs to understand what the surrounding components do

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