Virtual Classroom Training

€ 2780 *


€ 2780 *


€ 1950 *
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Course outline

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The EPS and IMS network architecture and procedures for the voice service in VoLTE solution will be presented, on a level allowing understanding and analysing SIP and Diameter traces from a VoLTE environment. The course includes the enhanced SRVCC solution with the ATCF/ATGW deployment. A significant part of the time will be devoted to hands-on exercises with Wireshark-based traces, with focus on the messages and parameters for the VoLTE-specific traffic cases.


This is a theoretical training with practical exercises. The exercises are hands-on and require the participants to have a laptop with the Wireshark analyzer software installed.


Knowledge of the IMS network architecture is assumed, as well as a general understanding of signalling principles in telecom networks. Attending Apis “VoLTE – Voice over LTE” course prior to this event, or having the equivalent knowledge, is necessary.

Brief overview of IMS network architecture

  • IMS subscription: Service Profile and Filter Criteria
  • IMS identities: IMPI, IMPU, GRUU, ICSI
  • Roles of basic core IMS nodes: P-CSCF, I-CSCF,    S-CSCF, SLF, HSS/UPSF and AS
  • IMS breakout: BGCF, MGCF, MGW, ENUM roles
  • Roles of IMS nodes for additional user plane handling functions: IMS-ALG/IMS-AGW, IBCF/TrGW, MRFC/MRFP, ATCF/ATGW
  • Policy and Charging Control: PCRF, SPR

SIP and Diameter basics

  • SIP addressing and routing functions, SIP and tel URI identifiers, SIP nodes, DNS usage
  • SIP as an application layer protocol
  • Diameter addressing and routing functions, Diameter Identity, DEA/DRA nodes, DNS usage
  • Diameter as an application layer protocol

Birds-eye view of Voice over LTE profile for IMS (VoLTE)

  • Life cycle of a UE in a VoLTE environment: power-up sequence, LTE Attach, PDN Connection Establishment, IMS Registration, Invitation, SRVCC
  • Requirements on UE, the LTE and the IMS nodes

Impact of VoLTE on the network nodes

  • VoLTE-specific parameters in HSS
  • Identities used for call anchoring and for SRVCC: STN-SR, ATU-STI, C-MSISDN
  • Functionalities and usage of TAS and SCC AS

Access Attach for VoLTE

  • VoLTE-specific parameters and settings at LTE Attach and PDN Connection Setup
  • APN and QoS recommendations for Default Bearers

IMS Registration for VoLTE

  • IMS Registration : SIP extensions in VoLTE
  • ATCF/ATGW inclusion at IMS Registration
  • IMS Access Network Security: SIP extensions for AKA and IPsec
  • The Registration traffic case with analysis of a trace

IMS Invitation for VoLTE

  • IMS session setup: SIP extensions in VoLTE
  • Service handling in IMS: TAS and Supplementary Services handling
  • Access Domain Selection for voice call delivery decision: PS vs CS
  • IMS QoS handling: SIP extensions for preconditions, Diameter on Gx and Rx for PCRF inclusion
  • Session anchoring in ATCF/ATGW
  • User Plane manipulation: transcoding, functions at the network border
  • The IMS session setup traffic case with analysis of a trace

Single Radio Voice Call Continuity (SRVCC)

  • Functions of network elements involved in SRVCC: ATCF/ATGW, SCC AS, enhanced MSC Server
  • SRVCC Access Transfer: SIP extensions at IMS registration and session setup in enhanced SRVCC
  • The SRVCC traffic case

A peek into VoLTE interworking

  • Integrating CS domain with IMS: MSC Server enhanced for ICS
  • A birds-eye view of the ICS procedures from the GERAN/UTRAN access
  • Life cycle of a UE in a ICS environment: power-up sequence, CS Attach, PS Attach and PDP Context Activation, IMS Registration from the MSC, CS call anchored in IMS, rSRVCC
  • A short discussion of the VoHSPA and VoWiFi options
This course presents the VoLTE/SRVCC signalling for the voice service. It is designed for participants that will work with traces from the IMS/VoLTE networks.

Interested in IMS Signalling for VoLTE?

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