Voice over Wi Fi


Voice over WiFi

Length: 2 days


The Voice over WiFi course describes how WiFi access is used for operator-controlled 3GPP voice calls (sometimes referred to as WiFi calling). The course explains how (U)SIM-based terminals/UEs get IP-connectivity to the Evolved Packet Core over non-3GPP access (namely WiFi), and how IMS is used as service platform for voice calls.

The focus in the course is on un-trusted non-3GPP access with IPsec establishment between UE to ePDG and with GTP used on S2b interface. The course outlines how EPS Bearers for voice calls (for SIP and RTP) are set up in non-3GPP access. Security procedures using with EAP-AKA and IKEv2 are described. The basic IMS architecture is described, as well as procedures for registration and VoWiFi call setup (invitation). Mobility scenarios between WiFi and E-UTRAN accesses are discussed, including scenarios using ANDSF for providing the UE with rules and policies related to network discovery and selection. Scenarios where the UE has multiple simultaneous PDN connections are discussed and concepts like Multiple Access PDN Connection (MAPCON), IP Flow Mobility (IFOM) and Non-Seamless WLAN Offload (NSWO) are outlined.


General knowledge about 3GPP Networks (GPRS/UMTS/EPS) as well as general knowledge of IP is recommended.

Network Architecture

• Architecture description of Non-3GPP access to EPC

• Terminology and definitions, such as Trusted vs Un-Trusted access

• Nodes for un-trusted access over S2b interface – ePDG and 3GPP AAA

• Relationship between VoLTE and VoWiFi

• WiFi basics

• Why Voice over WiFi?

VoWiFi Step by Step

• General description of procedures to be executed step-by-step in order to establish a PDN  Connection over un-trusted access (S2b)

• ePDG discovery

• Introduction to EAP-AKA, IKEv2

Non-3GPP Access Authentication

• EPS security and comparison to Non-3GPP access security, un-trusted access and GTP

• Traffic case: EAP-AKA procedure using IKEv2 and Diameter PDN Connection Setup

• PDN connection setup description in detail including UE IP-address allocation P-CSCF discovery

• DNS procedures for PGW selection

• IPsec tunnel and GTP tunnel establishment

IMS Architecture

• SIP and VoIP basics

• Description of concepts and nodes in IMS

• IMS Registration and Invitation procedures with WiFi access

• IMS Profiles for voice with WiFi access as specified by GSMA (IR.51, IR.92, TS.22 etc)

Multiple PDN Connections

• Multiple PDN Connection principles and description

• Recommended and un-recommended scenarios

• NSWO, MAPCON, NBIFOM, concept and description

Mobility between Accesses

• Mobility Scenarios with LTE and/or WiFi access

• How does a UE decide where to be? Role of ANDSF.

• Handover scenarios between VoWiFi and VoLTE

Trusted Access

• Nodes for trusted no-3GPP access over S2a interface

• What makes a network “trusted”?

• Attach and Bearer setup over trusted access to EPC

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