1. VoLTE Technical Overview storyboard
CN A-COR
Ready to begin your journey through the VoLTE Technical Overview course?

2. Course objectives
Key functionalities and requirements for eUTRAN, EPS, IMS
What happens during LTE Attach and IMS Registration procedures
How bearers are setup
How is QoS implemented in a network that provides IMS-based VoLTE
Title: Course Objectives
On our 30 minute journey today we will explore the VoLTE topics shown.

3. LTE/IMS VoLTE Network Overview
Module 1 –
LTE/IMS VoLTE Network Overview
Title: Module 1 – LTE/IMS VoLTE Network Overview
First stop, a look at the LTE Network and IMS Network from a Voice over LTE perspective.

4. What is needed for a VoLTE call?
Terminating IMS
LTE UE B party
LTE Network
CSCF
IMS Network
EPC
MME
HSS AS
eUTRAN
What is needed for a VoLTE call?
eNodeB
PGW
SGW
LTE UE A party
PCRF
P-CSCF
I-CSCF
S-CSCF
TITLE: LTE and IMS Networks Required for VoLTE
What is needed for a Voice over LTE call?
A Voice over LTE, or VoLTE call requires an LTE network and an IMS network.
Storyline: Animate and fade question. Bring in LTE Network and IMS Network when mentioned.
User Control

5. LTE Network LTE Network IMS Network EPC eUTRAN Terminating IMS
LTE UE B party
LTE Network
CSCF
IMS Network
EPC
MME
HSS AS
eUTRAN
eNodeB
PGW
SGW
LTE UE A party
PCRF
P-CSCF
I-CSCF
S-CSCF
TITLE: LTE Network
The LTE network consists of the eUTRAN and the Evolved Packet Core (EPC). The LTE network connects the subscriber to the packet core which carries the voice traffic.
Storyline: Outline each while discussing.
User Control

6. IMS Network LTE Network IMS Network EPC eUTRAN Terminating IMS
LTE UE B party
LTE Network
CSCF
IMS Network
EPC
MME
HSS AS
eUTRAN
eNodeB
PGW
SGW
LTE UE A party
PCRF
P-CSCF
I-CSCF
S-CSCF
TITLE: IMS Network
It is the IMS that provides the voice capability. The IMS supports IP voice traffic using a SIP client with either a 4G Device or the VoLTE UE. Any interworking scenarios, with other networks such as 3G, are handled by anchoring the call in the IMS.
Storyline: Bring in IMS box at beginning of slide when mentioned.
User Control

7. VoLTE Call Flow Overview
Terminating IMS
LTE UE B party
LTE Network
CSCF
IMS Network
EPC
MME
HSS AS
eUTRAN
eNodeB
PGW
SGW
LTE UE A party
PCRF
P-CSCF
I-CSCF
S-CSCF
TITLE: VoLTE Call Flow Overview
Here is a brief look at the VoLTE Call Flow. We will explore this call flow later in our journey during the second course – Nokia VoLTE Solution.
For now, we can summarize the call flow as follows: A voice call is originated from a subscriber which triggers an invite that is sent through the network to the Terminating IMS. Quality of Service, registration, bearer setup, and services are established. Then the call begins.
User Control

8. eUTRAN and EPC LTE Network IMS Network EPC eUTRAN Terminating IMS
LTE UE B party
LTE Network
CSCF
IMS Network
EPC
MME
HSS AS
eUTRAN
eNodeB
PGW
SGW
LTE UE A party
PCRF
P-CSCF
I-CSCF
S-CSCF
TITLE: eUTRAN and EPC
Remember that an LTE network consists of an eUTRAN which is a Radio Access Network (RAN) and an Evolved Packet Core (EPC).
Storyline: Zoom on LTE Network. Automatically advance to next slide.
User Control

9. eUTRAN LTE Network IMS Network EPC eUTRAN Terminating IMS
LTE UE B party
LTE Network
CSCF
IMS Network
EPC
MME
HSS AS
eUTRAN
eNodeB
PGW
SGW
LTE UE A party
PCRF
P-CSCF
I-CSCF
S-CSCF
TITLE: eUTRAN
Storyline: Zoom on eUTRAN.
The eUTRAN contains the eNodeB. The eNodeB is connected to the mobile phone network and communicates directly with mobile handsets or user equipment (UE).
User Control

10. EPC LTE Network IMS Network EPC eUTRAN Terminating IMS LTE UE B party
CSCF
IMS Network
EPC
MME
HSS AS
eUTRAN
eNodeB
PGW
SGW
LTE UE A party
PCRF
P-CSCF
I-CSCF
S-CSCF
TITLE: EPC
Storyline: Zoom on EPC. Bring in user and control lines when mentioned.
The Evolved Packet Core, or EPC, consists of the Mobility Management Entity (MME), Serving Gateway (SGW), Packet Data Network Gateway (PGW), and Policy and Charging Rules Function (PCRF). Storyline: Bring in each yellow box when mentioned.
The EPC separates control plane functionality from data plane functionality. The data plane is also referred to as the user plane and carries user traffic. The user plane provides bearer functions and carries user data packets.
The control plane is the portion of a channel or protocol that carries signaling and control data.
User Control

11. LTE Network EPC eUTRAN MME eNodeB PGW LTE UE A party SGW PCRF S1-MME
S5/S8
PGW
S1-U
LTE UE A party
SGW Gx
PCRF
TITLE: LTE Network
The LTE Evolved Packet Core (EPC) handles session establishment and carries user traffic and signaling throughout the networks.
LTE networks are “all-IP” networks. They are only capable of packet services. Voice services are provided on top of the IP, which is called Voice over IP, or VoIP. Voice over LTE, or VoLTE provides voice service over the LTE-IP infrastructure. The VoIP data traffic is handled by the Serving Gateway (SGW) and Packet Data Network Gateway (PGW) while preserving the Quality of Service for the VoIP calls.
The LTE RAN and EPC support VoLTE with software upgrades.
Storyline: Animate interfaces to demonstrate flow. Bring in text when mentioned.
User Control

12. IMS IMS HSS AS P-CSCF I-CSCF S-CSCF CMS-8200 OpenTAS Sh Cx CFX-5000 Mw
TITLE: IMS
The IP Multimedia Subsystem (IMS) is an architectural framework for delivering internet protocol (IP) multimedia to mobile users. Examples of such communications include traditional telephony, fax, , Internet access, Web services, Voice over IP, instant messaging, WiFi, videoconference sessions, and video on demand. The IMS is required for Voice over LTE services.
Click on the IMS to learn about its components.
Storyline: Hotspot on IMS box takes learner to next slide.
User Control

13. IMS Network Elements IMS HSS AS
CMS-8200
OpenTAS
HSS AS Sh
The IMS provides features and services beyond Voice over LTE. There are many other subnetworks and network elements within the IMS. These vary from operator to operator. For our purposes those involved with VoLTE are shown. Cx
CFX-5000 Mw Mw
P-CSCF
I-CSCF
S-CSCF
TITLE: IMS Network Elements
The IMS contains the core network elements needed to provision multimedia services including voice services. The key elements of the IMS are the CMS-8200, Open TAS, and CFX As part of the IMS these elements help anchor the UE during roaming, provide voice and other media services, and select appropriate application servers, based on need.
The CMS-8200 contains the Home Subscriber Server (HSS).
The Open TAS contains the Application Server (AS).
The CFX-5000 contains the Proxy Call Session Control Function (P-CSCF), Interrogating Call Session Control Function (I-CSCF), and Serving Call Session Control Function (S-CSCF).
Click on the light bulb for more information.
Storyline: Bring in each component when mentioned. Bring in each network element when mentioned. Pop-up for light bulb note.
User Control

14. IMS Functionality IMS HSS AS P-CSCF I-CSCF S-CSCF CMS-8200 OpenTAS ShCx
CFX-5000 Mw Mw
P-CSCF
I-CSCF
S-CSCF
TITLE: IMS Functionality
The IMS supports roaming, Voice over WiFi (VoWiFi), Voice over LTE (VoLTE), and interworking with 2G and 3G networks. The UE registers with, and is authenticated by, the IMS in order to receive its services, including Voice over LTE. The IMS assures that calls are delivered to a user regardless of the network the user is in.
Storyline: Animate interfaces to demonstrate call flow.
User Control

15. Let us review what you have learned on your journey so far.
Knowledge Check appears in Storyline file.

16. LTE Attach and IMS Registration Procedures
Module 2 –
LTE Attach and IMS Registration Procedures
Title: Module 2 – LTE Attach and IMS Registration Procedures
Our journey now leads us through the LTE Attach and IMS Registration Procedures. These must happen before a Voice over LTE call can occur so it is important we are familiar with them. Let's take a look.

17. LTE Attach EPC IMS eUTRAN Terminating IMS LTE UE B party CSCF MME HSSAS
eUTRAN
eNodeB
PGW
LTE UE A party
SGW
PCRF
P-CSCF
I-CSCF
S-CSCF
User Control
TITLE: LTE Attach
LTE Attach occurs after the subscriber powers on their mobile device, or user equipment (UE), but before IMS registration. LTE Attach must take place before a voice over LTE call can occur. Let us take a closer look at the LTE Attach process.
Storyline: Bring in LTE UE A party > LTE Network > IMS Network > LTE UE B party when mentioned. Automatically advance to next slide.

18. LTE Attach Process EPC IMS eUTRAN Terminating IMS LTE UE B party CSCF
CMS-8200
OpenTAS
MME
HSS AS
eUTRAN
eNodeB
PGW
LTE UE A party
SGW
CFX-5000
PCRF
P-CSCF
I-CSCF
S-CSCF
User Control
TITLE: LTE Attach Process
Walk-through the LTE Attach process by clicking on the numbers in the slide.
Storyline: Following text will be displayed in pop-ups.
1 – The subscriber turns on their mobile device and the LTE Attach procedure begins. The eNodeB signals the MME over the S1-MME interface to establish a connection. Storyline: Animate UE A > eNB > MME; Animate HSS > MME
2 – The MME queries the HSS for the subscriber profile over the S6a interface and updates the UE location with the HSS. The user name in the request is set to IMSI, and the Radio Access Technology is set to EUTRAN for LTE access.
The HSS accesses the database and responds back to the MME with the user information. Storyline: 2-seconds pause; Animate HSS > MME
3 – Storyline: Animate MME > SGW > PGW
4 – A default bearer is setup between the SGW, PGW, and UE. Storyline: Animate SGW > PGW > UE user interface (S5/S8)
5 – The PGW assigns an IP address to the UE. Storyline: 3 second pause; Animate PGW > SGW > MME > eNode > UE; Animate fake IP Address ( ) from PGW to UE along S5/S8 interface
6 – Several messages are sent between the MME, eNodeB, and SGW. The Attach process is successful. The UE is now attached to the EPS.
7 – The PGW then identifies the address of the assigned P-CSCF. Storyline: Highlight P-CSCF.
Once the LTE Attach process is comlete, a default bearer is set up, the UE discovers the P-CSCF, and IMS Registration begins.

19. EPC EPS Bearer eUTRAN EPS bearer MME eNodeB PGW PDN LTE UE A party SGW
S1-MME
S11
S5/S8 Bearer
S1 Bearer
PDN
PGW
S5/S8
S1-U
LTE UE A party
SGW
Radio Bearer Gx
S1 Bearer
User Control
PCRF
Radio Bearer
S5/S8 Bearer
TITLE: EPS Bearer: Virtual concept - Logical association between UE and PGW
Storyline: Begin with EPS Bearer set showing… will be centered on slide.
“Bearer” is basically a virtual concept. A bearer is a set of network configurations used to provide special treatment to a set of traffic packets. The main function of a wireless radio network is to provide subscribers with transport bearers for their user data.
An LTE network has a radio bearer, S1 bearer, and S5/S8 bearer. Collectively these are called the EPS bearer. Storyline: Bring in each arrow, fade previous arrow.
The EPS bearer is a logical association between the UE and the PGW. Storyline: Fade out EPS Bearer, bring in LTE diagram.
Storyline: Bring in Radio Bearer & S1 Bearer tubes. A radio bearer between the UE and the eNodeB is connected internally with the associated S1 Bearer on the S1-U interface. The eNodeB is responsible for mapping these radio bearers to physical resources over the air interface.
Storyline: Bring in red box around S1 Bearer tube. The S1 bearer between the eNodeB and the SGW is implemented using GTP protocol which builds a GTP tunnel between the two network elements. The setup of this S1 bearer is managed by the MME. The SGW and eNodeB do not directly exchange signaling to establish this bearer.
Storyline: Bring in S5/S8 Bearer tube. The S5/S8 bearer between the PGW and the SGW is usually a GPRS Tunneling Protocol (GTP) or Mobile IP tunnel between the two network elements.
EPS bearer

20. EPC Default Bearers eUTRAN MME eNodeB PGW PDN LTE UE A party SGW PCRF
S1-MME
S11
Default Bearer
PGW
PDN
S5/S8
S1-U
LTE UE A party
SGW Gx
User Control
S1 Bearer
Radio Bearer
PCRF
S5/S8 Bearer
TITLE: Default Bearers
An EPS bearer that is established when the UE initially attaches to the network and connects to a Packet Data Network (PDN) is called a Default Bearer. Storyline: Bring in Default Bearer tube, PDN cloud and dotted line.
The MME initiates the Default Bearer creation based on the subscription information from the HSS. A Default Bearer remains established throughout the lifetime of the Packet Data Network connection to provide the UE with always-on IP connectivity to that Packet Data Network.
Default Bearers are created on a per PDN basis. Therefore, if a UE is connecting to two PDNs it establishes two Default Bearers – one for each PDN.

21. EPC Dedicated Bearer eUTRAN MME eNodeB PGW PDN LTE UE A party SGW PCRF
Default Bearer
eNodeB
S1-MME
S11
PGW
PDN
S5/S8
S1-U
LTE UE A party
SGW Gx
S1 Bearer
Radio Bearer
S5/S8 Bearer
User Control
PCRF
Dedicated Bearer – app 1
Dedicated Bearer – app 2
Dedicated Bearer – app 3
Dedicated Bearer – app 4
TITLE: Dedicated Bearer
Additional bearers can also be set up by the IMS. These additional bearers are called Dedicated Bearers. They are used to carry data for specific applications. A Dedicated Bearer allows certain types of data traffic to be isolated from all other traffic. A Dedicated Bearer is always associated with a Default Bearer. One primary Default Bearer might have multiple Dedicated Bearers assigned to it.
The EPS Bearer is the level of granularity for bearer-level QoS control in an LTE network. That is, all traffic mapped to the same EPS Bearer receives the same QoS parameters that apply to the bearer-level packet forwarding treatment between a UE and the EPC. Providing different bearer-level packet forwarding treatment simultaneously requires multiple separate EPS Bearers.

22. Traffic Flow Template (TFT)
Terminating IMS
Traffic Flow Template (TFT)
LTE UE B party
CSCF
EPC
IMS
Dedicated Bearer
Traffic Flow Template (TFT)
What traffic to deliver?
Based on:
Source & Destination IP addresses
TCP/UDP ports
CMS-8200
OpenTAS
MME
HSS AS
eUTRAN
Dedicated Bearer – transporting encoded voice packets
eNodeB
PGW
LTE UE A party
SGW
CFX-5000
PCRF
P-CSCF
I-CSCF
S-CSCF
User Control
TITLE: Traffic Flow Template (TFT)
Storyline: Open with Dedicated Bearer & TFT graphic centered.
Each Dedicated Bearer is associated with a Traffic Flow Template (TFT). A Traffic Flow Template defines which traffic should be delivered on a particular Dedicated Bearer – based on source and destination IP addresses, and TCP/UDP ports.
Storyline: Switch to network diagram.
SIP signaling is established when the UE’s client registers with the network. SIP signaling is used to establish a voice session and negotiate the session parameters. For example, which audio codec to use, bit rate, transport protocols, and which ports to use for audio. A Dedicated Bearer between the UE and the PGW/IMS is established for the express purpose of transporting encoded voice packets.
Storyline: Bring in Dedicated Bearer tube.

23. Quality of Service (QoS) Introduction
Default Bearer
Non-GBR
QCI-9
APN-AMBR
UE-AMBR
APN
IP Address
ARP
LTE QoS
Dedicated Bearer
Non-GBR
QCI 5-9
APN-AMBR
UE-AMBR
TFT
ARP
L-EBI
GBR
QCI 1-4
GBR
MBR
TFT
ARP
L-EBI
TITLE: Quality of Service (QoS) Introduction
Default Bearers are always established with a Non-Guaranteed Bit-Rate (non-GBR). Non-Guaranteed Bit Rates are used for services that do not have a strong bit rate requirement.
Dedicated Bearers may be established with either a guaranteed bit rate (GBR) or a non-guaranteed bit rate (non-GBR). Guaranteed Bit Rates are applicable for services that require guaranteed Quality of Service such as VoIP and streaming video.
In packet networks, including LTE/EPC, users have one or more bearers with a certain quality of service (QoS) ranging from fixed guaranteed bandwidth to best effort services, without any guarantee. The Default Bearer and its associated Dedicated Bearer provide connections to the same PDN with different guaranteed qualities of service (QoS). Dedicated Bearers can be established with the same APN & IP addresses of the Default Bearer but with different QoS parameters to meet specific application needs, such as IMS voice, video streaming, or IP SMS.

24. EPC eUTRAN MME eNodeB PGW PDN LTE UE A party SGW PCRF QoS 1 QoS 2 SDF
S1-MME
S11
PGW
PDN
S5/S8
Bearer
S1-U
LTE UE A party
SGW
Bearer Gx
User Control
PCRF
SDF
QoS 1
SDF
TITLE: Quality of Service at the Service Data Flow (SDF) Level
A Service Data Flow (SDF) is an end-to-end application-level packet flow between a UE and one or more devices, or application servers, in an external Packet Data Network (PDN). Triggered by the UE, the default bearer aggregates one or more service data flows (SDFs) that are transported between the two network elements.
The SDF is the level at which the EPS defines the QoS parameters. While an EPS bearer is the level at which QoS is enforced in the network, an SDF, or an SDF aggregate (i.e. collection of multiple SDFs), is carried across the EPS network in an EPS bearer. In short, a user may simultaneously establish connectivity with multiple PDNs. Each of the PDN connections for the user may support at least one default EPS Bearer, and 0 to 15 Dedicated Bearers. Each EPS bearer carries an SDF aggregate. Service Data Flows (SDF) and EPS Bearers are the entities for which QoS is defined. 4G LTE bearer structure ensures that each service receives the QoS it needs to render a greater subscriber experience, even when simultaneously using multiple applications.
QoS 2
SDF

25. MME AS HSS LTE UE A party eNodeB Internet PGW SGW Router Firewall SDF
End-to-End Service (Application QoS)
MME AS
S6a/S13
HSS
S1-MME
S11
LTE UE A party
External Bearer (Bearer end-to-end QoS)
eNodeB
Internet
PGW
EPS Bearer
S1-U SS
SGi
SGi
E-RAB
S1 Bearer
(Transport QoS)
SGW
Router
Firewall
Radio Bearer
(Radio QoS)
EPS Bearer
S5/S8 Bearer
(EPS Bearer QoS)
SDF
SDF
TITLE: Quality of Service (QoS) Control
In LTE, the PCRF is needed for QoS control. QoS is implemented between the UE and the PDN Gateway (PGW) and is applied to a set of bearers.
Dedicated bearers use Traffic flow Templates (TFT) to give special treatment to specific services, such as Voice over LTE. This allows better service for such services. Unlike 2G and 3G packet data services, which treat everything on a first-come, first-served basis, 4G LTE bearer structure ensures that each service receives the QoS it needs to render a greater subscriber experience, even when simultaneously using multiple applications.
SDF

26. Quality of Service (QoS) Parameters
EPS Bearer
QoS Parameters
QCI
Bit Rates
ARP
TITLE: Quality of Service (QoS) Parameters
The key QoS parameters for the EPS Bearer are as follows:
QoS Class Identifier (QCI): The QCI is a pointer to a set of QoS parameters. It is associated with a priority, specific delay, packet loss values, and whether the service has a guaranteed bit rate. These characteristics are used by the EPS nodes (eNB, SGW, PGW, MME) to guide them in deciding how a particular service data flow is to be processed.
Bit rates:
For EPC service data flows and bearers of type Guaranteed Bit Rate (GBR), Guaranteed Bit Rate and Maximum Bit Rate (MBR) parameters are specified.
For bearers of type Non-Guaranteed Bit Rate, the Aggregate Maximum Bit Rate (AMBR) parameter is specified as a Maximum Bit Rate value applicable to a certain aggregate of such bearers (no MBR for a single bearer is defined).
Allocation and Retention Priority (ARP): This parameter is used during congestion when not all users and their services can be accommodated. In such situations, the ARP will be used by the Admission Control Function in the eNodeB.

27. VoLTE session + features
QCI
Resource Type
Priority
Packet Delay Budget
Packet Error Loss Rate
Example Services 1
GBR 2
100 ms
10-2
Conversational Voice 4
150 ms
10-3
Conversational Video (Live Streaming) 3
50 ms
Real Time Gaming 5
300 ms
10-6
Non-Conversational Video (Buffered Streaming)
Non-GBR
IMS Signalling 6
Video (Buffered Streaming) TCP-based (e.g., www, , chat, p2p file sharing, progressive video, etc…) 7
Voice, Video (Live Streaming), Interactive Gaming 8 9
Voice traffic - QCI 1
SIP Signaling - QCI 5
Video traffic - QCI 2
other IMS media - QCI 8/9
VoLTE session + features
Default Bearer
TITLE: QCI Table – TS section
Storyline: Open with VoLTE session + features graphic centered.
A Dedicated Bearer can be subdivided into Non-GBR and GBR types. GBR is the minimum Guaranteed Bit Rate per EPS Bearer. GBRs are specified individually for uplink and downlink traffic.
Every bearer must be assigned a quality of service class identifier (QCI) to allow QoS enforcement.
3GPP defines 9 QoS Class Identifiers with values assigned for latency and loss rates. Each Dedicated Bearer can have different service quality attributes specified. The following are used in LTE to determine the QoS QCI levels for each bearer:
Packet delay - the maximum acceptable delay between the UE and the PGW.
Priority - which can be dropped when network resources become hard to find.
Packet error loss - the maximum acceptable rate of IP packets that are not successfully received by the PDCP layer.

28. Service Data Flow Level Application Level
Default Bearer – APN Internet, QCI=9 Internet Access
Default Bearer – APN IMS, QCI=5 SIP Signaling
LTE UE A party
Internet /
SIP Signaling / Voice Media
eNodeB
SGW
PGW
Dynamic Dedicated Bearer – APN IMS, QCI=1 Voice Media
S1 Bearer
Service Data Flow Level
Radio Bearer
S5 Bearer
Application Level
Match All
S1 Bearer
Radio Bearer
S5 Bearer
SIP
RTP
TITLE: Quality of Service Identifier (QCI)
When a subscriber originates or answers a voice call a Dynamic Dedicated Bearer with a QCI of 1 is established. This Bearer carries the actual voice traffic. QCI 1 is used for conversational voice with low latency (less than 100 ms) and a packet loss of 1 in 100 packets. This makes voice service the highest priority.
Default Bearer for connectivity with the IMS PDN, QCI = 9. This is used for for IMS connectivity and signaling bearers to the PDN.
Default Bearer to carry IMS or SIP signaling, QCI = 5. This is used for SIP signaling, which is also a high priority. SIP signaling is very sensitive to packet loss and needs a higher priority to reduce call setup delay. IMS uses SIP signaling; at the start to trigger session initiation, and at the end to terminate a session. It does not have a guaranteed bit rate throughout the duration of the call.
Storyline: Bring in Dedicated Bearer when mentioned.

29. IMS Registration EPC IMS eUTRAN Terminating IMS LTE UE B party CSCF
CMS-8200
OpenTAS
MME
HSS AS
eUTRAN
eNodeB
PGW
LTE UE A party
SGW
CFX-5000
PCRF
P-CSCF
I-CSCF
S-CSCF
User Control
TITLE: IMS Registration
IMS Registration occurs after the LTE Attach, after the establishment of a Default Bearer, and after the discovery of a P-CSCF. The IMS authenticates and registers the UE as part of the IMS Registration. Let us take a closer look at this process.
Storyline: Automatically advance to next slide.

30. IMS Registration Process
Terminating IMS
IMS Registration Process
CSCF
EPC
IMS
CMS-8200
OpenTAS
MME AS
S6a/S13
HSS
eUTRAN Sh
S1-MME
S11 3
S6b
ISC 4
Sh/LDAP
eNodeB
PGW
S5/S8 6 Cx
S1-U
LTE UE A party
SGW 1 Gm
CFX-5000
LTE UE B party Gx Mw Mw Rx
PCRF
P-CSCF 2
I-CSCF
S-CSCF 5
User Control
TITLE: IMS Registration Process
Walk-through the IMS Registration process by clicking on the numbers in the slide.
Storyline: Following text will be displayed in pop-ups.
1 – After the initial LTE attach, Default Bearer creation, and P-CSCF discovery, the UE sends a SIP REGISTER request message to the P-CSCF over the Gm interface.
Storyline: Animate Gm interface UE > P-CSCF… moving SIP message through. 2 seconds pause.
2 – The P-CSCF forwards the REGISTER request to the I-CSCF, which forwards it to the S-CSCF using the Mw interface.
Storyline: Animate P-CSCF > I-CSCF >S-CSCF, moving message request from P- to I-CSCF, then to S-CSCF. 2 seconds pause.
3 – The S-CSCF authenticates the subscriber with the HSS over the Cx interface. The S-CSCF sends a message back to the I-CSCF, which forwards it on to the P-CSCF and then to the UE.
Storyline: Animate S-CSCF > HSS > S-CSCF > I-CSCF > P-CSCF > UE; message icon remains at S-CSCF while a dot moves to the HSS and back to the S-SCCF….then the message moves back down the line to the UE. 2 seconds pause.
4 – An Authentication response is then generated by the UE. The UE sends a REGISTER request message to the P-CSCF.
Storyline: Animate UE > P-CSCF; use mini message icon to represent messages. Move it from UE to P-CSCF. Same as before. 2 seconds pause.
5 – The REGISTER request is forwarded to the I-CSCF which sends the UE registration status with the REGISTER request to the S-CSCF.
Storyline: Animate P-CSCF > I-CSCF >S-CSCF; use mini message icon to represent messages. Move it from P-CSCF to I-, to S-. 2 seconds pause.
6 – The S-CSCF updates the subscriber profile in the HSS. The UE is now authenticated, and a response from the HSS is forwarded to the S-CSCF, to the I-CSCF, to the P-CSCF, and then back to the UE.
Storyline: Animate S-CSCF > HSS > S-CSCF > I-CSCF > P-CSCF > UE. Move mini message back down path to UE, then after 2 seconds, it disappears. Bring in green glare when UE is authenticated.

31. Final Assessment This slide does not contain narration.
Final Assessment questions appear in Storyline file.