IMS, VoLTE Seminar

8/20/2019 IMS, VoLTE Seminar

http://slidepdf.com/reader/full/ims-volte-seminar 1/137

Mike Keeley and Kurt Bantle

Spirent Communications

AN UP-CLOSE VIEW OFIMS, VOLTE & MEDIA SERVICES



2

Notices

The information contained in this presentation is considered to beconfidential and proprietary information of Spirent Communications, Inc.and is subject to the terms and conditions of the Non-disclosure

agreement (NDA) between the recipient(s) or recipient's organization andSpirent Communications, Inc.

All of the features, functionality and updates, and the timing of therelease of such features, functionality and updates presented, are for

informational purposes only and do not constitute a commitment,obligation or promise on the part of Spirent to provide such features,functionality and updates and are subject to change at Spirent’sdiscretion. At such time as these features and functionality may becomeavailable they must be purchased separately as a product or upgrade, or

in the case of updates, will be provided as part of a purchased AnnualSupport Agreement.



3

Spirent Communications Global Presence

A top 5 global telecom test company

~ half-billion dollar revenue (2010, USD)

Parent company: Spirent Communications plc

London Stock Exchange: SPT (FTSE 250)

More than 1,800 customersworldwide

Spirent Wireless:25 years in T&M

Network Emulation

Wireless Channel Emulation

Automated Test Systems

Conformance/Performance

Automated A-GPS Testing



4

Agenda

IMS in LTE Deployments

• The reasons for IMS

• IMS architecture & components• Session Initiation Protocol (SIP) messaging

The Killer Apps of 2012

• Evolution of Voice Services with LTE, including VoLTE

• Video Telephony

• Presence

Lunch (compliments of Spirent)

R&D Testing of IMS and Live Demonstrations



THE REASONS FOR IMS



Take Note!



7

Why IMS?



8

Technical History1999

Consortium focus group

Initially intended to bring anall-IP network to UMTS systems

At the time, this was intendedsolely for 3G (sic) wireless

Two main specifications:

Rel 5 - Initial 3GPP release was essentially handed to 3GPP bythe 3G.IP group

Rel 6 – Roaming, Public Service Identities, access-specific(i.e. GPRS-specific) issues are removed from core spec

Rel 7 – GRUU/presence – lets SIP address a specific user/UEcombination, Multi-media telephony (TAS or TelephonyApplicationServer) , MMS, support of CS users, Border control

(link multiple IP multimedia core networks or to link an IPmultimedia core network with another SIP-based multimedianetwork), Dynamic User Allocation (manages the use of AppServers by many subscribers), Wireline enhancements, Fixednetwork support (TISPAN)

Rel 8 – LTE, xDSL, Number portability, Introduction of 3GPP2 to

the spec, Preferred Circuit Carrier Access (long distance)

Rel 9 - Updated security (media plane), Updated emergency callcontrol, Updated MMTel

Rel 10 - Explicit Congestion Notification (ECN),Optimal media routing (OMR)

3G.IP

2011

3GPP Releases



9

Nominal Requirements

IMS can access information about:• the state of a user's connection, even while roaming

• user’s location, even while roaming

Multiple UEs per IMS service subscription (Public User Identity)

• But allowing the service to identify each UE

Voice transcoding (when two UEs do not support a common codec)

Access independence• Including access via any IP connection using Network Address Translation (NAT)

Interconnection between IMS domains (and different operators)

Negotiable and end-to-end QoS for real-time applications



IMS ARCHITECTURE& COMPONENTS



11

“IMS: It is too complicated!”

http://en.wikipedia.org/wiki/IP_Multimedia_Subsystem

IMS architecture can be complicated and difficultto understand when taken as a whole, but…

S - CSCFMGCF HSS

CxIMMGW

M n

Mb

Mg

MRFP

Mb

MbI-CSCF

Mw

Mw

Gm

MjMi

BGCF

Mk

C, D,Gc, Gr

UE

Mb

Mb

Mb SLF

Dx

Mp

CS

CS

IMS Subsystem

Cx

AS

ISC

Sh

Ut

BGCF

Mg

Dh

Ma

P-CSCF

Mx

Mx

Mx

CS Network Mm

Legacy mobilesignalling NetworksMk Mm

TrGW

IP Multimedia Networks

IBCF

Ix

IciIzi

MRBRc

ISC

Mr

MRFC

Cr

TS 23.228 IP Multimedia Subsystem (IMS); Stage 2 (Release 8)

Figure 4.0: Reference Architecture of the IP Multimedia Core Network Subsystem



12

IMS Architecture – Breaking it Into Pieces

Consider IMS as it relates to just your home LTE network

• Remove mobility with visiting networks, legacy networks (3G, 2G), non-cellularnetworks (WiFi, Cable/DSL)

STEP 1

Split the IMS architecture into its major building blocks

• User equipment (UE): The endpoint of the IMS architecture that residues with the user.Contains a SIP user agent

• Transpor t : This is the portion of the IMS architecture through which the overallnetwork is accessed (e.g. LTE Evolved Packet System), including the Access Network

• Control : Includes the IMS Core. Provides session and media control

• Appl icat ion: Contains the Application Servers that host the IMS services

STEP 2



13

UICC (Universal Integrated Circuit Card)

• A smart card that contains one or more applications

• GSM SIM (Subscriber Identity Module)

• UMTS/LTE USIM

• CDMA CSIM

• IMS ISIM (IP Multimedia Services Identity Module)

• ISIM contains:

- IPMI (IP Multimedia Private Identity) – Permanently allocated global identity assigned by

a user’s home operator

- The home operator’s domain name

- IMPU (IP Multimedia Public Identity) – Used to request communication with another user

• A device may have multiple IMPUs, and multiple devices may share an IMPU

- URI (Uniform Resource Identifier) – A user’s “SIP phone number”

• Resembles an email address in appearance (sip:<username>@<host>:<port>)

- A long-term secret to authenticate and calculate cipher keys

User Equipment

UE



14

User Equipment

SIP UA (SIP User Agent)

• The logical end-point of a SIP network

• Creates and receives SIP messaging• Manages a SIP session

• Can perform two roles:

• UAC (User Agent Client) – Sends SIP requests

• UAS (User Agent Server) – Received requests and sends SIP responses

• An example of a SIP UA is a SIP phone providing typical telephonefunctionality

• Dial, answer, reject, hold, transfer

UE



15

PDN Gateway (Public Data Network Gateway)

• Provides access for the UE to external packet data networks

• Can be multiple gateways for access to multiple PDNs (e.g. Internet, IMS)

• Anchor for mobility between LTE and other non-3GPP technologies

EPCE-UTRAN IP Services

Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi

LTE Evolved Packet System



16

PCRF (Policy and Charging Rules Function)

• Provides real-time determination of whether traffic should be allowed(Policies) and how to account for traffic (Charging Rules)

• Initiates appropriate bearers within the packet core based on the IMSservice requested



Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



17

IMS Core (Control Layer)

CSCF (Call Session Control Function)

• Establishes, monitors, supports and releases multimedia sessions

• Manages the user’s service interactions

• Can consist of three different entities:


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



18


Serving (S-CSCF)

• Controls the communication session

• Interfaces with the applicable Applications Servers

• Is located in the user’s home network


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



19


Proxy (P-CSCF)

• Provides the initial contact point for the SIP User Agent (UE)

Handles all of the requests to/from the user and forwards them asappropriate

• Optionally can include a PCF (Policy Control Function) to managemedia QoS


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



20


Interrogating (I-CSCF)

• Provides a gateway to other domains (e.g. when a message or servicemust traverse multiple IMS domains)


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



21


HSS (Home Subscriber Server)

• Securely stores user profile information

• S-CSCF uses Diameter protocol to access HSS


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



22


SLF (Subscriber Location Function)

• Identifies which HSS contains the user’s profile if multiple HSS are in use


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



23


MGCF (Media Gateway Control Function)

• Controls the various Media Gateways (MGW)

Media Gateways send and receive media over PS or CS protocols

Can convert between different Codecs (AMR vs. G.711)

For CS networks, converts between RTP and PCM

• Does protocol conversion between SIP and ISUP/BICC


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



24


BGCF (Breakout Gateway Control Function)

• Provides the breakout to circuit-switch domain, if necessary

• Could be via selecting the MGCF in the same network, a MGCF in anotherIMS network, or via MGW when the other network is not IMS-based


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



25


SGW (Signaling Gateway)

• Interfaces with the signaling plane of Circuit Switched (CS) networks


Internet

IMSNetwork

eNode B

eNode B

eNode BInternet PDN

IMS PDN S7

S6c

S5

S11

S6a Wx

LTE-Uu

S1-U

S1-

MME

Rx

SGi



26

The Protocols of IMS

Session Initiation Protocol (SIP)

SigComp

Real-time Transport Protocol (RTP)

RTP Control Protocol (RTCP)

IPSec

Diameter• Provides Authentication and Authorization functions between entities in the

Packet and IMS cores



27

How SIP Stacks Up

SIP is not dependent on the underlying protocols

Physical

Data Link

IP

TCP/UDP



28

Session Initiation Protocol (SIP)

Basic SIP defined in RFC 3261

• Used to create, modify and terminate multimedia sessions

• Key function is to deliver session description information to the user at their

current location using SDP• Text-based protocol (easy to debug); Client/Server (Request/Response)

• Based on familiar protocols such as HTTP and SMTP

SIP for IMS is “SIP on Steroids” with many extensions for 3GPPsupport

• Binding of SIP public URI to UE’s IP address/host name during REGISTRATION

• Support for instant messages and handling of subscription events



29

SIP Requests

SIP Requests have the format:

<request start line><request headers> (several lines)<blank line><message body>(carries the SDP message)



30

SIP Requests

SIP Requests always begin with a Method (type of request) andthe URI where the Response should be sent

SIP RequestMethod Name Description

Definedin

INVITE Indicates a client is being invited to participate in a call session RFC 3261

ACK Confirms that the client has received a final response to an INVITE request RFC 3261

BYE Terminates a call and can be sent by either the caller or the callee RFC 3261

CANCEL Cancels any pending request RFC 3261

OPTIONS Queries the capabilities of servers RFC 3261REGISTER Registers the address listed in the To header field with a SIP server RFC 3261

PRACK Provisional acknowledgement RFC 3262

SUBSCRIBE Subscribes for an Event of Notification from the Notifier RFC 3265

NOTIFY Notify the subscriber of a new Event RFC 3265

PUBLISH Publishes an event to the Server RFC 3903

INFO Sends mid-session information that does not modify the session state RFC 6086REFER Asks recipient to issue SIP request (call transfer) RFC 3515

MESSAGE Transports instant messages using SIP RFC 3428

UPDATE Modifies the state of a session without changing the state of the dialog RFC 3311



31

SDP – Session Description Protocol

Defined in RFC 2327 SDP is a textual format used to describemultimedia sessions. A session description contains enoughinformation for the remote user to join the multimedia session

SDP Offer/Answer model (RFC 3264) provides a two-way sessiondescription exchange or negotiation

• Offering user sends a session description (the Offer), the remote usergenerates a new session description (the Answer) and sends it to the offeringuser

• The Offer/Answer exchange provides both users with a common view of themultimedia session – at a minimum media formats and transport addresses

• Other information can be exchanged too – e.g. cryptographic keys andalgorithms



32

SIP Responses

SIP Responses have the format:

<response status line><request headers> (several lines)<blank line>

<message body>



33

SIP Responses

SIP Responses always begin with a Response Code, which falls into one of thefollowing categories:

• Informational/Provisional (1xx): Request received and being processed

• 100 Trying, 180 Ringing

• Successful (2xx): The action was successfully received, understood, and accepted

• 200 OK, 202 Accepted

• Redirection (3xx): Further action needs to be taken (typically by sender) to complete the request

• 301 Moved Permanently, 302 Moved Temporarily

• Client Failure (4xx): The request contains bad syntax or cannot be fulfilled at the server

• 401 Unauthorized, 403 Forbidden

• Server Failure (5xx): The server failed to fulfill an apparently valid request

• 500 Server Internal Error, 504 Server Time-out

• Global Failure (6xx): The request cannot be fulfilled at any server

• 600 Busy Everywhere, 604 Does Not Exist Anywhere



34

SigComp (Signaling Compression)

Compression method for text-based signaling (such as SIP)

Reduces the time needed to transport SIP messaging

SigComp is used between the device and the P-CSCF

IMS device can use DEFLATE (preferred) or LZSS compressionalgorithm

Current status:

• SigComp is not being usedfor SMS-only IMS devices

• Other IMS devices (e.g. VoLTE)shall use SigComp for all SIP

messaging over any data link



35

RTP Port n (even-numbered port)

RTCP (Control) Port n + 1

RTP / RTCP

Real-time Transport Protocol and RTP Control Protocol workhand-in-hand

• RTP (the data transfer protocol) defines a standardized packet format fordelivering audio and video over IP networks

• RTCP (the control protocol) is used to monitor transmission statistics andquality of service (QoS), and aids synchronization of multiple streams

• RTCP is optional for VoLTE implementations

RFC 3550 RTP: A Transport Protocol for Real-time Applications



36

Key Management

Security in IMS Networks

Diffie-Hellman Public-Key Algorithm

Invented by Whitfield Diffie and MartinHellman in 1976 Published in an article“New directions in Cryptography.”First public key ever developed.

Need to provide: Authentication and Integrity Protection

Encryption

Authentication



37

IMS Authentication

IMS clients are challenged at various points by the network

• Initial registration, De-registration, certain session requests (e.g. SIP INVITE)

IMS AKA (Authentication and Key Agreement) method is used for

authentication (with IPsec)• AKA provides mutual authentication



38

IMS Authentication

Shared Secret Data (SSD)Stored at UE (e.g. I-SIM)Shared Secret Data (SSD)Stored at UE (e.g. I-SIM)

Shared Secret Data (SSD)Stored at Network (e.g. HSS)

Shared Secret Data (SSD)Stored at Network (e.g. HSS)

Calculate “response”using MD5 (SSD + nonce)

Calculate “response”using MD5 (SSD + nonce)

Calculate expected“response”

using MD5 (SSD + nonce)

Calculate expected“response”

using MD5 (SSD + nonce)

Compare expected andactual “response” valuesCompare expected and

actual “response” values

UE Network



SESSION INITIATION PROTOCOL(SIP) MESSAGING



40

SIP (IMS) Registration - Roles

The UE initiates a Registration sequence

• Attach and PDP context activation

• Unauthenticated registration attempt

• IPSec Security Association establishment

• Authenticated registration (assuming network challenges)

The P-CSCF typically resides in the visited network and acts as the

UE's gateway into the UE's home network• Identifies the home IMS network

• Routes traffic to and from the home IMS network

• Establishes the IPSec security association



41

SIP (IMS) Registration - Roles

The I-CSCF typically resides in the home network and acts as thefront-end of the Home IMS

• Interfaces with the P-CSCF in the visited network

• Selects the S-CSCF by querying the HSS

The S-CSCF typically resides in the home network

• Handling the registration request from the I-CSCF

• Pulling the authentication vectors from the HSS

• Passing the authentication vectors to the P-CSCF via the I-CSCF

• Authenticate the user in the second registration attempt



42

EPS Attach and P-CSCF Discovery

UE must first complete EPS Attach, establish EPS bearercontext and discover which P-CSCF(s) to use



43


After RRC Connection is established, UE does an ATTACHREQUEST message and includes a PDN CONNECTIVITY REQUESTmessage



44


After RRC Connection is established, UE does an ATTACHREQUEST message and includes a PDN CONNECTIVITY REQUESTmessage

PDN Connectivity

Request containsProtocol ConfigurationOptions IE with

request for P-CSCFaddress



45


UE must first complete EPS Attach, establish EPS bearercontext and discover which P-CSCF(s) to use

EPS A h d P CSCF Di



46


After Authentication, Security and UE Capability requests,network accepts Attach and activates EPS bearer context

EPS Att h d P CSCF Di



47


After Authentication, Security and UE Capability requests,network accepts Attach and activates EPS bearer context

IMS PDN

One or more P-CSCF IPaddresses provided




48


Internet

eNode B

eNode B

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

LTE Evolved Packet SystemMobi l e Net wor k At t ach –Def aul t Int er net Bear er

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

Authenticate UE

S5

S5

VoLTE Call Example



49


Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

VoLTE Call ExampleMobi l e Net wor k At t ach –Def aul t Int er net Bear er

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

Control Signaling to Create Default Bearer

S5

VoLTE Call Example



50


Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

VoLTE Call ExampleMobi l e Net wor k At t ach –Def aul t Int er net Bear er

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

Default Internet Bearer

S5

IMS Initial Registration and Registration Event



51

g gPackage Subscription

UE Attach ProcedureAttach Procedure Network



52




53

Package Subscription




54




55





56

IMS Initial Registration and Registration Eventk b



57



UE hascompletedinitial IMS

registration



58

VoLTE Call Example



59


Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

Mobi le Net wor k At t ach –Def aul t IMS Signal i ng Bear er

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

Control Message to create Default IMS signaling Bearer

VoLTE Call ExampleM bi l N k A h D f l IMS Si l i B



60


Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

Mobi le Net wor k At t ach –Def aul t IMS Signal i ng Bear er

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

Default IMS Signaling Bearer

VoLTE Call ExampleIMS R i t t i i SIP Si l i



61


Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

IMS Regi st r at i on v i a SIP Signal i ng

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

IMS Registration

IMS authenticates, learns UE features

IMS Initial Registration and Registration EventPackage Subscription



62


registration





63




64


registration





65




66


registration





67




68


registration



UE hascompleted

subscriptionto the

registrationevent

package



69

VoLTE Call ExampleSubscr i be t o Reg Event Package



70


Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

Subsc be o eg e ac age

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

Subscribe to Reg Event Package

SMS



71

Mobile-Originated SMS

UE IMS Registration ProcedureIMS Registration Procedure Network



72

SMS



73





74

SMS



75

Mobile-Terminated SMS





76

SMS



77

Mobile-Terminated SMS





78



THE KILLER APPS OF 2012

IMS Applications - Vision



80

Telephony Services Other CommunicationsServices Other Services

Residential VoIP Push-to-Talk over Cellular Desktop sharing & collaboration

PSTN telephony emulation Push-to-X Gaming with voice/messaging

Multimedia residential telephony POC with multimedia conferencing Mobility management

Business telephony Instant messaging & presence Enhanced IPTV

IP Centrex Converged or unified messaging Enhanced ringtone downloads

Hosted PBX Videoconferencing &videotelephony

Mobile advertising & marketing

Voice call continuity Video messaging Gambling & betting

One-number phone services Call and share Multimedia roaming

Web-based telephony Location-based services Mobile content delivery

Enhanced voicemail Parental or privacy controls

Active phone book,presence-enabled address group

IMS Applications - Current



81

Multiple IMS applications are actively being developed and/ordeployed on UEs now

• Registrations

• SMS• Voice over IP over IMS (aka VoLTE)

• Video Telephony

• Presence



EVOLUTION OF VOICESERVICES WITH LTE

Evolution of Voice Services with LTE Networks



83

2011 2012 2013

CDMALegacy

SVLTEVoLTE +

1X CS

LTE-only

Voice Devices

UMTSLegacy

SRVCCVoLTECSFB

SVLTE – Simultaneous Voice and LTE



84

Uses two radios to simultaneous communicate with:

• 1X network for services such as CS Voice, SMS, Emergency Services

• LTE network for high-rate PS data services

Pros

• Rapid deployment – Reuses well established methods for CS voice

• High-quality concurrent services

Cons• Cost of two radios

• Cross-radio, Cross-band interaction andinterference

• Maximum allowable output powerconsiderations

• Battery life considerations

CSFB – Circuit Switched Fallback



85

When CS services (voice, SMS) are needed, provides a mechanism tomove from LTE to UMTS/GSM (or even 1X)

Pros

• Allows for single radio(or dual receiver) design

• Complete CS services andfeatures

• Primarily operating inLTE mode

Cons

• PS services are degraded on the

slower legacy PS network• Depending on type of CSFB used,

PS bearers will be interrupted

• Longer call setup times (≈ 500ms)?

Multiple Options for CSFB



86

For MT services, UE is notified of need for CS services with CS SERVICENOTIFICATION message

UE responds with EXTENDED SERVICE REQUEST message

E-UTRAN directs UE to 2G/3G network:Destination RAT Option 3GPP Release

UMTS RRC Connection Release with Redirection (w/o Sys Info) Release 8

UMTS RRC Connection Release with Redirection (w/ Sys Info) Release 9

UMTS PS Handover with DRBs Release 8

GSM RRC Connection Release with Redirection (w/o Sys Info) Release 8

GSM RRC Connection Release with Redirection (w/ Sys Info) Release 9

GSM PS Handover with DRBs Release 8

GSM Cell Change Order (w/o NACC) Release 8

GSM Cell Change Order (w/ NACC) Release 8

SRVCC – Single Radio Voice Call Continuity



87

Allows a PS/IMS-based (VoLTE) Voice Call on LTE to transition to alegacy CS network

Pros

• Utilizes a single radio• Provides ubiquitous voice coverage without 100% LTE coverage

Cons

• Due to complicated signaling, possible

brief break in audio• Additional client support for SRVCC

VoLTE – Voice over LTE

GSM A i i P R f D IR 92 id fil



88

GSM Association Permanent Reference Document IR.92 provides a profileof minimum mandatory 3GPP capabilities to ensure interoperable SIP-based IMS VoIP and SMS for User Equipment and the LTE EPC

• IMS basic capabilities and supplementary services for telephony

• Real-time media negotiation, transport and codecs• LTE radio and ePC capabilities

• Functionality that is relevant across the protocol stack and subsystems

GSMA IR.88 LTE Roaming Guidelines provides guidance for LTE roaming

scenarios

Mobile Device

LTEwith VoIP optimizations

Bearers/QoS RoHC

TCP/IP – UDP/IP

SIPHTTP/XCAP RTP/RTCP

SupplServices

Codecs

Radio & Access Network

LTEwith VoIP optimizations

Bearers/QoS RoHC

TCP/IP – UDP/IP

Servers (IMS)

TCP/IP – UDP/IP

SIPHTTP/XCAP RTP/RTCP

SupplServices

Codecs

Requirements to Support VoLTE

LTE RAN f t



89

LTE RAN features• Semi-Persistent Scheduling

• Transmission Time Interval (TTI) Bundling

• Discontinuous Reception (DRX)• Robust Header Compression (RoHC)

QoS

• Multiple Bearers (Default, Dedicated)• QoS Class Identifiers (QCIs)

IMS

• SIP, SDP, RTP, RTCP, IPSec

Codecs

• Adaptive Multi-Rate (AMR), Wideband AMR (AMR-WB), EVRC

Semi-Persistent Scheduling (SPS)

I LTE DL d UL ffi h l d i ll h d

ISSUE



90

When to use SPS? Look at QCI and Bearer type

In LTE, DL and UL traffic channels are dynamically shared

• Control channel (PDCCH) must be used to identify which subframes a user should decodeon the downlink (PDSCH), and which users are allowed to transmit in each UL subframe(PUSCH)

• Every physical resource block (PRB) on DL and UL must be granted

• Grant control channel overhead too great for persistent allocations of small packets(consistent with VoIP characteristics)

Define a transmission pattern and “permanently” assign PRBs based on that pattern

• Ex: Voice = 1 coded packet every 20ms

• During silent period, PRB assignment can be canceled

• UL can be implicitly canceled after a defined number of empty UL transmissions

• DL can be canceled with an RRC message

SOLUTION

Transmission Time Interval (TTI) Bundling

Sh t (1 ) TTI i t d d i LTE t d d t d l t

ISSUE



91

Same process to configure normal HARQoperation (Radio Resource Control (RRC) protocol)

is used to configure TTI bundles

Short (1ms) TTI introduced in LTE to reduce end-to-end latency

• At cell edges, UE might not have enough power available to reliably deliver an entireVoIP packet in one TTI

Bundle multiple TTIs together without waiting for HARQ feedback

• Send VoIP packet as a single PDU during a bundle of subsequent TTIs

• HARQ feedback is only expected after the last transmission of the bundle

SOLUTION

Discontinuous Reception (DRX)

Constant voice session can more quickly reduce battery life

ISSUE



92

RRC must carefully configure DRXto account for application’s latencyand responsiveness requirements

Constant voice session can more quickly reduce battery life

VoLTE traffic is highly predictable (e.g. 20ms codec packets) – UE receiver does not have to

constantly monitor the PDCCH

SOLUTION

Robust Header Compression (RoHC)

IP header information can be disproportionately large compared to the relatively small

ISSUE



93

IP header information can be disproportionately large compared to the relatively smallVoLTE codec packets being transmitted large air interface bandwidth inefficiency

• RTP/UDP/IP header can be ~40 to 60 bytes long

• AMR-WB @ 20msec = ~50 bytes/frame

Compress and decompress the collection of headers (RTP/UDP/IP) before and after the air

interface

• Reduce header info to ~ 2 to 4 bytes

SOLUTION

IP

UDP

RTP

IP

UDP

RTP

ROHC

C/D

ROHC

IP

UDP

RTPD/C

IP

UDP

RTP

Internet Link Air Interface Internet Link

Audio/Video Application Audio/Video Application

RoHC Node RoHC Node

Simplified VoLTE Call Flow

Initial attach



94

Initial attach• Create default bearer for IP connectivity

• Discover P-CSCF

Create default bearer for SIP signaling

• Register UE with IMS network

• Subscribe to Registration event package

<ready to place & receive calls>

Send SIP INVITE

• SDP Offer/Answer media negotiation

• Create dedicated bearer for RTP data

• <talk>

Terminate Call

UE1 UE2CSCF

VoLTE Call Flow – UE-Initiated Call



95

IMS RegistrationIMS Registration



96

More about theSIP INVITE SDP



97

Field Meaning Format

v= version v=0

o= session owner & ID o=<username> <session id> <version> <network type><address type> <address>

s= session name s=<session name>t= time the session is

activet=<start time> <stop time>

m= media type, format andtransport address

m=<media> <port> <transport> <format list>

<media> is “audio” or “video” (two m= lines for both)c= connection information c=<network type> <address type> <connection address>

a= session attributes a=<attribute> or a=<attribute> <value>


(session attributes)



98

(session attributes)

Session Attribute Format and Description

rtpmap a=rtpmap:<payload type> <encoding name>/<clock rate>[/<encoding parameters>]

Mapping from RTP payload codes (from the <format list> in the“m=“ field) to a codec name, clock rate and other encoding

parameters

sendrecv a=sendrecv (or “sendonly”, “recvonly”, “inactive”, “broadcast”)

ptime a=ptime:<packet time>

Length (in ms) carried in one RTP packet

fmtp a=fmtp:<format> <format specific parameters>

Defines parameters that are specific to a given format code


(rtpmap and fmtp



99

(rtpmap and fmtpsamples)

PayloadType Encoding Name Sample Usage

0 PCMU a=rtpmap:0 PCMU/8000

8 PCMA a=rtpmap:8 PCMA/8000

100 Telephone Event a=rtpmap:100 telephone-event/8000

a=fmtp:100 0-15

102 AMR (Adaptive Multi-Rate)

a=rtpmap:102 AMR/8000a=fmtp:102 octet-align=1; modeset=0,2,5,7;mode-change-capability=2

104 AMR-WB (AMR Wideband) a=rtpmap:104 AMR-WB/16000

a=fmtp:104 octet-align=1; modeset=0,2,5,7;mode-change-capability=2


UE1 UE2CSCF



100




101


UE1 UE2CSCF



102

RTP Voice Traffic




103


VoLTE Call ExampleUE usi ng Int ernet , No act i ve Voi ce Cal l

C



104

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

UE using Internet


VoLTE Call ExampleIn i t i at e Voice Cal l

Cx



105

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

Initiate Phone Call (Sip Signaling)



Cx



106

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

IMS requests Dedicated Bearer for RTP Voice (QCI=1)

QCI (QoS Class Identifier) Values for Bearers

QCI ResourceType

Priority Packet DelayBudget (ms)

Packet ErrorLoss Rate

Example Services



107

Type Budget (ms) Loss Rate

1 GBR 2 100 10-2 Conversational Voice

2 GBR 4 150 10-3 Conversational Video (live streaming)

3 GBR 5 300 10-6 Non-conversational video (bufferedstreaming)

4 GBR 3 50 10-3 Real-time gaming

5 Non-GBR 1 100 10-6 IMS Signaling

6 Non-GBR 7 100 10-3 Voice, Video (live streaming),interactive gaming

7 Non-GBR 6 300 10-6 Video (buffered streaming)

8 Non-GBR 8 300 10-6 TCP-based (WWW, email, FTP)

9 Non-GBR 9 300 10-6

GBR = Guaranteed Bit Rate



Cx



108

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

IMS

Rx

Gx

ISC

Sh

Cx

S6b

SWx

S5

PCRF Triggers Network Initiated Dedicated Bearer

Voice Data


VoLTE Call ExampleIni t i at e Voice Cal l , Dedicat ed Bearer Est abl i shed f or Voice

Cx



109

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi

IMS

Rx

Gx

ISC

Sh

S6b

SWx

S5

RTP Dedicated Bearer for RTP Voice

Voice Data

SGi/Gm


VoLTE Call ExampleVoi ce Conversat i on

Cx



110

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

Voice Data

SGi

IMS

Rx

Gx

ISC

Sh

S6b

SWx

S5

Voice Traffic in Dedicated Bearer

SIP Signaling Traffic in Default Bearer

SGi/Gm

VoLTE Call Flow – UE-Initiated Call Termination

UE1 UE2

CSCF



111

Existing call between UE1 & UE2Existing call between UE1 & UE2


VoLTE Call ExampleTerminat e Cal l

Cx



112

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi

IMS

Rx

Gx

ISC

Sh

S6b

SWx

S5

SIP Signaling – Terminate Call

Voice Data

SGi/Gm


VoLTE Call ExampleTerminat e Cal l

Cx



113

Internet

eNode B

eNode B

S5S11

S6a

LTE-Uu

S1-U

S1-MME

SGi

IMS

Rx

Gx

ISC

Sh

S6b

SWx

S5

Delete Dedicated Bearer Messaging

Voice Data

SGi/Gm


VoLTE Call ExampleNo Voice Call, Dedicated Bearer Deleted

IMS

Cx



114

Internet

eNode B

eNode B

S5

S11

S6a

LTE-Uu

S1-U

S1-MME

SGi/Gm

SGi

IMS

Rx

Gx

ISC

Sh

S6b

SWx

S5

Attached, No Voice Call, No Data

Voice Data

Supplementary Services with VoLTE

Call Waiting

C ll H ld



115

Call Hold

3-way Conferencing

Call Forking(Simultaneous Ringing)

UE1 UE2

Existing call between UE1 & UE2

Existing call between UE1 & UE2

UE3

CSCF

INVITE (UE3 to UE1)

180 RINGING

INVITE (UE3 to UE1)

UE1 isnotifiedof incoming1



116

180 RINGINGof incomingcall fromUE3

UE2 isplaced onhold

Call iscompletedbetween

UE1 andUE3

PRACK/200 OK Exchange

reINVITE (UE1 to UE2)(SDP, a = SendOnly)

200 OK

ACK (UE1 to UE2)

200 OK (UE1 to UE3)

ACK

reINVITE (UE1 to UE2)(SDP, a = SendOnly)

200 OK (UE2 to UE1)(SDP, a = RecvOnly)

ACK (UE1 to UE2)

200 OK (UE1 to UE3)

ACK

1 User is presented with option to answer waiting call or not

2 User chooses to answer waiting call and puts existing call on hold

3 UE1 completes call setup with UE3

1

2

3

Video Telephony

Adds a 2nd IMS

Dedicated Bearer forvideo traffic (QCI=6)



117

( )

New scenarios:

• Video call “upgrade”(add video to an existing VoLTE call)

• Video call “downgrade”(drop video and go to VoLTE call)

SIP reINVITE is used to triggerupgrade or downgrade

• New SDP offer contents

RRCConnectionConfiguration usedto activate or deactivate dedicatedbearer

Presence

Allows a user to subscribe to “presence” information about its

contacts• If the contact accepts the request the user will be notified when presence



118

If the contact accepts the request, the user will be notified when presenceinformation about the contact is published (changes)

Watcher PS Presentity CSCFWatcher CSCF

SUBSCRIBEEvent=presence,

Request URI = Presentity URI

SUBSCRIBE

NOTIFY

200 OK

Presentity UE

200 OK

NOTIFY

200 OK NOTIFY

NOTIFY

200 OK

200 OK

200 OK

200 OK

PUBLISH

Watcher is authorized

Publisher is authorized

SUBSCRIBE

PUBLISH



R&D Testing of IMS

VoLTE Testing Methodologies

Interoperability – Protocol Analysis

• SIP, SDP



120

• Registrations, Authentication, Addressing,Calls, Supplementary Services

• Feature Interaction

Mobility

Quality of Experience (QoE) – Voice Quality

• MOS-LQ (Listening Quality) (e.g. PESQ, POLQA)

Quality of Service (QoS) – Measuring KPIs

• One-way delay, Packet loss rate, Packet lossdistribution, One-way delay variation, data rate

IMS Testing Plans

GSM Association

IR 92 IMS Profile for Voice and SMS



121

IR.92 IMS Profile for Voice and SMS

• Defines a minimum mandatory set offeatures that a UE and network arerequired to implement to guaranteeLTE IMS interoperability and quality

• ~ 40 test scenarioscan be derived

from therequirements

IMS Testing Plans

The International Multimedia Telecommunications Consortium

Test Cases – IMS Profile for Voice and SMS



122

Test Cases IMS Profile for Voice and SMS

• ~ 30 test cases designed toverify an IMS Client Applications’ability to interoperate withIMS network implementations

Standards-developed Conformance Test Specifications

3GPP TS 34 229-1

IMS Testing Plans



123

3GPP TS 34.229 1

• Internet Protocol (IP) multimedia call control protocol based on

Session Initiation Protocol (SIP) and Session Description Protocol (SDP);User Equipment (UE) conformance specification;Part 1: Protocol conformance specification

IMS Testing Plans

Carrier-developed Conformance Test Specifications

E g Verizon Wireless Device Compliance Test Plan – LTE SMS



124

E.g. Verizon Wireless Device Compliance Test Plan LTE SMS

POLQA - voice quality analysis of HD Voice for 3G and 4G/LTEnetworks

Audio Quality Testing



125

Latency, jitter (variable delay), gain variations, speech signal andBGN level measurements, level clipping, dropouts (e.g. generated

by packet loss), operability of VAD

Handset, Headset, Speaker modes

2000 2005 2010

VoIP 3G 3.5G NGN UC 4G/LTE

PESQ ITU-T P.862

02/2001

PESQ-WBP.862.2

11/2005

POLQAP.8632011

P O T S

H D

V o i c e

Narrow-band (NB)3.4 kHz

Wide-band (WB)7 kHz

Super-wide-band (SWB)14 kHz

Evolution of ITU-T Recommendations for Voice Quality Testing(P.86x – Full Reference MOS-LQO)

Summary

IMS has been around for > 10 years, but it is nowbecoming a reality

IMS provides convergence on multiple fronts Access-type (fixed, mobile)



126

IMS provides convergence on multiple fronts Access type (fixed, mobile)

IMS offers operators the chance to add value to IP-based services by

becoming service administrators While IMS can be broken into manageable pieces, it still introduces

multiple new protocols and procedures

Killer IMS applications are rapidly reaching commercial maturity

• SMS, Voice, Video, etc.

Test plans and testing of IMS in cellular environments is starting



LIVE DEMONSTRATION

CS8: For All Phases of Device Development



128

PLATFORMVALIDATION

• RF Performance inPlatforms/Handset

• Protocol customizationfor regions

• Service Interaction

tests i.e. Voice + Data,Voice + SMS etc.

SYSTEM &APPLICATION TEST

• End-to-End testing withFading/Noise

• System Test underMulti-Cell testenvironment

• Adversarial DataTesting

• Real IPv6 with UE-to-Server Connectivity

RF/BASEBANDDEVELOPMENT &INTEGRATION• L1-only BB testing• Parametric testing• Protocol testing

RADIO PROTOCOLDEVELOPMENT

• Protocol design• Protocol testing• Adversarial testing

CS8 for Protocol Testing

Interactive GUI for intuitive testing (no scripting required)

Data testing (data throughput, data retry)



129

Multi-RAT network emulation

• LTE, WCDMA, HSDPA, CDMA, EV-DO

Real-time responses from network-grade protocol engine


The industry’s most complete and realistic Evolved Packet Core(EPC)

• The same EPC emulation used to test infrastructure products



130

p

True IPv6 network emulation

• (not just IPv6 headers!)

• UE-to-Server Connectivity


Interactive UI for intuitive LTE performance testing for• Data throughput

• Data retry



131

• Data retry

• Inter-RAT handovers

Protocol testing• Simulate end-to-end tests for Protocol Rejects and Negative responses

CS8 for Adversarial Protocol (NAS/RRC)



132

• Data Retry protocol tests

Demonstration Scenario

Done in Field Done in Office / Lab



133

Drive test LTE USBdongle on VZW liveLTE Network

QXDM Log file

Output IPv6 flowfrom QXDM toWireshark PCAP file

PCAP file

Import PCAP file intoSpirent CS8’s IMSCall Flow Editor

CS8 Data MessageFlow file

Recreate drive test

scenario usingSpirent’s CS8eAirAccess

Edit CS8 Data

Message Flow file tocreate an alternate

scenario

Modified / NewCS8 Data Message

Flow file

Use Spirent’s CS8

eAirAccess toexecute Modified /New IMS test

scenario



QUESTIONS?



THANK YOU!



SOURCES

SourcesGraham Finnie. IMS Application Servers & the IMS Applications Environment. Retrieved November 8, 2011 fromhttp://www.heavyreading.com/details.asp?sku_id=1399&skuitem_itemid=984

Jhansi Jujjuru. AN OVERVIEW OF INTERNET PROTOCOL MULTIMEDIA SUBSYSTEMS (IMS) ARCHITECTURE . Retrieved November 8, 2011 fromhttp://www.rivier.edu/journal/ROAJ-Spring-2008/J134-Jujjuru.pdf

IETF. RFC4566. Retrieved November 8, 2011 from http://www.ietf.org/rfc/rfc4566.txt

Hill Associates Breakout gateway control function Retrieved November 15 2011 from http://wiki hill com/wiki/index php?title=BGCF



137

Hill Associates. Breakout gateway control function. Retrieved November 15, 2011 from http://wiki.hill.com/wiki/index.php?title=BGCF

Gilles Bertrand. The IP Multimedia Subsystem in Next Generation Networks. Retrieved November 8, 2011 fromhttp://www.tele.pw.edu.pl/~mareks/auims/IMS_an_overview-1.pdf

Wikipedia. IP Multimedia Subsystem. Retrieved November 8, 2011 from http://en.wikipedia.org/wiki/IP_Multimedia_Subsystem

Wikipedia. Session Initiation Protocol. Retrieved November 8, 2011 from http://en.wikipedia.org/wiki/Session_Initiation_Protocol

Radio-Electronics. IMS, IP Multimedia Subsystem tutorial. Retrieved November 8, 2011 from http://www.radio-electronics.com/info/telecommunications_networks/ims-ip-multimedia-subsystem/tutorial-basics.php

Wikipedia. IP Multimedia Services Identity Module. Retrieved November 15, 2011 from

http://en.wikipedia.org/wiki/IP_Multimedia_Services_Identity_Module

Verizon Wireless. DEVICE COMPLIANCE TEST PLAN - LTE SMS, Version 6.0 . Issued March 2011. Retrieved November 15, 2011 fromhttp://opennetwork.verizonwireless.com/getDeviceCertified_docSpec.aspx

Wikipedia. Signaling Compression. Retrieved November 15, 2011 from http://en.wikipedia.org/wiki/Signaling_Compression

Vladimír Toncar. VoIP Protocols: SIP Call Flow . Retrieved November 22, 2011 fromhttp://toncar.cz/Tutorials/VoIP/VoIP_Protocols_SIP_Call_Flow.html

EventHelix. IMS Registration Sequence Diagrams. Retrieved November 30, 2011 from http://eventhelix.com/ims/registration/

Wikipedia. Real-time Transport Protocol. Retrieved November 30, 2011 from http://en.wikipedia.org/wiki/Real-time_Transport_Protocol

IMS, VoLTE Seminar

Documents

Transcript of IMS, VoLTE Seminar