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Transcript of IMS, VoLTE Seminar
8/20/2019 IMS, VoLTE Seminar
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Mike Keeley and Kurt Bantle
Spirent Communications
AN UP-CLOSE VIEW OFIMS, VOLTE & MEDIA SERVICES
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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.
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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
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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
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THE REASONS FOR IMS
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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
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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
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IMS ARCHITECTURE& COMPONENTS
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“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…
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Figure 4.0: Reference Architecture of the IP Multimedia Core Network Subsystem
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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
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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
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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
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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
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LTE Evolved Packet System
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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
LTE Evolved Packet System
EPCE-UTRAN IP Services
Internet
IMSNetwork
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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:
EPCE-UTRAN IP Services
Internet
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IMS Core (Control Layer)
Serving (S-CSCF)
• Controls the communication session
• Interfaces with the applicable Applications Servers
• Is located in the user’s home network
EPCE-UTRAN IP Services
Internet
IMSNetwork
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IMS PDN S7
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LTE-Uu
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IMS Core (Control Layer)
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
EPCE-UTRAN IP Services
Internet
IMSNetwork
eNode B
eNode B
eNode BInternet PDN
IMS PDN S7
S6c
S5
S11
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LTE-Uu
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IMS Core (Control Layer)
Interrogating (I-CSCF)
• Provides a gateway to other domains (e.g. when a message or servicemust traverse multiple IMS domains)
EPCE-UTRAN IP Services
Internet
IMSNetwork
eNode B
eNode B
eNode BInternet PDN
IMS PDN S7
S6c
S5
S11
S6a Wx
LTE-Uu
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IMS Core (Control Layer)
HSS (Home Subscriber Server)
• Securely stores user profile information
• S-CSCF uses Diameter protocol to access HSS
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
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IMS Core (Control Layer)
SLF (Subscriber Location Function)
• Identifies which HSS contains the user’s profile if multiple HSS are in use
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-
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Rx
SGi
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IMS Core (Control Layer)
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
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-
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Rx
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IMS Core (Control Layer)
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
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-
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Rx
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IMS Core (Control Layer)
SGW (Signaling Gateway)
• Interfaces with the signaling plane of Circuit Switched (CS) networks
EPCE-UTRAN IP Services
Internet
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eNode B
eNode BInternet PDN
IMS PDN S7
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S5
S11
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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
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How SIP Stacks Up
SIP is not dependent on the underlying protocols
Physical
Data Link
IP
TCP/UDP
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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
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SIP Requests
SIP Requests have the format:
<request start line><request headers> (several lines)<blank line><message body>(carries the SDP message)
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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
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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
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SIP Responses
SIP Responses have the format:
<response status line><request headers> (several lines)<blank line>
<message body>
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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
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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
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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
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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
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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
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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
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SESSION INITIATION PROTOCOL(SIP) MESSAGING
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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
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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
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EPS Attach and P-CSCF Discovery
UE must first complete EPS Attach, establish EPS bearercontext and discover which P-CSCF(s) to use
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EPS Attach and P-CSCF Discovery
After RRC Connection is established, UE does an ATTACHREQUEST message and includes a PDN CONNECTIVITY REQUESTmessage
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EPS Attach and P-CSCF Discovery
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
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EPS Attach and P-CSCF Discovery
UE must first complete EPS Attach, establish EPS bearercontext and discover which P-CSCF(s) to use
EPS A h d P CSCF Di
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EPS Attach and P-CSCF Discovery
After Authentication, Security and UE Capability requests,network accepts Attach and activates EPS bearer context
EPS Att h d P CSCF Di
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EPS Attach and P-CSCF Discovery
After Authentication, Security and UE Capability requests,network accepts Attach and activates EPS bearer context
IMS PDN
One or more P-CSCF IPaddresses provided
LTE Evolved Packet System
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EPCE-UTRAN IP Services
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
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EPCE-UTRAN IP Services
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
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EPCE-UTRAN IP Services
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
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g gPackage Subscription
UE Attach ProcedureAttach Procedure Network
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IMS Initial Registration and Registration Event
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Package Subscription
UE Attach ProcedureAttach Procedure Network
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IMS Initial Registration and Registration Event
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Package Subscription
UE Attach ProcedureAttach Procedure Network
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IMS Initial Registration and Registration Eventk b
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Package Subscription
UE Attach ProcedureAttach Procedure Network
UE hascompletedinitial IMS
registration
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VoLTE Call Example
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EPCE-UTRAN IP Services
Internet
eNode B
eNode B
S5
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LTE-Uu
S1-U
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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
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EPCE-UTRAN IP Services
Internet
eNode B
eNode B
S5
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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
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EPCE-UTRAN IP Services
Internet
eNode B
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IMS Regi st r at i on v i a SIP Signal i ng
IMS
Rx
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IMS Registration
IMS authenticates, learns UE features
IMS Initial Registration and Registration EventPackage Subscription
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UE hascompletedinitial IMS
registration
Package Subscription
UE Attach ProcedureAttach Procedure Network
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IMS Initial Registration and Registration EventPackage Subscription
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UE hascompletedinitial IMS
registration
Package Subscription
UE Attach ProcedureAttach Procedure Network
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IMS Initial Registration and Registration EventPackage Subscription
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UE hascompletedinitial IMS
registration
Package Subscription
UE Attach ProcedureAttach Procedure Network
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IMS Initial Registration and Registration EventPackage Subscription
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UE hascompletedinitial IMS
registration
Package Subscription
UE Attach ProcedureAttach Procedure Network
UE hascompleted
subscriptionto the
registrationevent
package
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VoLTE Call ExampleSubscr i be t o Reg Event Package
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EPCE-UTRAN IP Services
Internet
eNode B
eNode B
S5
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S6a
LTE-Uu
S1-U
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SGi/Gm
SGi
Subsc be o eg e ac age
IMS
Rx
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ISC
Sh
Cx
S6b
SWx
S5
Subscribe to Reg Event Package
SMS
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Mobile-Originated SMS
UE IMS Registration ProcedureIMS Registration Procedure Network
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Mobile-Originated SMS
UE Attach ProcedureAttach Procedure Network
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Mobile-Terminated SMS
Mobile-Originated SMS
UE Attach ProcedureAttach Procedure Network
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Mobile-Terminated SMS
Mobile-Originated SMS
UE Attach ProcedureAttach Procedure Network
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THE KILLER APPS OF 2012
IMS Applications - Vision
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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
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Multiple IMS applications are actively being developed and/ordeployed on UEs now
• Registrations
• SMS• Voice over IP over IMS (aka VoLTE)
• Video Telephony
• Presence
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EVOLUTION OF VOICESERVICES WITH LTE
Evolution of Voice Services with LTE Networks
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2011 2012 2013
CDMALegacy
SVLTEVoLTE +
1X CS
LTE-only
Voice Devices
UMTSLegacy
SRVCCVoLTECSFB
SVLTE – Simultaneous Voice and LTE
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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IMS RegistrationIMS Registration
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More about theSIP INVITE SDP
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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>
More about theSIP INVITE SDP
(session attributes)
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(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
More about theSIP INVITE SDP
(rtpmap and fmtp
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(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
VoLTE Call Flow – UE-Initiated Call
UE1 UE2CSCF
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IMS RegistrationIMS Registration
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VoLTE Call Flow – UE-Initiated Call
UE1 UE2CSCF
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RTP Voice Traffic
IMS RegistrationIMS Registration
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EPCE-UTRAN IP Services
VoLTE Call ExampleUE usi ng Int ernet , No act i ve Voi ce Cal l
C
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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
EPCE-UTRAN IP Services
VoLTE Call ExampleIn i t i at e Voice Cal l
Cx
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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)
EPCE-UTRAN IP Services
VoLTE Call ExampleIn i t i at e Voice Cal l
Cx
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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
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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
EPCE-UTRAN IP Services
VoLTE Call ExampleIn i t i at e Voice Cal l
Cx
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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
EPCE-UTRAN IP Services
VoLTE Call ExampleIni t i at e Voice Cal l , Dedicat ed Bearer Est abl i shed f or Voice
Cx
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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
EPCE-UTRAN IP Services
VoLTE Call ExampleVoi ce Conversat i on
Cx
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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
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Existing call between UE1 & UE2Existing call between UE1 & UE2
EPCE-UTRAN IP Services
VoLTE Call ExampleTerminat e Cal l
Cx
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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
EPCE-UTRAN IP Services
VoLTE Call ExampleTerminat e Cal l
Cx
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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
EPCE-UTRAN IP Services
VoLTE Call ExampleNo Voice Call, Dedicated Bearer Deleted
IMS
Cx
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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
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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
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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)
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( )
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
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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
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R&D Testing of IMS
VoLTE Testing Methodologies
Interoperability – Protocol Analysis
• SIP, SDP
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• 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
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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
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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
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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
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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
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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)
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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
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LIVE DEMONSTRATION
CS8: For All Phases of Device Development
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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)
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Multi-RAT network emulation
• LTE, WCDMA, HSDPA, CDMA, EV-DO
Real-time responses from network-grade protocol engine
CS8 for Protocol Testing
The industry’s most complete and realistic Evolved Packet Core(EPC)
• The same EPC emulation used to test infrastructure products
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p
True IPv6 network emulation
• (not just IPv6 headers!)
• UE-to-Server Connectivity
CS8 for Protocol Testing
Interactive UI for intuitive LTE performance testing for• Data throughput
• Data retry
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• Data retry
• Inter-RAT handovers
Protocol testing• Simulate end-to-end tests for Protocol Rejects and Negative responses
CS8 for Adversarial Protocol (NAS/RRC)
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• Data Retry protocol tests
Demonstration Scenario
Done in Field Done in Office / Lab
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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
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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
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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