new challenges for ue developers with voice transport over lte · 2012-06-14 · •ims essential...

© 2012 Agilent Technologies

Wireless Communications

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New challenges for UE developers with voice transport over LTE



2 © 2012 Agilent Technologies



Agenda

LTE, Voice and SMS – Overview

IMS, SIP, Network Protocol Considerations

UE and Radio Access Considerations

SRVCC, CSFB, SVLTE and interworking

Voice Quality Testing and Agilent Solutions






Support for Voice with LTE

2G/3G – normal Circuit Switched calls have an allocated resource even

during times of inactivity - even when nothing is being said

• Inefficient use of available bandwidth

• Reduced flexibility for resource allocation

LTE – UE will generally only be provided resources when it is necessary –

even for voice

• Allows efficient use of network resources. If we are saying nothing we will

require no network resources

• Places stress on the network to ensure suitable access timing and quality

of service (QoS).

LTE transportation is fully IP – no circuit switched services






Support for Voice with LTE

Most agree that the long term solution for voice is to use VoIP and an IMS

based core network - However it will take time for networks to support this

For networks which do not support IMS several technologies are being

considered, namely:-

• CSFB (Circuit Switched Fall Back) - single radio approach

• SVLTE or Dual Standby approach (Simultaneous Voice and Data LTE) -

dual radio approach

• SRVCC (Single Radio Voice Call Continuity) – Voice on LTE with CS

backup

• CSFB, SVLTE and SRVCC all involve some level of I-RAT behavior

VoLGA (Voice over LTE Generic Access), does not appear to be getting a lot

of support.






IMS (IP Multimedia Subsystem)

• 3GPP defined IMS in 1999

• All-IP enabler for value added services

• After a slow start, growth accelerating

50-70% per annum.

• IMS-based VoLTE prevails over VoLGA

• IMS essential for Voice over LTE

• 2009 One Voice; AT&T, Orange, Telefonica, TeliaSonera,

Verizon, Vodafone, Alcatel-Lucent, Ericsson, Nokia Siemens, Networks,

Nokia, Samsung and Sony Ericsson

• 2010 VoLTE adopted by GSMA

IMS equipment revenue

progression






SIP and IMS

• SIP (Session Initiation Protocol) was initially designed to work in an open

homogeneous IP network

• SIP provides the signalling required to support call set-up procedures

• SIP also provides many other services (caller id, multi-party & emergency

calls…)

PSTN IP Network

GSM

3G IP Network

Telephone Network

SIP server






SIP and IMS

P headers

Planning

SIP

IPv6

Commercial Req

Architectural

req

Legacy Req

Link Quality Mgt

Firewall Needs

QoS support

Legacy services

999 services

Caller id

Lawful intercept

Accounting

Billing

Security

Protocols

SIGCOMP

Planning

ENUM

COPS

DIAMETER

IPsec

MD5-AKA

Common Open Policy Service Used to communicate a users QoS policy info to routers

ENUM Maps telephone numbers to IP addresses

SIGCOMP Used for compression purposes

P headers Feature extension for 3GPP

DIAMETER Protocol used to support AAA

IPsec Security protocol for IP links

MD5-AKA Security protocols used in 3G

IMS Extensions






IMS uses SIP-Session Initiation Protocol

REGISTER REGISTER

OK OK

INVITE

INVITE TRYING

TRYING

RING RING

OK OK

ACK ACK

BYE BYE

ACK ACK

RTP/RTCP

User A User B CSCF Proxy

m=audio 49120 RTP/AVP 98 97

a=rtpmap:98 AMR/8000

a=fmtp:98 mode-set=7

Optional AKAv2 authentication and IPsec

SIP (Session Initiation Protocol) e.g. INVITE, TRYING, RING, OK, BYE etc.

SDP (Session Description Protocol) e.g. m (media), a (attribute) etc.

RTP (Real-time Transport Protocol) e.g. AMR encoded speech

RTCP (RT Control Protocol) e.g. Send/receive quality metrics

CSCF = Call Session Control Function






RTP- Realtime Transport Protocol

RTP is used for the delivery of the user data,






RTCP

Realtime Transport Control Protocol

RTCP (RFC3550)

• Packet Loss Rate

• Jitter

• Timing Information

RTCP XR (RFC3611)

• Delay

• Signal Level

• Noise Level

• Call metrics

• Buffering






IP Sec

Tunnel Mode (VPN like)

• Entire original IP datagram encrypted

• Client to Server

Transport Mode

• Between two end points

AH added to protect against alteration of datagrams while in transit

Differences between the key generation between LTE and “Vanilla” network IP Sec

IP Header Data

IP Header AH Data

New IP Hdr AH IP Header Data

Transport Mode

Tunnel Mode

Normal IP traffic

More info in

RFC4301, 4302, 4303






SigComp - SIP Signalling Compression

State full Compressor

/De-compressor

SIP/SDP signalling

stack

RTP/RTCP

Media stack

• Compresses text based SIP and

SDP messages

• Up to 3:1 compression

• Standardized by the IETF RoHC

working group






SMS over SGs

What if my network does not support IMS, how do I get SMS?

SMS over SGs – Normal circuit switched “native” SMS is encapsulated message within NAS messaging

SGs is actually the interface between the MME and MSC, normally used for mobility management processes between 2G/3G and LTE

Requires combined attach with SMS only update IE.

Example from Agilent PXT, N6062A Message Editor






Agenda

14











VoIP QoS and Multiple PDN’s

Strict packet delay-based QoS

QoS will vary by allocation, by

application and will be heavily

dependent on system capacity.

UE’s can have multiple data streams,

Multiple PDN’s, Addresses, Port

numbers etc. – All with different

parameters:

•Default DRB or Dedicated DRB

•Guaranteed or non Guaranteed Bit Rate

•Packet delay budget e.g. 50 to 300ms

•Packet Error rate e.g. 10-2 to 10-6 Example from Agilent PXT, N6062A Message Editor






Traffic Flow Template

Traffic Flow Template (TFT)

Sort IP packets based on;

•IP protocol; e.g. UDP, TCP

•Port number

•IP address

•Priority

e.g. Browser

Non-GBR, low error

Dedicated

Internet IMS-SIP

Default

GBR, high error

IPv4/6

address 1

IPv6

address 2

Example configuration

e.g. IMS-SIP signalling

e.g. RTP voice stream

TFT

Applic

ations

IP p

ackets

LT

E R

adio

UE RF

IP2

SIP

RTP

IP1

http://www.google.co.uk/imgres?imgurl=http://www.accessyoutubeinchina.com/wp-content/uploads/youtube_logo2.jpg&imgrefurl=http://www.accessyoutubeinchina.com/youtube-blocked-in-china/&usg=__GgFbA9HqSXuy-gSJSYh43mRspWo=&h=310&w=413&sz=17&hl=en&start=2&zoom=1&tbnid=P5L3xns34LJS0M:&tbnh=94&tbnw=125&ei=N06YTp63IsnIswbj7uWKBA&prev=/search?q=you+tube&hl=en&sa=N&gbv=2&tbm=isch&itbs=1

http://www.google.co.uk/imgres?imgurl=http://www.headsure.com/wp-content/uploads/2010/06/Google-Chrome-Browser.jpg&imgrefurl=http://www.headsure.com/headline/bing-a-search-engine-born-from-failure/&usg=__omr1pP6FGYqMEMyVsIlGzGqYSIc=&h=321&w=350&sz=54&hl=en&start=5&zoom=1&tbnid=wAsNyrpwAwV1tM:&tbnh=110&tbnw=120&ei=Wk6YTqyhBczVsgb75tiGBA&prev=/search?q=google&hl=en&sa=N&gbv=2&tbm=isch&itbs=1

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GBR, TFT, QoS, DRB’s signalled to UE

GBR

TFT

Negotiated

QoS

Dedicated bearer, linked to

default bearer







LTE Scheduling Optimizations for Voice

SPS

• LTE Web/data optimized scheduling adds overhead and latency for speech

• SPS reduces signalling overhead by making sticky allocations during talk bursts

• Reduces LTE PDCCH loading

TTI bundling

• Up to 4dB cell edge coverage improvement

• Repeat UL data multiple times, reducing probability of errors

• More signaling efficient, fewer errors and lower latency than segmentation and

more robust MCS

PRB

Time

SPS (Semi-Persistent Scheduling)

PRB

Time

TTI Bundling

TTI = Transmit Time Interval






Message Editor Example

SPS and TTI Bundling







ROHC - Robust Header Compression

Typical VoIP Header for IPv4 = 40bytes

Typical VoIP Header for IPv6 = 60Bytes

With a typical voice rate of 12kbps, uncompressed IPv6 headers represent approximately 60% of the data sent / received

LTE network efficiency very poor without RoHC

Robust Header Compression is therefore required for LTE VoIP.







RoHCv2 - Robust Header Compression

Applic

ations

IP p

ackets

LT

E R

adio

UE RF

Payload Header

Payload

Compressor

LTE Radio Layers

Payload Header

Payload

De-

Compressor

LTE Radio Layers

Network

RoHC

Context

RoHC

Context

• Cuts IP overhead e.g. RTP streams for speech;

2:1 for IPv4, 3:1 for IPv6

• RoHCv2 simplification robustness handling of out-

of-sequence packets

http://www.google.co.uk/imgres?imgurl=http://www.accessyoutubeinchina.com/wp-content/uploads/youtube_logo2.jpg&imgrefurl=http://www.accessyoutubeinchina.com/youtube-blocked-in-china/&usg=__GgFbA9HqSXuy-gSJSYh43mRspWo=&h=310&w=413&sz=17&hl=en&start=2&zoom=1&tbnid=P5L3xns34LJS0M:&tbnh=94&tbnw=125&ei=N06YTp63IsnIswbj7uWKBA&prev=/search?q=you+tube&hl=en&sa=N&gbv=2&tbm=isch&itbs=1

http://www.google.co.uk/imgres?imgurl=http://www.headsure.com/wp-content/uploads/2010/06/Google-Chrome-Browser.jpg&imgrefurl=http://www.headsure.com/headline/bing-a-search-engine-born-from-failure/&usg=__omr1pP6FGYqMEMyVsIlGzGqYSIc=&h=321&w=350&sz=54&hl=en&start=5&zoom=1&tbnid=wAsNyrpwAwV1tM:&tbnh=110&tbnw=120&ei=Wk6YTqyhBczVsgb75tiGBA&prev=/search?q=google&hl=en&sa=N&gbv=2&tbm=isch&itbs=1

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Agenda

22











GSM/W-CDMA/

TDSCDMA

1xRTT/eVDO/

eHRPD

Phone x Network Configuration

Only one network actively using IMS with LTE today.

Challenges with interoperability between legacy non-3GPP and LTE

LTE designed from IP viewpoint, legacy systems optimised for Voice

Strict latency targets to ensure acceptable voice quality.

Different use models and progression towards VoLTE depending on

existing network RAT.

LTE

http://www.google.co.uk/imgres?imgurl=http://www.femtohub.com/ext_media/pictures/fullsize-rT4muQFN3oJnVrg.gif&imgrefurl=http://www.femtohub.com/topic/profile/3gpp/?page=30&usg=__1NFRoXmRn_EQ7D8yIBiDLwHJ5tc=&h=146&w=250&sz=11&hl=en&start=8&zoom=1&tbnid=K5t5719p19XbyM:&tbnh=65&tbnw=111&ei=AIekTq3vNsmKswbXl5D7Ag&prev=/search?q=3GPP&hl=en&gbv=2&tbm=isch&itbs=1

http://www.google.co.uk/imgres?imgurl=http://digitalmedia.oreilly.com/images/oreilly/digitalmedia/2005/08/mpeg4-3gpp2-logo.gif&imgrefurl=http://digitalmedia.oreilly.com/2005/08/24/mpeg4.html?page=2&usg=__ke0YYnU4JHBXZ-_R64TRL5Oz_38=&h=165&w=165&sz=5&hl=en&start=3&zoom=1&tbnid=RcacGBiShTxFcM:&tbnh=99&tbnw=99&ei=P4ekTrmmOsXrsgbS88ibAw&prev=/search?q=3GPP2&hl=en&sa=G&gbv=2&tbm=isch&itbs=1

http://www.google.co.uk/imgres?imgurl=http://www.4gamericas.org/UserFiles/image/Board_of_Governors_Logos/LTE-Logo.jpg&imgrefurl=http://www.4gamericas.org/index.cfm?fuseaction=page&sectionid=249&usg=__g9OzpSg8L-C0i9paCUWSl7FbpLM=&h=1200&w=1315&sz=62&hl=en&start=1&zoom=1&tbnid=9Hz9uaH9RwbuPM:&tbnh=137&tbnw=150&ei=g4ekTrW5DM_dsgbUsJyTAw&prev=/search?q=LTE&hl=en&gbv=2&tbm=isch&itbs=1






GSM/W-CDMA/

TDSCDMA

1xRTT/eVDO/

eHRPD


SVLTE Simultaneous Voice & LTE aka Dual Standby

•Two phones in one case

•1xRTT (or GSM/W-CDMA) chipset for all voice calls (CS only)

•LTE/eVDO/eHRPD (and/or W-CDMA) separate chipset for data

LTE/eVDO/HRPD radio

1xRTT CS radio CS Voice Client

e.g.

GUI

LTE









GSM/W-CDMA/

TDSCDMA

1xRTT/eVDO/

eHRPD


CSFB Circuit Switched Fall Back

•Handover from LTE to legacy 2G/3G for ALL voice calls

•Use Circuit switched voice (and if available parallel slower legacy data)

LTE/W-CDMA/GSM radio

CS Voice Client

e.g.

GUI

LTE









GSM/W-CDMA/

TDSCDMA

1xRTT/eVDO/

eHRPD


SRVCC Single Radio Voice Call Continuity

•IMS voice calling in LTE coverage areas

•Quickly handover from LTE to legacy 2G/3G at LTE edge

CS Voice Client GUI

e.g.

IMS Voice Client LTE/W-CDMA/GSM radio

LTE









GSM/W-CDMA/

TDSCDMA

1xRTT/eVDO/

eHRPD


LTE / IMS Only

•IMS voice calling in LTE coverage areas

LTE radio

GUI

e.g.

IMS Voice Client

LTE









GSM/W-CDMA/

TDSCDMA

1xRTT/eVDO/

eHRPD

LTE


SVLTE Simultaneous Voice & LTE

Aka Dual Standby

CSFB Circuit Switched

Fall Back

SRVCC Single Radio Voice

Call Continuity

LTE/ IMS

islands

LTE / IMS only

Most Operators will skip some steps

World phones will need to roam with many network configurations

LTE/eVDO/HRPD/GSM/W-CDMA/

TDSCDMA radio

1xRTT CS radio CS Voice Client GUI

e.g.

IMS Voice Client









Agenda











Various Test Forms

Voice quality – PESQ, POLQA etc.

• Codec testing, inter-codec rate testing

• Handling for packet delays, lost/un-ordered packets

SARS test

Signalling testing

• Origination, registration, notifications etc.

• Supplementary services – multi-party calls, call on

hold etc. – voice and data interactivity

• Signalling Conformance Testing – 3GPP TS 34.229

Radio testing for VoIP functions

• Semi-persistent scheduling, TTI bundling, dynamic

small allocation testing

Handovers, SRVCC, CSFB

Battery drain

SMS and Video call testing

Operator Specific Test Plans

Field Testing






Testing to Improve User Experience

Start with infrastructure IOT, quickly move to simulated bench-top networks then automated conformance testing of new UEs

Infrastructure IOT Bench-top network Automated Conformance

Test

//upload.wikimedia.org/wikipedia/commons/6/60/Ims_overview.png






IFT for 2G/3G Battery Drain Analysis

Client:

•Interactive Functional Test (IFT)

•Wireless Protocol Advisor

•License Keys

•Modem drivers

Server:

•FTP server

•UDP Server

•Apache HTTP server

•MMS/SMS server

PSU:

•Current monitoring

8960:

•2G/3G BS emulation

http://www.itechnews.net/wp-content/uploads/2008/10/att-blackberry-bold-smartphone.jpg



IFT for 2G/3G Battery Drain Analysis

Server:

•FTP server

•UDP Server


•MMS/SMS server

PSU:


Client:



•License Keys

•Modem drivers

IFT:

•Activities; SMS, FTP, HTTP,

USP, calls

•Parallel threads

•UE automation

•Drag & Drop programming

•VB scripting

33

http://www.itechnews.net/wp-content/uploads/2008/10/att-blackberry-bold-smartphone.jpg






IFT for 2G/3G/LTE Battery Drain Analysis

Client:



•License Keys

•Modem drivers

Server:

•FTP server

•UDP Server


•MMS/SMS server

•IMS-SIP server/client

PSU:


8960:

•2G/3G BS emulation

PXT:

•LTE BS emulation

IMS-SIP server and client:

•SMS-IMS

•VoIP, Video

•Logging

PXT:

•100Mbps

•Multiple DRB

•IPv6






IMS/SIP Server Client for VoLTE Test

UE

PXT LTE cell

E6621A

Message Logging

Hub

Hello!

Hello!

Multiple Dedicated DRBs

RoHC

SPS

TTI bundling

SIGCOMP

P headers …

CODEC support

…

Key VoLTE features






Audio Test Scenario 1 Human jury testing and/or PESQ with IP impairments

RF RF

Ethernet

Delay/Jitter/Loss insertion

Agilent IMS-SIP server

Agilent PXT Agilent PXT

VoLTE UE VoLTE UE

Audio in/out headphone jack or HATS Audio in/out headphone jack or HATS

Audio Analyzer






Audio Test Scenario 2 Parametric audio quality and noise suppression

RF

Optional Delay/Jitter/Loss insertion

Agilent IMS-SIP server

+ Client

Agilent PXT

VoLTE UE

Ethernet

Audio Analyzer

Analogue audio to HATS Mic/Speaker or headphone jack

Reference Audio I/O

USB

Analogue audio I/O

Optional audio noise






Functional Test Scenario x IMS/CS voice calling & Inter-RAT scenarios

RF

Agilent 8960

1xRTT cell

Agilent 8960

eHRPD cell

Agilent PXT

LTE cell

Ethernet

Test

automation Agilent IMS server and

several remote clients






Verizon Inter-RAT Test Automation www.agilent.com/find/N5973A

Leading Inter-RAT test coverage

• Efficient, repeatable testing: Fully automated

execution including UE control and report

generation, runs unattended

• Includes IMS-SIP server and IPv6

• Extend to SVD/SVLTE Inter-RAT as UE available

• Builds on Agilent Interactive Functional Test

Software, expandable to other test plans

Supports Agilent’s

established 8960

and PXT test sets

http://www.agilent.com/find/N5973A






Useful References

ITU-T P.862. Perceptual evaluation of speech quality (PESQ)

ITU-T P.863. Perceptual Objecting Listing Quality Assessment (POLQA)

PXT Website. www.agilent.com/find/PXT

Agilent IMS/SIP www.agilent.com/find/E6966A

Interactive Functional Test (IFT). www.agilent.com/find/IFT

GSMA IR.92 IMS Profile for Voice and SMS

3GPP TS 34.229 IP Multimedia call control protocol based on SIP and SDP, UE conformance specification

3GPP TS 33.178 Security Aspects of early IP Multimedia Subsystems (IMS)

3GPP TS 26.114 IP Multimedia Subsystems (IMS) Multimedia telephone: Media handling and interaction

3GPP TS 26.132 Speech and video telephony terminal acoustic test specification

3GPP TS 22.173 IP Multimedia Core Network Subsystem Multimedia Telephony Service and supplementary services

3GPP TS 23.228 IP Multimedia Subsystem (IMS) Stage 2

http://www.agilent.com/find/PXT

http://www.agilent.com/find/E6966A

http://www.agilent.com/find/IFT






Summary

IPv6, IP Sec, SigComp, Multiple DRB’s, QoS, Multiple IP addresses,

IMS, SIP, TTI Bundling, Semi Persistent Scheduling, VoIP, POLQA,

PESQ, RTP, RTCP, SRVCC, CSFB, SVLTE, SDP, SMS over SGs

Enough reasons to start testing VoLTE now ?






Backup slides






LTE 3GPP Stack Overview – PDCP

Robust Header Compression

(RoHC)

• For more info see IETF

RFC 4995.

• Reduced overhead, more

efficient

Once RoHC has been applied

the whole packet (data AND

header) are ciphered as per

35.201 (data only)

Headers and Message

Authentication codes are

added

IP

Header Data

Data

PDCP

Header C%^b£$^8Df%^!z(£”*v& MAC-I

Ciphered

RoHC applied

Header and

data ciphered






POLQA ITU-T P.863 Perceptual Objective Listening Quality Assessment

http://www.polqa.de/index.html © Optimcom GmBH

http://www.polqa.de/index.html






Rich Communication Suite (RCS)

RCS is an industry effort focused on the use of IMS (IP Multimedia Subsystem) for providing mobile

phone communication services. "Rich Communication" in itself is meaningless jargon, which refers to the

use of more than just voice for communication, but has long been touted as a benefit of IMS. It is to be

noted that much of the capability of RCS is already available from Internet service providers.

According to the press release,[1] from the end-user point of view RCS would enable communication

such as instant messaging, video sharing and buddy lists. These capabilities would be available on any

type of devices using an open communication between devices and networks. Main features of RCS are:

Enhanced Phonebook, with service capabilities and presence enhanced contacts information

Enhanced Messaging, which enables a large variety of messaging options including chat and messaging

history

Enriched Call, which enables multimedia content sharing during a voice call. For many years Nokia and

Ericsson have been pushing a "see what I see" capability, but this has failed to be taken up by operators,

or the way it was deployed failed to result in great take-up by consumers. Bundling this feature with the

two other features may help to increase uptake.

Wider and large scale IMS deployment, Interoperability between different terminal vendor RCS clients

and RCS service interworking between operators are the key aims of RCS Initiative. However, RCS is

considered by some to be not fit for purpose [2] and has not been rolled out commercially by any major

operator as of September 2010. [1] http://www.nokia.com/A4136001?newsid=1189463

http://www.nokia.com/A4136001?newsid=1189463



LTE VoIP Test Building Blocks

Agilent U8903A Audio Analyzer

IMS-SIP TTCN-3 Signaling Test

Agilent

Agilent PXT LTE Test Set

Agilent IMS-SIP Server

Agilent IMS-SIP Client

Agilent PESQ Measurement IP

Partners of Agilent

Other Measurement IP e.g. POLQA Standards compliant HATS testing

46



• Procedure

• PXT sends either RRC release or Mobility from E-UTRA command

• UE joins 3G cell

• The UE is redirected to the 8960 and automatically completes the call setup. The 8960 receives a

page response from the UE and continues to setup the call.

CSFB

47



CSFB (c2k requires s101 control plane tunnel)

• CSFB requires 2 baseband ICs (LTE + alternative RAT) with some opportunity to share RF resources

• For c2k there is significant additional protocol complexity vs. SV-LTE

• For c2k CSFB a control plane tunnel is required in order to pre-register with the c2k cell (via LTE signaling) – this is known as an optimized handover

• 2G/3G CSFB does not need this as all RATs share the same core network

• CSFB is being considered for voice on many 2G/3G/LTE networks

• VZW will ultimately support voice using IMS and will then use optimized handovers between LTE and eHRPD

• Agilent are developing optimized handovers for the PXT/8960.

UE Serving eNB

Broadcast neighbour cell info

Attach with Serving eNB

Configure measurement reports

Send measurement reports

Tunnel paging info from CDMA BTS to LTE enB RRC release with re-direction to CDMA BTS

S101 control plane tunnel

CDMA BTS

register UE with 1x cdma2000 base

station

S101 control plane tunnel

Establish voice call between UE and CDMA cell

Page UE

48

new challenges for ue developers with voice transport over lte · 2012-06-14 · •ims essential...

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