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VoLTE-NSN

Voice over LTE

Telephony on the National Public Safety Broadband Network

Brian Kassa

Head of Technology – Public Safety Broadband June 5th, 2013

Public Safety Broadband

Agenda

??VoLTE Overview ??What is VoLTE ??

VoLTE for FirstNet

Public Safety Broadband

Setting the scene for voice in the LTE era

The industry known options for voice are:

??Circuit switched fallback (CSFB) ??IMS based VoLTE (VoLTE)

??Simultaneous voice and data (SV-LTE)

A voice solution is needed for an LTE smartphone to connect to LTE network, otherwise it is connected to 2G/3G only – for voice and data.

LTE

2G/3G

3G PP

Public Safety Broadband

Foreseen Voice over LTE Technology Evolution

2012

2013

Dual radio terminals for CDMA /LTE operators SV-LTE

VoLTE with QoS

VoLTE with SRVCC

CS Fallback to 2G/3G

Voice over CDMA and data over LTE

Voice over 2G/3G and data over 2G/3G or LTE

Seamless voice continuity

Secured voice quality

2014 SMS over LTE connection

Over the air configuration, prepaid information

VoLTE roaming

2015

Smartphone launch on LTE networks means that a voice solution must be

implemented

SVLTE

CSFB VoLTE SRVCC

LTE coverage Network impact

Terminal

impact

Public Safety Broadband

Agenda

??VoLTE Overview ??What is VoLTE ??

VoLTE for FirstNet

Public Safety Broadband

VoLTE system architecture

The Obligatory Spaghetti Diagram

MME

S-GW P-GW

eNB

HSS

PCRF

P-CSCF

I/S-CSCF BGCF MGW

TAS

GERAN/UTRAN

MGW

MGCF

Call control signalling User plane traffic Other control signalling

S6a

Ma, ISC Sh

S11

S1-MME S1-U

SGs Sv

Cx Mi

MSS

LTE-Uu

EPS

IMS

What Is Needed for VoLTE

1. Circuit Switched Fallback (CSFB)

2. Single Radio Voice Call Continuity (SRVCC)

3. Rich Communications (RCS)

4. IMS Centralized Services (ICS) 8. Roaming 7. Lawful Intercept (LI) 6. Emergency Call (911)

5. Domain Selection (T-ADS) Assumed : LTE Network with QoS, Location and Charging

9. Terminals

Public Safety Broadband

Main drivers

LTE Voice and Messaging Evolution

VoLTE

??QoS for voice

??Based on all-IP network architecture

??Provides similar tools to fight OTT ??Improved voice spectral efficiency of LTE, short call setup time, short delays RCS

? Richer service offering to attract users

? Alternative service offering to OTT ? Works with CSFB and VoLTE

1 RCS can be introduced at any time, works with both CSFB and VoLTE

CS Fallback

??Immediate voice solution for LTE ??Roaming before VoLTE roaming ??Emergency calls before IMS based VoLTE in place

??SMS over SGs before SMS o IP

(Simplified for clarity, visited network and roaming not shown)

BSC / R NC

BSS/NB PGW

eNB

M SS

MME

MGW

SMSC

HLR

SGW

CSFB SMS

1. CSFB + SMS over SGs

2. VoLTE RCS

3. SRVCC Voice

Voice TAS SR--‐VCC

Sv SGs Voice core

LTE packet core

LTE radio network

2G/3G radio network

IMS

PCRF

HSS

4. RCS 1

IP n etwork

MNO PSTN

Public Safety Broadband SRVCC in 3GPP

??SRVCC has been standardized in

3GPP Release 8 TS 23.216 to

provide seamless continuity for UE

handovers from E-UTRAN to

UTRAN/GERAN.

3GPP Release 10 targets to

enhance SRVCC performance in

roaming cases.

3GPP Release 10 introduces two

new functional entities for SRVCC:

ATCF and ATGW.

ATCF Access Transfer Control Function

ATGW Access Transfer Gateway

Public Safety Broadband

- a simple interoperable extension to voice and

SMS . . .

Messages (SMS/MMS)

Voice

Initial ?joyn‘ Service Set

New services to monetize market trends RCS-e

Public Safety Broadband

. . . and a basis to continuously deliver innovation

RCS 5 is completely backward compatible with RCS-e V1.2

specifications and also includes features from RCS 4 and exciting new features such as IP video call, IP voice call and Geo-location exchange.

RCS 5

= new features (not part of RCS-e 1.2)

Public Safety Broadband

??3GPP VoLTE/IMS Roaming Alternatives

–?the alternatives differ in:

–?Architecture: different network elements (P-CSCF, PCRF, PGW) are located in home- and visited networks. –?Regulatory Service Support: ability to provide local support for IMS Emergency Calls and Lawful Interception. –?Bearer Support: ability to support an optimized routing for the bearer.

–?today, operators typically have the GGSN/PDN-GW in the Home Network (= Alternative 3) –?GSMA IR.92 “One Voice” recommends Alternative 1:

–?due to the flexibility to serve regulatory needs (LI, Emergency Calls) and to support optimized routing.

–?the roaming architecture however always also depends on the abilities of the roaming partners (who might not have an IMS at

all).

IMS Roaming / LTE Roaming Support and Evolution

Visited Network (of the A-Party) Home Network (of the A-Party)

Terminating Network (Home of the B-Party)

V-PCRF

H-PCRF

PDN -PGW

I-/S-CSCF

V-PCRF

H-PCRF

PCRF

VoLTE/ IMS Alternative 1

VoLTE/IMS Alternative 2

VoLTE/IMS Alternative 3

PDN-PGW

P-/E-CSCF

I-/S-CSCF

P-/E-CSCF

SIP Signaling SIP Signaling

SIP Signaling

VoIP Bearer

Serving-GW

Visited Network (of the A-Party)

Home Network (of the A-Party)

Visited Network (of the A-Party)

Home Network (of the A-Party)

Terminating Network (Home of the B-Party) Terminating Network (Home of the B-Party)

P-/E-CSCF

I-/S-CSCF

UE (A-Party)

Ic/Mw

Public Safety Broadband

1. Routing of media for Voice & video over IMS when call originator is Roaming should be at least as optimal as

that of current Circuit Switched (CS) domain.

2. The charging model for roaming used in CS domain shall be maintained in VoIMS.

3. Allow the HPMN to decide, based on service and commercial considerations & regulatory obligations, to enforce the routing of the traffic to itself (home routing).

GSMA IR.65

Operational Requirements for IMS Voice and Conversational Services

Public Safety Broadband

VoLTE (IR.92) in terminals

VoLTE (IR.92) Terminal industry trend is that VoIP (VoLTE IR.92) client will be integrated in a chipset

– not in a terminal as an separate

application 2G/3G CS voice

CSFB IMS VoIP LTE

CSFB and CS

2G/3G CS voice CSFB VoLTE client (GSMA IR.92) run on the modem processor while the application processor can enter sleep mode. The same approach is used for CS voice. Today VoIP (application) runs on top of OS in the application processor which is power hungry.

VoLTE (GSMA IR.92) calls are invisible to end user as those will be done same way as CS call – press the green button.

Voice clients (CS, CSFB, VoLTE, SRVCC)

integrated in chipset.

Public Safety Broadband

Agenda

??VoLTE Overview ??What is VoLTE ??

VoLTE for FirstNet

Public Safety Broadband LTE Voice implementation depends on operator conditions

Coverage evolution

VoLTE implementation Market situation

Capacity

demand

LTE

spectrum

Carrier

Relations

Existing

network

Public Safety Broadband

What Is Needed for VoLTE for FirstNet

1. Circuit Switched Fallback (CSFB)

2. Single Radio Voice Call Continuity (SRVCC)

3. Rich Communications (RCS)

4. IMS Centralized Services (ICS) 8. Roaming 7. Lawful Intercept (LI) 6. Emergency Call (911)

5. Domain Selction (T-ADS) 2G/3G Network Partner

2G/3G Network Partner

Assumed: LTE Network with QoS, Location and Charging

9. Terminals

Public Safety Broadband

IMS Roaming / LTE Roaming Support and Evolution

??Key Outbound Roaming Scenarios for a Firstnet VoLTE Subscriber

(with an 1xCS, LTE, 2G/3G UE) roaming in a visited network:

1.visited network that supports: 1xCS

2.visited network that supports: 1xCS, LTE Data

3.visited network that supports: 1xCS, VoLTE/IMS

4.visited network that supports: 2G/3G CS/PS

5.visited network that supports: 2G/3G CS/PS, LTE Data

6.visited network that supports: 2G/3G CS/PS, VoLTE/IMS

SCC-AS

MME SGSN

1xMSC

MSC

MME

1xMSC

IS41-MAP MAP

S6a P-CSCF

CSCF

1xHLR

HLR

HSS

Terminating Call

F i r s t N e t (H o m e ) N e t w o r k

V i s i t e d

N e t w o r k

IMS

PDN-GW

PDN-GW UE

(outbound 1xCS roamer)

(outbound 2G/3G roamer)

(outbound VoLTE roamer)

TAS

(FirstNet VoLTE subscriber)

Public Safety Broadband FirstNet LTE with CSFB to partner’s 2/3G

Partner’s 2/3G

network

Firstnet LTE

LTE

GSM/WCDMA

To PSTN

BSC RNC

2/3G

MSC/VLR

Iu-cs

HSS/ HLR

MAP

MME

S6a

SGs

2/3G

S3 and Gs are used for ISR.

S3 is also needed if PS-HO

for CSFB is used.

Legacy SGSN requires MME

to support Gn/Gp interface.

PLMN ID in LTE (PS) and

2/3G (CS) can be different.

Public Safety Broadband

MOC call flow from LTE to GERAN/UTRAN with redirection

UE/MS

eNB

BSS/RNS

MME

MSC

RRC Connection Request

RRC Connection Setup Complete with Extended Service Request (MO CSFB)

S1-AP message with CSFB Indicator

RRC Connection Setup

Optional Measurement Report Solicitation Location Area Update or Combined RA/LA Update (if LAI from radio is different than the one stored by the UE CS MO Call Establishment

RRC Connection and Extended Service messages

UE makes IRAT

measurements from GERAN/UTRAN cells

Redirection procedure

CS Call Setup

RRC Connection Release to GERAN or UTRAN

Location Update procedure