Jun5 kassa-adhoc net-arch-vo_lte

1 © Nokia Siemens Networks

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

UE

3GPP

3GPP


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



Agenda





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

Gx

Rx

Ma, ISC Sh

Mb S11 S1-MME

S1-U

SGs Sv

Mw

Cx Mi

Mn

D

MSS

LTE-Uu

EPS IMS

CS


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



Dept. / Author / Date

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 / RNC BSS/NB

PGW eNB

MSS

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. RCS¹

IP network

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

Source: operator & GSMA slides presented at the Informa ‘Rich Communication 2011’ conference, Munich, 25+26 Oct 2011

RCS-e


Public Safety Broadband . . . and a basis to continuously deliver innovation

Source: GSMA RCS 5.0 - Services and Client Specification

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)



•  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

PDN-PGW

P-/E-CSCF I-/S-CSCF

P-/E-CSCF SIP Signaling SIP Signaling

SIP Signaling

VoIP Bearer

VoIP Bearer

VoIP Bearer

Serving-GW







P-/E-CSCF I-/S-CSCF

UE (A-Party)

UE (A-Party)

UE (A-Party)

S8

Gm Gm

S9 S9

Ic/Mw



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.



Agenda





Public Safety Broadband LTE Voice implementation depends on operator conditions

Coverage evolution VoLTE implementation Market situation

Capacity demand

LTE spectrum

Carrier Relations

Existing network



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



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

2G/3G Network 1xCS Network LTE/EPC Network

Mw

(Visited) IMS Network

Firs

tNet

(H

ome)

N

etw

ork

Visi

ted

Net

wor

k

IMS

UE PDN-GW

PDN-GW

UE (outbound

1xCS roamer)

UE (outbound

2G/3G roamer)

UE (outbound

VoLTE roamer)

TAS

UE (FirstNet VoLTE subscriber)



FirstNet LTE with CSFB to partner’s 2/3G Partner’s 2/3G network

Firstnet LTE

Roa

min

g in

terfa

ces

LTE GSM/WCDMA

To PSTN

BSC RNC

2/3G MSC/VLR

A

Iu-cs

HSS/ HLR MAP

MME

S6a

SGs

2/3G SGSN

S3

Gs

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.

Gb/Iu-ps


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


Public Safety Broadband MT 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 and Emergency Indicators

RRC Connection Setup

Optional Measurement Report Solicitation

RRC Connection and Extended Service messages

UE makes IRAT measurements from GERAN cells

Redirection procedure RRC Connection Release to GERAN or UTRAN

CS Paging CS Paging

CS Paging

Location Area Update or Combined RA/LA Update

CS MT Call Establishment

Location Update procedure CS Call Setup

Paging Response A/Iu-cs message with paging response Paging Response



FirstNet LTE with eSRVCC to partner’s 2/3G Partner’s 2/3G network

Firstnet LTE

Roa

min

g in

terfa

ces

LTE GSM/WCDMA

To PSTN

BSC RNC

2/3G MSC/VLR

A

Iu-cs

HSS/ HLR MAP

MME

S6a

Sv

2/3G SGSN

2/3G SGSN

S3

S3 is used for eSRVCC with PS HO procedure (optional). Legacy SGSN requires MME to support Gn/Gp interface.

Gb/Iu-ps

Other VoLte functional elements: PCC/S/P-GW/P-CSCF/ATCF…

S1-U

S5



UE E-UTRAN MME MSC Server Target UTRAN/GERAN

MeasurementReports

SRVCC Handover to UTRAN/GERAN required (CS or CS+PS)

3GPP IMS

Initiates SRVCC for voice component

CS handover preparationIMS Service Continuity ProcedureHandles PS-PS HO for

non-voice if needed

P S-CS HO response to MME(CS resources)

To eUTRANCoordinates SRVCC and PS HO response Handover CMD

Handoverexecution

SRVCC indicationSRVCC possible indication

VoLTE session ongoing

High level flow for E-UTRAN SRVCC

Request to partner’s 2/3G network via Sv interface



E/I/S-CSCF BGCF

P-CSCF. BCF, ATCF

A-BGF ATGW MRFP

TAS

S/P-GW

CSFB/SRVCC/MGCF/GMSC

PCRF

eNB

ISC/SIP

Gx

Rx

Iq H.248

Gm/ SIP

CS/IMS-MGW 2G/3G CS/IMS-MGW

Example FirstNet VoLTE Solution Architecture

CS MSS

Mw/SIP

SIP HLR

HSS

SDM MME

Sv,SGs

Mc

Nc (ISUP/BICC/SIP-I)

E (MAP)

SMSC C (MAP)

E (MAP) FirstNet 2G/3G Partner

SGSN

E (MAP)



Thank you!

Jun5 kassa-adhoc net-arch-vo_lte

Engineering

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