Voice over LTE Telephony on the National Public Safety Broadband Network Brian Kassa Head of Technology June 5 th, 2013 1 Nokia Siemens Networks
Agenda VoLTE Overview What is VoLTE VoLTE for FirstNet 2 Nokia Siemens Networks
Setting the scene for voice in the LTE era 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. The industry known options for voice are: LTE Circuit switched fallback (CSFB) 3GPP UE IMS based VoLTE (VoLTE) 3GPP 2G/3G Simultaneous voice and data (SV-LTE) 3 Nokia Siemens Networks
Foreseen Voice over LTE Technology Evolution SMS over LTE connection Over the air configuration, prepaid information Dual radio terminals for CDMA /LTE operators SV-LTE Smartphone launch on LTE networks means that a voice solution must be implemented LTE coverage Network impact Voice over CDMA and data over LTE CS Fallback to 2G/3G Voice over 2G/3G and data over 2G/3G or LTE VoLTE with QoS Terminal impact Secured voice quality SVLTE CSFB VoLTE SRVCC VoLTE with SRVCC Seamless voice continuity VoLTE roaming 2012 4 Nokia Siemens Networks 2013 2014 2015
Agenda VoLTE Overview What is VoLTE VoLTE for FirstNet 5 Nokia Siemens Networks
VoLTE system architecture The Obligatory Spaghetti Diagram MSS GERAN/UTRAN MGW D CS TAS Sh Call control signalling User plane traffic SGs Sv HSS Cx I/S-CSCF BGCF Ma, ISC Mi MGCF Other control signalling LTE-Uu S1-MME MME S6a S11 PCRF Gx Rx Mw P-CSCF Mn Mb enb S1-U EPS S-GW P-GW IMS MGW 6 Nokia Siemens Networks
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) 5. Domain Selection (T-ADS) 6. Emergency Call (911) 7. Lawful Intercept (LI) 8. Roaming 9. Terminals Assumed: LTE Network with QoS, Location and Charging 7 Nokia Siemens Networks
LTE Voice and Messaging Evolution (Simplified for clarity, visited network and roaming not shown) 1. CSFB + SMS over SGs 2. VoLTE 3. SRVCC 4. RCS¹ Voice CSFB SR- VCC SMS Voice 2G/3G radio network BSS/NB BSC / RNC enb LTE radio network ¹ RCS can be introduced at any time, works with both CSFB and VoLTE Voice core HLR HSS SMSC TAS MSS IMS RCS Sv SGs MGW MME PCRF SGW PGW LTE packet core MNO PSTN IP network Main drivers 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 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 8 Nokia Siemens Networks Dept. / Author / Date
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. 9 Nokia Siemens Networks ATCF Access Transfer Control Function ATGW Access Transfer Gateway
- a simple interoperable extension to voice and SMS... New services to monetize market trends Initial joyn Service Set Messages (SMS/MMS) Voice RCS-e 10 Nokia Siemens Networks Source: operator & GSMA slides presented at the Informa Rich Communication 2011 conference, Munich, 25+26 Oct 2011
... and a basis to continuously deliver innovation RCS 5 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. = new features (not part of RCS-e 1.2) 11 Nokia Siemens Networks Source: GSMA RCS 5.0 - Services and Client Specification
IMS Roaming / LTE Roaming Support and Evolution 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). VoLTE/ IMS Alternative 1 VoLTE/IMS Alternative 2 VoLTE/IMS Alternative 3 Visited Network (of the A-Party) Home Network (of the A-Party) Visited Network (of the A-Party) Home Network (of the A-Party) Visited Network (of the A-Party) Home Network (of the A-Party) UE (A-Party) P-/E-CSCF SIP Signaling Ic/Mw I-/S-CSCF UE (A-Party) SIP Signaling Gm P-/E-CSCF I-/S-CSCF UE (A-Party) SIP Signaling Gm P-/E-CSCF I-/S-CSCF PCRF VoIP Bearer V-PCRF S9 H-PCRF VoIP Bearer V-PCRF S9 H-PCRF VoIP Bearer Serving-GW S8 PDN-PGW PDN -PGW Terminating Network (Home of the B-Party) PDN-PGW Terminating Network (Home of the B-Party) Terminating Network (Home of the B-Party) 12 Nokia Siemens Networks
GSMA IR.65 Operational Requirements for IMS Voice and Conversational Services 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). 13 Nokia Siemens Networks
VoLTE (IR.92) in terminals Terminal industry trend is that VoIP (VoLTE IR.92) client will be integrated in a chipset not in a terminal as an separate application 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. CSFB and CS CSFB 2G/3G CS voice VoLTE (IR.92) CSFB 2G/3G CS voice IMS VoIP LTE 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. 14 Nokia Siemens Networks
Agenda VoLTE Overview What is VoLTE VoLTE for FirstNet 15 Nokia Siemens Networks
LTE Voice implementation depends on operator conditions Market situation Capacity demand LTE spectrum Existing network Carrier Relations 16 Nokia Siemens Networks Coverage evolution VoLTE implementation
What Is Needed for VoLTE for FirstNet 1. Circuit Switched Fallback (CSFB) 2. Single Radio Voice Call Continuity (SRVCC) 2G/3G Network Partner 3. Rich Communications (RCS) 4. IMS Centralized Services (ICS) 2G/3G Network Partner 5. Domain Selction (T-ADS) 6. Emergency Call (911) 7. Lawful Intercept (LI) 8. Roaming 2G/3G Network Partner 9. Terminals Assumed: LTE Network with QoS, Location and Charging 17 Nokia Siemens Networks
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 IMS SCC-AS TAS CSCF Terminating Call FirstNet (Home) Network 1xMSC 1xHLR HLR HSS MME PDN-GW UE (FirstNet VoLTE subscriber) IS41-MAP MAP S6a Mw 18 Nokia Siemens Networks Visited Network UE (outbound 1xCS roamer) UE 1xMSC 1xCS Network MSC MME SGSN PDN-GW UE UE (outbound (outbound 2G/3G VoLTE roamer) roamer) 2G/3G Network LTE/EPC Network P-CSCF (Visited) IMS Network
FirstNet LTE with CSFB to partner s 2/3G LTE Firstnet LTE Partner s 2/3G network GSM/WCDMA 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. 19 Nokia Siemens Networks S6a HSS/ HLR MME S3 MAP SGs Roaming interfaces 2/3G SGSN A BSC 2/3G MSC/VLR Gs Iu-cs Gb/Iu-ps RNC To PSTN
MOC call flow from LTE to GERAN/UTRAN with redirection UE/MS enb BSS/RNS MME MSC RRC Connection Request RRC Connection and Extended Service messages RRC Connection Setup RRC Connection Setup Complete with Extended Service Request (MO CSFB) S1-AP message with CSFB Indicator UE makes IRAT measurements from GERAN/ UTRAN cells Optional Measurement Report Solicitation Redirection procedure RRC Connection Release to GERAN or UTRAN Location Update procedure Location Area Update or Combined RA/LA Update (if LAI from radio is different than the one stored by the UE CS Call Setup CS MO Call Establishment 20 Nokia Siemens Networks
MT call flow from LTE to GERAN/UTRAN with redirection UE/MS enb BSS/RNS MME MSC CS Paging RRC Connection Request RRC Connection Setup CS Paging CS Paging RRC Connection and Extended Service messages RRC Connection Setup Complete with Extended Service Request (MO CSFB) S1-AP message with CSFB and Emergency Indicators Optional Measurement Report Solicitation UE makes IRAT measurements from GERAN cells RRC Connection Release to GERAN or UTRAN Redirection procedure Paging Response A/Iu-cs message with paging response Paging Response Location Area Update or Combined RA/LA Update CS MT Call Establishment Location Update procedure CS Call Setup 21 Nokia Siemens Networks
FirstNet LTE with esrvcc to partner s 2/3G S3 is used for esrvcc with PS HO procedure (optional). Legacy SGSN requires MME to support Gn/Gp interface. Other VoLte functional elements: PCC/S/P-GW/P- CSCF/ATCF 22 Nokia Siemens Networks S5 LTE S1-U S6a HSS/ HLR MME Firstnet LTE S3 MAP Sv Roaming interfaces Partner s 2/3G network 2/3G SGSN GSM/WCDMA A BSC 2/3G MSC/VLR Iu-cs Gb/Iu-ps RNC To PSTN 2/3G SGSN
High level flow for E-UTRAN SRVCC UE E-UTRAN MME MSC Server Target UTRAN/GERAN 3GPP IMS VoLTE session ongoing SR VC C indication SR VC C possible indication Request to partner s 2/3G network via Sv interface Measurement Reports SRVCC Handover to UTRAN/GERAN required (CS or C S+PS) Initiates SRVCC for voice component Handles PS-PS HO for non-voice if needed CS handover preparation IMS Service C ontinuity Procedure Handover execution Handover CMD To eutra N Coordinates SRVCC an d PS HO resp o nse P S-CS HO response to MME (CS resources) 23 Nokia Siemens Networks
xample FirstNet VoLTE Solution Architecture E (MAP) 2G/3G Partner FirstNet 2G/3G CS MSS CS/IMS-MGW Nc (ISUP/BICC/SIP- I) Mc CS/IMS- MGW E (MAP) SMSC E (MAP) C (MAP) SGSN Sv,SGs CSFB/SRVCC/ MGCF/GMSC SIP TAS ISC/SIP HLR MME Gm/ SIP P-CSCF. BCF, ATCF Rx Mw/ SIP E/I/S-CSCF BGCF HSS SDM Gx PCRF Iq H.248 enb S/P-GW A-BGF ATGW MRFP 24 Nokia Siemens Networks
Thank you! 25 Nokia Siemens Networks