Presentation Slides
Permission to use with
attribution to ‘5G Americas’
is granted.

“We are still in the early stages and VoNR
will continue to develop and evolve along
with the evolution of 5G and beyond.”
Chris Pearson, President, 5G Americas

“We often forget that the mobile computer we carry
around in our pockets is still referred to as a ‘phone.’
Wireless networks were first designed for voice, and it
remains a critical real-time application today. Building a
network that can adapt is crucial in managing reliable,
high-quality and robust mobile voice services.”
David Krauss, Principal of Network
Architecture at Ciena

TMOBILE Quote

Figure shows the
general call flow of
EPSFB

Voice service and emergency
service in a 5G EN-DC

Early stage 5G SA device
with multiple VoLTE
options

Standard
VoNR device
features
Voice indication
in RRC
Connection
Request
Video
indication in
RRC
Connection
Request
Emergency
indication in RRC
Connection
Request
RTT (Real-time Text)
Call Accessibility
SPS SSAC Multiple DRBs
per PDU
Flow based QoS
5QI-1 DRB 5QI-5 DRB VoNR Capability
Bit
C-DRX
IFHO (Inter-
Frequency HO)
Service-based
IFHO
PSHO (IRAT HO) RoHC
RRC Re-
establishment
Short RLC SN PDCP SN TTI Bundling (slot
aggregation)
TDD FDD HO Xn-based HO 3GPP non-3GPP
HO
5G E911 Location
Limited Service Emergency
RRC
Always-On PDU

Example of 5G Use Case

High Level Architecture of VoLTE versus VoNR

High level architecture of EPS Fallback for Single Registration mode devices using the N26
interface

High level system architecture to
support SBA

High-level features that will
support the enablement of
VoNR or EPSFB
Feature Name Protocol Layer Purpose VoNR plan
Voice, video, emergency indication in RRC
Connection Request
RRC Call setup success rate optimization R15
SSAC RRC Call setup success rate optimization R15
Paging priority NGAP Call setup success rate optimization R15
Flow based QoS, GBR, PBR, LCP, DRB combinations MAC Basic function R15
SM signaling NGAP Basic function R15
SPS MAC Power/overhead optimization R15
C-DRX MAC Power optimization R15
TTI Bundling (slot aggregation) PHY Coverage optimization R15
Short RLC SN RLC Coverage/overhead optimization R15
RoHC PDCP Coverage/overhead optimization R15
ECN UP and IMS
Reliability and spectral efficiency
optimization
R15
MAC CE based rate adaption MAC
Reliability and spectral efficiency
optimization
R15
UE reporting air interface delay budget adjustment RRC
Power, voice quality and coverage
optimization
R15
SRVCC to UTRAN System Mobility optimization R16
MDT for MMTel RRC Network optimization R16
VoPS NAS Terminal Voice Capability Detection R15
P-CSCF Discovery and Transportation
NAS
Selection & Sharing of Proxy Server
details
R15
Paging Policy Differentiation for IMS NGAP Call setup success rate optimization R15
EMC/EMF Selection NAS Emergency Call handling mode R15
T-ADS for IMS Voice SBI/DIAMETER Domain Selection for Terminating call R15
UE capability match request NGAP Terminal Capability against RAN R15
IRAT to LTE with RWR (Release w Redirect) GPTV2/NGAP Mobility from NR to LTE R15
IRAT HO to LTE (aka. PS HO) GTPV2/NGAP Mobility from NR to LTE R15
Always-ON PDU Session for IMS NAS Call Setup SR & Optimization R15

Emergency Service Fallback Procedure (TS 23.502)

Supported
versions of
UE
positioning
methods (TS
38.305)
Method UE-based UE-assisted, LMF-
based
NG-RAN node
assisted
SUPL
A-GNSS Yes Yes No Yes
OTDOA
Note1, Note 2
No Yes No Yes
E-CID
Note 4
No Yes Yes Yes for E-UTRA
Sensor Yes Yes No No
WLAN Yes Yes No Yes
Bluetooth No Yes No No
TBS
Note 5
Yes Yes No Yes (MBS)
DL-TDOA Yes Yes No Yes
DL-AoD Yes Yes No Yes
Multi-RTT No Yes Yes Yes
NR E-CID No Yes Yes Yes (DL NR E-
CID)
UL-TDOA No No Yes Yes
UL-AoA No No Yes Yes
NOTE 1: This includes TBS positioning based on PRS signals.
NOTE 2: In this version of the specification only OTDOA based on LTE signals is supported.
NOTE 3: Void
NOTE 4: This includes Cell-ID for NR method.
NOTE 5: In this version of the specification only for TBS positioning based on MBS signals.
NOTE 6: Void

Sample Call Flow for
VoNR session
establishment
UE gNB PCF
AMF SMF UPF UDM
5G MM context has been established (UE registered with 5GCN); NAS Signaling Connection is established
SMF selection by AMF
Successful procedure for PDU Session Establishment setup would be followed by IMS REGISTRATION (not shown)
P-CSCF I/SCSCF
SIP INVITE
18x
18x
IMS Voice Session setup Flow
IMS signaling
Bearer
IMS Voice Bearer
(dedicated)
IMS Voice Bearer
(dedicated)
PDU session setup request from UE
for IMS DNN
SMF - Policy session setup with PCF
PDU session setup accepted
UPF selection by AMF
QFI-1 bearer setup as part of resource reservation
IMS Voice Session setup completion

Call flow depicting EPS
fallback

Conclusion from NGMN study on EPS FB performance

VPMN routing with
Local Breakout

4G/5G/IMS roaming
architecture