VoLTE - Voice over LTE (4G)
What is VoLTE?
VoLTE (Voice over LTE) is a technology that enables voice calls over the LTE (4G) data network instead of traditional circuit-switched networks. It uses the IP Multimedia Subsystem (IMS) to deliver voice, video, and messaging services over IP.
Why is VoLTE useful?
High-quality voice (HD Voice) with lower latency.
Simultaneous voice and data over LTE.
Efficient spectrum use by eliminating the need for fallback to 2G/3G.
Supports rich communication services (RCS) like video calling, file sharing, etc.
How it works?
Call Initiation: The UE (User Equipment) sends a SIP INVITE via IMS.
Session Setup: IMS core handles SIP signaling and negotiates media via SDP.
Bearer Setup: The EPC (Evolved Packet Core) sets up dedicated bearers for voice.
Call Management: SIP messages manage call progress, hold, transfer, etc.
Call Termination: SIP BYE ends the session, and bearers are released.
Where is VoLTE used?
4G LTE networks for voice and video calling.
IMS Core for managing multimedia sessions.
EPC (Evolved Packet Core) for bearer management.
RCS services for enhanced messaging and media sharing.
Which OSI layer does VoLTE belong to?
Layer 7 (Application) - SIP (Session Initiation Protocol), SDP (Session Description Protocol), RTP (Real-Time Transport Protocol)
Layer 6 (Presentation) - Codec negotiation (e.g., AMR-WB for HD Voice), media format handling
Layer 5 (Session) - SIP session control, call setup/teardown, registration
Layer 4 (Transport) - UDP (for SIP, RTP), TCP (for some IMS interfaces), SCTP (for Diameter)
Layer 3 (Network) - IP (IPv4/IPv6) for routing packets
Layer 2 (Data Link) - LTE MAC, RLC, PDCP layers
Layer 1 (Physical) - LTE PHY layer (radio transmission)
Topics in this section,
- ref:
VoLTE Feature : Roaming Support <VoLTE_step18>
In this section, you are going to learn
Terminology
Version Info
VoLTE Version |
VoLTE Number/3GPP Spec Number |
Year |
Core Idea / Contribution |
|---|---|---|---|
Release 8 |
TS 23.228, TS 24.229 |
2008 |
Introduced IMS architecture and SIP-based voice over LTE. |
Release 9 |
TS 23.203, TS 29.212 |
2009 |
Enhanced QoS and policy control for VoLTE via PCRF and PCC framework. |
Release 10 |
TS 23.401, TS 24.301 |
2011 |
Improved handover mechanisms and bearer management for seamless VoLTE experience. |
Release 11 |
TS 23.228, TS 29.214 |
2012 |
Introduced SRVCC (Single Radio Voice Call Continuity) for LTE to 3G/2G handover. |
Release 12 |
TS 29.949 |
2015 |
Defined VoLTE roaming scenarios and interworking with legacy networks 1. |
Release 13 |
TS 23.228, TS 24.229 |
2016 |
Introduced enhanced emergency services and support for IMS centralized services. |
Release 14+ |
Various |
2017+ |
Continued enhancements for VoLTE/VoNR, 5G integration, and mission-critical services. |
Setup
Setup
SIP INVITE Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
1 |
SIP INVITE Packet |
Initiates a VoLTE call session. Includes SDP for media negotiation. |
~500800 |
Request Line |
Contains the INVITE method and SIP URI. |
~2040 |
|
Headers |
Includes To, From, Call-ID, CSeq, Via, Contact, etc. |
~300400 |
|
SDP Body |
Describes media types, codecs (e.g., AMR-WB), and ports. |
~150300 |
SIP 200 OK Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
2 |
SIP 200 OK Packet |
Confirms successful call setup. Includes SDP response. |
~400700 |
Status Line |
Contains the response code and reason phrase. |
~2040 |
|
Headers |
Includes Via, To, From, Call-ID, CSeq, Contact, etc. |
~200300 |
|
SDP Body |
Confirms media session parameters. |
~150300 |
SIP ACK Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
3 |
SIP ACK Packet |
Acknowledges the 200 OK response. |
~200300 |
Request Line |
Contains the ACK method and SIP URI. |
~2040 |
|
Headers |
Includes To, From, Call-ID, CSeq, Via, etc. |
~150250 |
RTP Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
4 |
RTP Packet |
Carries encoded voice data (e.g., AMR-WB codec). |
~60100 (per packet) |
RTP Header |
Contains sequence number, timestamp, payload type. |
~12 |
|
Payload |
Encoded voice frame (AMR/AMR-WB). |
~2060 |
SIP BYE Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
5 |
SIP BYE Packet |
Terminates the call session. |
~200300 |
Request Line |
Contains the BYE method and SIP URI. |
~2040 |
|
Headers |
Includes To, From, Call-ID, CSeq, Via, etc. |
~150250 |
Bearer Setup (S1-AP) Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
6 |
Bearer Setup (S1-AP) |
Establishes dedicated bearer for VoLTE call via MME and eNodeB. |
~100300 |
Initial Context Setup |
Includes QoS parameters, bearer ID, and NAS signaling. |
~100200 |
|
E-RAB Setup Request |
Requests bearer creation with specific QoS. |
~50100 |
Diameter (Gx/gy/Cx) Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
7 |
Diameter (Gx/Gy/Cx) |
Used for policy control (PCRF), charging, and subscriber profile management. |
~5001000+ |
CCR/CCA (Credit Control) |
Used for prepaid billing and quota management. |
~300600 |
|
AAR/AAA (Auth/Authorization) |
Used for IMS registration and service authorization. |
~300500 |
S.no |
Use Case |
Description |
|---|---|---|
1 |
HD Voice Calls |
Provides high-definition voice quality using AMR-WB codec over LTE. |
2 |
Simultaneous Voice and Data |
Allows users to talk and use mobile data at the same time without fallback. |
3 |
Video Calling over LTE |
Enables real-time video communication using IMS and RTP. |
4 |
VoLTE Roaming |
Supports voice services while roaming internationally over LTE networks. |
5 |
Emergency Calling (eCall) |
Offers prioritized and location-aware emergency services over LTE. |
6 |
Rich Communication Services |
Supports messaging, file sharing, and presence info via RCS over IMS. |
7 |
Battery Efficiency |
Reduces power consumption compared to CSFB (Circuit Switched Fallback). |
8 |
Faster Call Setup |
Establishes calls more quickly than legacy 2G/3G networks. |
9 |
Interworking with Legacy Networks |
Enables seamless handover to 2G/3G via SRVCC when LTE coverage is lost. |
10 |
Policy and Charging Control |
Integrates with PCRF for real-time QoS and billing management. |
S.no |
Feature |
Description |
|---|---|---|
1 |
High-Definition (HD) Voice |
Uses AMR-WB codec for superior voice clarity and natural sound. |
2 |
All-IP Architecture |
Operates entirely over IP using IMS, eliminating circuit-switched fallback. |
3 |
Fast Call Setup |
Reduces call setup time compared to 2G/3G networks. |
4 |
Simultaneous Voice & Data |
Allows voice calls and internet usage at the same time over LTE. |
5 |
Improved Battery Life |
More efficient than CSFB, reducing radio switching and power usage. |
6 |
Seamless Handover (SRVCC) |
Maintains call continuity when moving from LTE to 2G/3G networks. |
7 |
QoS Support |
Ensures voice quality through dedicated bearers and policy control. |
8 |
Emergency Services Support |
Enables location-aware emergency calling (e.g., eCall). |
9 |
IMS-Based Services |
Supports rich communication services like video calling, chat, and file share. |
10 |
Roaming Support |
Enables VoLTE calls while roaming with compatible networks and IMS interconnect. |
High-Defnition (HD) Voice - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
Call between VoLTE devices |
Both support AMR-WB |
HD voice enabled |
2 |
Call from VoLTE to 3G |
3G does not support AMR-WB |
Falls back to narrowband |
3 |
Call from VoLTE to PSTN |
Landline does not support AMR-WB |
Falls back to narrowband |
4 |
Call from VoLTE to VoWiFi |
Both support AMR-WB |
HD voice enabled |
5 |
Call from VoLTE to VoNR |
Both support HD codecs |
HD voice enabled |
6 |
Call with poor LTE signal |
Low bandwidth |
Codec adapts to lower bitrate |
7 |
Call with strong LTE signal |
High bandwidth |
Full AMR-WB quality |
8 |
Call with background noise |
Use noise suppression |
Clear voice maintained |
9 |
Call in quiet environment |
No interference |
Natural voice quality |
10 |
Call with headset |
Wired or Bluetooth |
HD voice preserved |
11 |
Call with speakerphone |
Hands-free mode |
HD voice preserved |
12 |
Call with VoLTE disabled |
Use fallback network |
HD voice not available |
13 |
Call with airplane mode |
LTE disabled |
Call fails |
14 |
Call with AMR-WB disabled |
Use AMR-NB |
Narrowband voice |
15 |
Call with AMR-WB enabled |
Use full codec |
HD voice enabled |
16 |
Call with codec negotiation |
AMR-WB preferred |
HD voice selected |
17 |
Call with codec mismatch |
One side lacks AMR-WB |
Falls back to compatible codec |
18 |
Call with VoLTE roaming |
Roaming partner supports AMR-WB |
HD voice enabled |
19 |
Call with VoLTE roaming |
Roaming partner lacks AMR-WB |
Narrowband voice |
20 |
Call with dual SIM |
VoLTE active on one SIM |
HD voice on active SIM |
21 |
Call with VoLTE on 5G NSA |
LTE used for voice |
HD voice enabled |
22 |
Call with VoLTE on 5G SA |
EPS fallback used |
HD voice enabled |
23 |
Call with VoLTE on 4G-only phone |
No fallback |
HD voice enabled |
24 |
Call with VoLTE on 2G/3G-only phone |
No LTE |
HD voice not available |
25 |
Call with VoLTE on Android |
AMR-WB supported |
HD voice enabled |
26 |
Call with VoLTE on iOS |
AMR-WB supported |
HD voice enabled |
27 |
Call with VoLTE on feature phone |
AMR-WB supported |
HD voice enabled |
28 |
Call with VoLTE on smartwatch |
LTE-enabled watch |
HD voice enabled |
29 |
Call with VoLTE on tablet |
LTE-enabled tablet |
HD voice enabled |
30 |
Call with VoLTE on car system |
LTE modem in vehicle |
HD voice enabled |
31 |
Call with VoLTE on VoIP gateway |
AMR-WB passthrough |
HD voice preserved |
32 |
Call with VoLTE on SIP trunk |
AMR-WB supported |
HD voice enabled |
33 |
Call with VoLTE on IMS core |
Codec negotiation successful |
HD voice enabled |
34 |
Call with VoLTE on VPN |
Encrypted LTE tunnel |
HD voice preserved |
35 |
Call with VoLTE on congested network |
Codec adapts |
Voice quality maintained |
36 |
Call with VoLTE on QoS-enabled LTE |
Prioritized traffic |
HD voice preserved |
37 |
Call with VoLTE on non-QoS LTE |
Best-effort traffic |
Possible degradation |
38 |
Call with VoLTE on VoNR fallback |
LTE used for voice |
HD voice enabled |
39 |
Call with VoLTE on airplane Wi-Fi |
No LTE |
Call fails |
40 |
Call with VoLTE on satellite LTE |
High latency |
HD voice may degrade |
41 |
Call with VoLTE on private LTE |
Enterprise network |
HD voice enabled |
42 |
Call with VoLTE on CBRS LTE |
Shared spectrum |
HD voice enabled |
43 |
Call with VoLTE on LTE-M |
IoT-focused LTE |
HD voice not supported |
44 |
Call with VoLTE on NB-IoT |
Narrowband IoT |
HD voice not supported |
45 |
Call with VoLTE on LTE Cat-1 |
Full voice support |
HD voice enabled |
46 |
Call with VoLTE on LTE Cat-0 |
Limited support |
HD voice may not be available |
47 |
Call with VoLTE on LTE Cat-6 |
Carrier aggregation |
HD voice enabled |
48 |
Call with VoLTE on LTE Cat-16 |
Gigabit LTE |
HD voice enabled |
49 |
Call with VoLTE on test simulator |
Lab environment |
HD voice verified |
50 |
Call with VoLTE on real network |
Field test |
HD voice confirmed |
All-IP Architecture - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
Call between VoLTE devices |
Both support AMR-WB |
HD voice enabled |
2 |
Call from VoLTE to 3G |
3G does not support AMR-WB |
Falls back to narrowband |
3 |
Call from VoLTE to PSTN |
Landline does not support AMR-WB |
Falls back to narrowband |
4 |
Call from VoLTE to VoWiFi |
Both support AMR-WB |
HD voice enabled |
5 |
Call from VoLTE to VoNR |
Both support HD codecs |
HD voice enabled |
6 |
Call with poor LTE signal |
Low bandwidth |
Codec adapts to lower bitrate |
7 |
Call with strong LTE signal |
High bandwidth |
Full AMR-WB quality |
8 |
Call with background noise |
Use noise suppression |
Clear voice maintained |
9 |
Call in quiet environment |
No interference |
Natural voice quality |
10 |
Call with headset |
Wired or Bluetooth |
HD voice preserved |
11 |
Call with speakerphone |
Hands-free mode |
HD voice preserved |
12 |
Call with VoLTE disabled |
Use fallback network |
HD voice not available |
13 |
Call with airplane mode |
LTE disabled |
Call fails |
14 |
Call with AMR-WB disabled |
Use AMR-NB |
Narrowband voice |
15 |
Call with AMR-WB enabled |
Use full codec |
HD voice enabled |
16 |
Call with codec negotiation |
AMR-WB preferred |
HD voice selected |
17 |
Call with codec mismatch |
One side lacks AMR-WB |
Falls back to compatible codec |
18 |
Call with VoLTE roaming |
Roaming partner supports AMR-WB |
HD voice enabled |
19 |
Call with VoLTE roaming |
Roaming partner lacks AMR-WB |
Narrowband voice |
20 |
Call with dual SIM |
VoLTE active on one SIM |
HD voice on active SIM |
21 |
Call with VoLTE on 5G NSA |
LTE used for voice |
HD voice enabled |
22 |
Call with VoLTE on 5G SA |
EPS fallback used |
HD voice enabled |
23 |
Call with VoLTE on 4G-only phone |
No fallback |
HD voice enabled |
24 |
Call with VoLTE on 2G/3G-only phone |
No LTE |
HD voice not available |
25 |
Call with VoLTE on Android |
AMR-WB supported |
HD voice enabled |
26 |
Call with VoLTE on iOS |
AMR-WB supported |
HD voice enabled |
27 |
Call with VoLTE on feature phone |
AMR-WB supported |
HD voice enabled |
28 |
Call with VoLTE on smartwatch |
LTE-enabled watch |
HD voice enabled |
29 |
Call with VoLTE on tablet |
LTE-enabled tablet |
HD voice enabled |
30 |
Call with VoLTE on car system |
LTE modem in vehicle |
HD voice enabled |
31 |
Call with VoLTE on VoIP gateway |
AMR-WB passthrough |
HD voice preserved |
32 |
Call with VoLTE on SIP trunk |
AMR-WB supported |
HD voice enabled |
33 |
Call with VoLTE on IMS core |
Codec negotiation successful |
HD voice enabled |
34 |
Call with VoLTE on VPN |
Encrypted LTE tunnel |
HD voice preserved |
35 |
Call with VoLTE on congested network |
Codec adapts |
Voice quality maintained |
36 |
Call with VoLTE on QoS-enabled LTE |
Prioritized traffic |
HD voice preserved |
37 |
Call with VoLTE on non-QoS LTE |
Best-effort traffic |
Possible degradation |
38 |
Call with VoLTE on VoNR fallback |
LTE used for voice |
HD voice enabled |
39 |
Call with VoLTE on airplane Wi-Fi |
No LTE |
Call fails |
40 |
Call with VoLTE on satellite LTE |
High latency |
HD voice may degrade |
41 |
Call with VoLTE on private LTE |
Enterprise network |
HD voice enabled |
42 |
Call with VoLTE on CBRS LTE |
Shared spectrum |
HD voice enabled |
43 |
Call with VoLTE on LTE-M |
IoT-focused LTE |
HD voice not supported |
44 |
Call with VoLTE on NB-IoT |
Narrowband IoT |
HD voice not supported |
45 |
Call with VoLTE on LTE Cat-1 |
Full voice support |
HD voice enabled |
46 |
Call with VoLTE on LTE Cat-0 |
Limited support |
HD voice may not be available |
47 |
Call with VoLTE on LTE Cat-6 |
Carrier aggregation |
HD voice enabled |
48 |
Call with VoLTE on LTE Cat-16 |
Gigabit LTE |
HD voice enabled |
49 |
Call with VoLTE on test simulator |
Lab environment |
HD voice verified |
50 |
Call with VoLTE on real network |
Field test |
HD voice confirmed |
Fast Call Setup - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
VoLTE call setup time < 2G |
Compare with GSM |
VoLTE setup faster |
2 |
VoLTE call setup time < 3G |
Compare with UMTS |
VoLTE setup faster |
3 |
VoLTE call setup under 2s |
Measure setup time |
< 2 seconds |
4 |
VoLTE call setup under 1.5s |
Optimized network |
< 1.5 seconds |
5 |
VoLTE call setup with strong signal |
Full LTE coverage |
Fast setup |
6 |
VoLTE call setup with weak signal |
Low LTE signal |
Slight delay |
7 |
VoLTE call setup with QoS |
Dedicated bearer |
Fast setup |
8 |
VoLTE call setup without QoS |
Best-effort bearer |
Slightly slower |
9 |
VoLTE call setup with IMS pre-registered |
IMS ready |
Instant setup |
10 |
VoLTE call setup with IMS registration delay |
IMS not ready |
Setup delayed |
11 |
VoLTE call setup with SIP pre-established |
SIP session cached |
Fast setup |
12 |
VoLTE call setup with SIP DNS delay |
Slow DNS resolution |
Setup delayed |
13 |
VoLTE call setup with SIP compression |
SigComp enabled |
Faster signaling |
14 |
VoLTE call setup with SIP over TCP |
Reliable transport |
Slightly slower |
15 |
VoLTE call setup with SIP over UDP |
Faster transport |
Fast setup |
16 |
VoLTE call setup with IPv6 |
Dual-stack network |
Fast setup |
17 |
VoLTE call setup with IPv4 |
Legacy IP |
Fast setup |
18 |
VoLTE call setup with NAT traversal |
Behind NAT |
Setup successful |
19 |
VoLTE call setup with roaming |
Home IMS used |
Setup time acceptable |
20 |
VoLTE call setup with local breakout |
Visited IMS used |
Fast setup |
21 |
VoLTE call setup with SRVCC disabled |
No fallback |
Fast setup |
22 |
VoLTE call setup with SRVCC enabled |
Fallback supported |
Setup time unaffected |
23 |
VoLTE call setup with ePDG |
Over Wi-Fi |
Setup successful |
24 |
VoLTE call setup with LTE handover |
During mobility |
Setup time stable |
25 |
VoLTE call setup with 5G NSA |
LTE used for voice |
Fast setup |
26 |
VoLTE call setup with 5G SA fallback |
EPS fallback |
Setup time slightly increased |
27 |
VoLTE call setup with dual SIM |
VoLTE active SIM |
Fast setup |
28 |
VoLTE call setup with airplane mode toggle |
LTE re-enabled |
Setup resumes |
29 |
VoLTE call setup with call forwarding |
IMS handles redirection |
Fast setup |
30 |
VoLTE call setup with call barring |
IMS blocks call |
Setup fails quickly |
31 |
VoLTE call setup with call waiting |
IMS manages queue |
Setup successful |
32 |
VoLTE call setup with call hold/resume |
SIP re-INVITE used |
Fast transition |
33 |
VoLTE call setup with emergency call |
IMS emergency support |
Fast setup |
34 |
VoLTE call setup with codec negotiation |
AMR-WB selected |
Setup time unaffected |
35 |
VoLTE call setup with network congestion |
High traffic |
Slight delay |
36 |
VoLTE call setup with IMS failover |
Backup IMS used |
Setup successful |
37 |
VoLTE call setup with IMS load balancing |
Distributed signaling |
Fast setup |
38 |
VoLTE call setup with SIP retry |
Initial failure |
Setup successful on retry |
39 |
VoLTE call setup with SIP OPTIONS ping |
IMS reachable |
Fast setup |
40 |
VoLTE call setup with SIP 100 Trying |
Immediate response |
Setup continues |
41 |
VoLTE call setup with SIP 180 Ringing |
Early media supported |
Setup confirmed |
42 |
VoLTE call setup with SIP 200 OK |
Final response |
Call connected |
43 |
VoLTE call setup with SIP CANCEL |
User cancels call |
Setup aborted |
44 |
VoLTE call setup with IMS over TLS |
Secure signaling |
Slight delay |
45 |
VoLTE call setup with IMS over IPSec |
Secure media |
Setup time stable |
46 |
VoLTE call setup with IMS registration timer |
Re-registration active |
Setup unaffected |
47 |
VoLTE call setup with IMS deregistration |
IMS lost |
Setup fails |
48 |
VoLTE call setup with test simulator |
Lab environment |
Setup time measured |
49 |
VoLTE call setup with real network |
Field test |
Setup time < 2s |
50 |
VoLTE call setup with legacy fallback disabled |
LTE-only device |
Setup successful |
Simulataneous Voice & Data - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
Make VoLTE call and browse web |
Open browser during call |
Web page loads |
2 |
Make VoLTE call and stream video |
Play YouTube during call |
Video plays smoothly |
3 |
Make VoLTE call and use GPS |
Use Google Maps during call |
Navigation works |
4 |
Make VoLTE call and send email |
Compose and send email |
Email sent successfully |
5 |
Make VoLTE call and use WhatsApp |
Send message during call |
Message delivered |
6 |
Make VoLTE call and upload file |
Upload to cloud |
Upload continues |
7 |
Make VoLTE call and download file |
Download large file |
Download continues |
8 |
Make VoLTE call and use hotspot |
Share LTE via hotspot |
Other device connects |
9 |
Make VoLTE call and use VPN |
VPN active during call |
Both work simultaneously |
10 |
Make VoLTE call and use banking app |
Perform transaction |
Transaction successful |
11 |
Make VoLTE call and use social media |
Scroll Instagram |
Feed loads |
12 |
Make VoLTE call and use video call app |
Open Zoom during call |
App opens, audio paused |
13 |
Make VoLTE call and use camera upload |
Auto-upload photos |
Upload continues |
14 |
Make VoLTE call and use smart home app |
Control IoT device |
Command sent |
15 |
Make VoLTE call and use cloud sync |
Sync files to cloud |
Sync continues |
16 |
Make VoLTE call and use music streaming |
Play Spotify |
Music plays |
17 |
Make VoLTE call and use messaging app |
Use Telegram |
Messages sent |
18 |
Make VoLTE call and use ride-hailing app |
Book Uber |
Booking successful |
19 |
Make VoLTE call and use food delivery app |
Order food |
Order placed |
20 |
Make VoLTE call and use health app |
Sync fitness data |
Sync successful |
21 |
Make VoLTE call and use smart watch |
LTE watch syncs |
Data syncs |
22 |
Make VoLTE call and use tethering |
Laptop uses LTE |
Internet works |
23 |
Make VoLTE call and use cloud gaming |
Play game on GeForce Now |
Game runs |
24 |
Make VoLTE call and use AR app |
Use AR navigation |
Works during call |
25 |
Make VoLTE call and use translation app |
Translate voice |
App functions |
26 |
Make VoLTE call and use voice assistant |
Ask Google Assistant |
Response received |
27 |
Make VoLTE call and use weather app |
Check forecast |
Data loads |
28 |
Make VoLTE call and use stock app |
View live prices |
Prices update |
29 |
Make VoLTE call and use news app |
Read news |
Articles load |
30 |
Make VoLTE call and use podcast app |
Stream podcast |
Audio plays |
31 |
Make VoLTE call and use cloud IDE |
Code in browser |
IDE responsive |
32 |
Make VoLTE call and use email sync |
Background sync |
Emails received |
33 |
Make VoLTE call and use calendar sync |
Calendar updates |
Sync successful |
34 |
Make VoLTE call and use smart TV remote |
Control TV via app |
Commands work |
35 |
Make VoLTE call and use smart car app |
Start car remotely |
Command sent |
36 |
Make VoLTE call and use payment app |
Tap to pay |
Payment successful |
37 |
Make VoLTE call and use file manager |
Access cloud files |
Files open |
38 |
Make VoLTE call and use remote desktop |
Connect to PC |
Session active |
39 |
Make VoLTE call and use screen sharing |
Share screen via app |
Works during call |
40 |
Make VoLTE call and use online test |
Take exam in browser |
Test continues |
41 |
Make VoLTE call and use e-learning app |
Watch lecture |
Video plays |
42 |
Make VoLTE call and use e-reader |
Download book |
Book opens |
43 |
Make VoLTE call and use online banking |
Check balance |
Info loads |
44 |
Make VoLTE call and use smart lock app |
Unlock door |
Command sent |
45 |
Make VoLTE call and use smart light app |
Toggle lights |
Lights respond |
46 |
Make VoLTE call and use smart thermostat |
Adjust temperature |
Change applied |
47 |
Make VoLTE call and use smart camera |
View live feed |
Video streams |
48 |
Make VoLTE call and use smart speaker |
Control via app |
Speaker responds |
49 |
Make VoLTE call and use cloud backup |
Backup photos |
Continues during call |
50 |
Make VoLTE call and use mobile banking |
Transfer funds |
Transaction completes |
Improved Battery Life - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
VoLTE call vs CSFB call |
Compare battery drain |
VoLTE uses less power |
2 |
VoLTE call duration 10 min |
Measure battery usage |
Lower than CSFB |
3 |
VoLTE call duration 30 min |
Measure battery usage |
Lower than CSFB |
4 |
VoLTE call with LTE-only |
No fallback |
Efficient power usage |
5 |
CSFB call with 3G fallback |
Switch to 3G |
Higher power usage |
6 |
VoLTE call with background data |
LTE active |
Efficient usage |
7 |
CSFB call with background data |
Switch to 3G |
Data paused |
8 |
VoLTE call with screen off |
Measure standby drain |
Minimal drain |
9 |
VoLTE call with screen on |
Measure active drain |
Moderate drain |
10 |
VoLTE call with Bluetooth headset |
Measure power |
Efficient usage |
11 |
VoLTE call with Wi-Fi on |
LTE used for voice |
No extra drain |
12 |
VoLTE call with GPS active |
LTE handles both |
Efficient usage |
13 |
VoLTE call with app sync |
Background sync allowed |
No extra switching |
14 |
VoLTE call with music streaming |
LTE handles both |
Efficient usage |
15 |
VoLTE call with video streaming |
LTE handles both |
Efficient usage |
16 |
VoLTE call with hotspot active |
LTE shared |
Battery usage stable |
17 |
VoLTE call with VPN active |
LTE tunnel maintained |
Efficient usage |
18 |
VoLTE call with low signal |
LTE maintained |
Slight increase in drain |
19 |
VoLTE call with strong signal |
LTE stable |
Minimal drain |
20 |
VoLTE call with handover to 5G |
EPS fallback |
Battery usage stable |
21 |
VoLTE call with handover to Wi-Fi |
Switch to VoWiFi |
Battery usage reduced |
22 |
VoLTE call with airplane mode toggle |
LTE re-enabled |
Battery usage resumes |
23 |
VoLTE call with dual SIM |
VoLTE active SIM |
Efficient usage |
24 |
VoLTE call with roaming |
LTE roaming |
Battery usage stable |
25 |
VoLTE call with SRVCC disabled |
No fallback |
Battery usage optimized |
26 |
VoLTE call with SRVCC enabled |
Fallback to 3G |
Slight increase in drain |
27 |
VoLTE call with IMS pre-registered |
No extra signaling |
Efficient usage |
28 |
VoLTE call with IMS re-registration |
Mid-call |
Slight increase in drain |
29 |
VoLTE call with SIP retry |
Initial failure |
Retry consumes power |
30 |
VoLTE call with SIP compression |
Reduced signaling |
Battery usage optimized |
31 |
VoLTE call with codec negotiation |
AMR-WB selected |
Efficient processing |
32 |
VoLTE call with QoS bearer |
Dedicated LTE path |
Efficient usage |
33 |
VoLTE call with best-effort bearer |
No QoS |
Slight increase in drain |
34 |
VoLTE call with LTE Cat-4 |
Standard LTE |
Efficient usage |
35 |
VoLTE call with LTE Cat-6 |
Carrier aggregation |
Battery usage stable |
36 |
VoLTE call with LTE Cat-16 |
Gigabit LTE |
Efficient usage |
37 |
VoLTE call with LTE-M |
IoT LTE |
VoLTE not supported |
38 |
VoLTE call with NB-IoT |
Narrowband LTE |
VoLTE not supported |
39 |
VoLTE call with smart watch |
LTE-enabled wearable |
Efficient usage |
40 |
VoLTE call with tablet |
LTE-enabled tablet |
Battery usage optimized |
41 |
VoLTE call with car system |
LTE modem in vehicle |
Efficient usage |
42 |
VoLTE call with smart home hub |
LTE-enabled hub |
Battery usage stable |
43 |
VoLTE call with smart speaker |
LTE-enabled speaker |
Efficient usage |
44 |
VoLTE call with smart TV |
LTE-enabled TV |
Battery usage optimized |
45 |
VoLTE call with IoT gateway |
LTE-enabled gateway |
Efficient usage |
46 |
VoLTE call with test simulator |
Lab test |
Battery usage measured |
47 |
VoLTE call with real network |
Field test |
Battery usage confirmed |
48 |
VoLTE call with power monitoring app |
Use GSam Battery Monitor |
VoLTE more efficient |
49 |
VoLTE call with thermal monitoring |
Check device heat |
Lower than CSFB |
50 |
VoLTE call with battery log |
Compare logs over time |
VoLTE shows better efficiency |
Seamless Handover (SRVCC) - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
VoLTE call with SRVCC enabled |
Move from LTE to 3G |
Call continues |
2 |
VoLTE call with SRVCC disabled |
Move from LTE to 3G |
Call drops |
3 |
VoLTE call with LTE to 2G handover |
SRVCC active |
Call continues |
4 |
VoLTE call with LTE to 3G handover |
SRVCC active |
Call continues |
5 |
VoLTE call with LTE to no coverage |
No fallback |
Call drops |
6 |
VoLTE call with LTE to Wi-Fi |
VoWiFi not supported |
Call drops |
7 |
VoLTE call with LTE to VoWiFi |
VoWiFi supported |
Call continues |
8 |
VoLTE call with fast mobility |
Driving at 100 km/h |
Call continues |
9 |
VoLTE call with slow mobility |
Walking speed |
Call continues |
10 |
VoLTE call with SRVCC to 2G |
GSM fallback |
Call continues |
11 |
VoLTE call with SRVCC to 3G |
UMTS fallback |
Call continues |
12 |
VoLTE call with SRVCC to CDMA |
CDMA fallback |
Call continues (if supported) |
13 |
VoLTE call with SRVCC to HSPA |
HSPA fallback |
Call continues |
14 |
VoLTE call with SRVCC to EDGE |
EDGE fallback |
Call continues |
15 |
VoLTE call with SRVCC to GPRS |
GPRS fallback |
Call continues |
16 |
VoLTE call with SRVCC and poor LTE |
LTE signal drops |
Call continues on 3G |
17 |
VoLTE call with SRVCC and poor 3G |
Handover fails |
Call drops |
18 |
VoLTE call with SRVCC and good 3G |
Seamless transition |
Call continues |
19 |
VoLTE call with SRVCC and IMS active |
IMS session maintained |
Call continues |
20 |
VoLTE call with SRVCC and IMS inactive |
IMS not available |
Call drops |
21 |
VoLTE call with SRVCC and SIP re-INVITE |
Mid-call update |
Call continues |
22 |
VoLTE call with SRVCC and codec change |
AMR-WB to AMR-NB |
Call continues |
23 |
VoLTE call with SRVCC and QoS change |
LTE to 3G bearer |
Call continues |
24 |
VoLTE call with SRVCC and call hold |
Call held during handover |
Call resumes |
25 |
VoLTE call with SRVCC and call transfer |
Transfer during handover |
Call completes |
26 |
VoLTE call with SRVCC and call waiting |
Incoming call during handover |
Call managed |
27 |
VoLTE call with SRVCC and call forwarding |
Forwarded during handover |
Call redirected |
28 |
VoLTE call with SRVCC and emergency call |
112/911 call |
Handover supported |
29 |
VoLTE call with SRVCC and dual SIM |
Active SIM supports SRVCC |
Call continues |
30 |
VoLTE call with SRVCC and roaming |
Roaming partner supports SRVCC |
Call continues |
31 |
VoLTE call with SRVCC and no roaming support |
No SRVCC in visited network |
Call drops |
32 |
VoLTE call with SRVCC and IMS re-registration |
During handover |
Call continues |
33 |
VoLTE call with SRVCC and SIP session refresh |
During handover |
Call continues |
34 |
VoLTE call with SRVCC and handover delay |
Delay < 300ms |
Call continues |
35 |
VoLTE call with SRVCC and handover delay > 1s |
Delay too long |
Call drops |
36 |
VoLTE call with SRVCC and network congestion |
LTE congested |
Call continues on 3G |
37 |
VoLTE call with SRVCC and battery saver mode |
Device limits background tasks |
Call continues |
38 |
VoLTE call with SRVCC and airplane mode toggle |
LTE disabled |
Call drops |
39 |
VoLTE call with SRVCC and IMS failover |
IMS switches to backup |
Call continues |
40 |
VoLTE call with SRVCC and SIP error |
SIP 4xx/5xx |
Call drops |
41 |
VoLTE call with SRVCC and device reboot |
Mid-call |
Call drops |
42 |
VoLTE call with SRVCC and network reboot |
eNodeB reset |
Call drops |
43 |
VoLTE call with SRVCC and handover to femtocell |
3G femtocell |
Call continues |
44 |
VoLTE call with SRVCC and handover to macrocell |
3G macrocell |
Call continues |
45 |
VoLTE call with SRVCC and IMS deregistration |
Mid-call |
Call drops |
46 |
VoLTE call with SRVCC and call recording |
Recording continues |
Seamless |
47 |
VoLTE call with SRVCC and call encryption |
Secure call |
Encryption maintained |
48 |
VoLTE call with SRVCC and call analytics |
Handover logged |
Data captured |
49 |
VoLTE call with SRVCC and test simulator |
Lab test |
Handover verified |
50 |
VoLTE call with SRVCC and real network |
Field test |
Seamless handover confirmed |
QoS Support - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
VoLTE call with dedicated bearer |
EPS bearer established |
Voice prioritized |
2 |
VoLTE call with default bearer only |
No dedicated bearer |
Voice quality degraded |
3 |
VoLTE call with QoS Class Identifier (QCI) 1 |
Real-time voice |
Low latency |
4 |
VoLTE call with incorrect QCI |
Wrong QoS class |
Call setup fails or degrades |
5 |
VoLTE call with GBR bearer |
Guaranteed Bit Rate active |
Consistent voice quality |
6 |
VoLTE call with non-GBR bearer |
Best-effort traffic |
Voice may degrade |
7 |
VoLTE call with PCRF active |
Policy control enabled |
QoS enforced |
8 |
VoLTE call with PCRF failure |
Policy server down |
QoS fallback or failure |
9 |
VoLTE call with PCEF enforcement |
QoS rules applied |
Voice prioritized |
10 |
VoLTE call with APN QoS profile |
Correct APN settings |
QoS applied |
11 |
VoLTE call with bearer preemption |
Lower priority bearer dropped |
VoLTE call preserved |
12 |
VoLTE call with congestion |
Competing traffic |
Voice quality maintained |
13 |
VoLTE call with handover |
LTE to 3G |
QoS maintained via SRVCC |
14 |
VoLTE call with Wi-Fi offload |
VoWiFi active |
QoS maintained |
15 |
VoLTE call with ePDG tunnel |
Secure IPsec tunnel |
QoS preserved |
16 |
VoLTE call with IMS registration |
IMS QoS profile applied |
Voice prioritized |
17 |
VoLTE call with SIP signaling |
SIP packets prioritized |
Fast call setup |
18 |
VoLTE call with RTP media |
RTP packets prioritized |
Low jitter |
19 |
VoLTE call with jitter buffer |
Buffer active |
Smooth audio |
20 |
VoLTE call with packet loss |
Network drops packets |
Voice quality degrades gracefully |
21 |
VoLTE call with latency < 150ms |
Ideal conditions |
Excellent voice quality |
22 |
VoLTE call with latency > 300ms |
High delay |
Voice quality degraded |
23 |
VoLTE call with QoS monitoring |
Real-time stats |
Metrics logged |
24 |
VoLTE call with QoS alarms |
Threshold exceeded |
Alert triggered |
25 |
VoLTE call with QoS KPIs |
Monitor MOS, jitter, delay |
Within acceptable range |
26 |
VoLTE call with QoS policy update |
Mid-call change |
QoS adjusted |
27 |
VoLTE call with QoS downgrade |
Network congestion |
Voice still functional |
28 |
VoLTE call with QoS upgrade |
Bandwidth available |
Voice quality improves |
29 |
VoLTE call with QoS on roaming |
Visited network supports QoS |
Voice quality maintained |
30 |
VoLTE call with QoS on home network |
Full support |
Optimal voice quality |
31 |
VoLTE call with QoS on dual SIM |
Active SIM prioritized |
QoS applied |
32 |
VoLTE call with QoS on 5G NSA |
LTE used for voice |
QoS maintained |
33 |
VoLTE call with QoS on 5G SA |
EPS fallback |
QoS preserved |
34 |
VoLTE call with QoS on private LTE |
Enterprise network |
QoS enforced |
35 |
VoLTE call with QoS on CBRS |
Shared spectrum |
QoS maintained |
36 |
VoLTE call with QoS on test simulator |
Lab test |
QoS verified |
37 |
VoLTE call with QoS on real network |
Field test |
QoS confirmed |
38 |
VoLTE call with QoS in tunnel mode |
VPN active |
QoS preserved |
39 |
VoLTE call with QoS in split bearer |
Dual path |
QoS maintained |
40 |
VoLTE call with QoS in multi-access |
LTE + Wi-Fi |
QoS balanced |
41 |
VoLTE call with QoS in degraded LTE |
Weak signal |
Voice still clear |
42 |
VoLTE call with QoS in high-speed mobility |
Fast handover |
QoS preserved |
43 |
VoLTE call with QoS in airplane mode toggle |
LTE re-enabled |
QoS re-established |
44 |
VoLTE call with QoS in IMS failover |
Backup IMS used |
QoS maintained |
45 |
VoLTE call with QoS in SIP retry |
Signaling delay |
QoS re-applied |
46 |
VoLTE call with QoS in emergency call |
Priority override |
QoS guaranteed |
47 |
VoLTE call with QoS in group call |
Multiple users |
QoS shared |
48 |
VoLTE call with QoS in conference call |
Multi-party |
QoS maintained |
49 |
VoLTE call with QoS in call transfer |
Mid-call switch |
QoS preserved |
50 |
VoLTE call with QoS in call recording |
Media mirrored |
QoS unaffected |
Emergency Services Support - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
Dial 112 on VoLTE |
Emergency number |
Call connects immediately |
2 |
Dial 911 on VoLTE |
Emergency number |
Call connects immediately |
3 |
Emergency call with GPS enabled |
Location available |
Location sent to PSAP |
4 |
Emergency call with GPS disabled |
No location |
Network-based location used |
5 |
Emergency call with eCall system |
In-vehicle crash detected |
Call auto-initiated |
6 |
Emergency call with manual eCall |
Driver presses SOS |
Call initiated |
7 |
Emergency call with VoLTE only device |
No CS fallback |
Call connects via IMS |
8 |
Emergency call with no SIM |
SIM-less emergency call |
Call allowed |
9 |
Emergency call with locked phone |
Screen locked |
Call allowed |
10 |
Emergency call with airplane mode |
LTE re-enabled |
Call connects |
11 |
Emergency call with IMS registered |
IMS active |
Call routed via IMS |
12 |
Emergency call with IMS not registered |
IMS fallback |
Emergency IMS registration |
13 |
Emergency call with VoWiFi |
Wi-Fi available |
Call routed via ePDG |
14 |
Emergency call with no network |
No LTE or Wi-Fi |
Call fails |
15 |
Emergency call with location spoofing |
Tampered GPS |
Network location used |
16 |
Emergency call with location accuracy < 50m |
GPS fix |
Accurate location sent |
17 |
Emergency call with location accuracy > 500m |
Weak GPS |
Warning logged |
18 |
Emergency call with AGPS |
Assisted GPS used |
Fast location fix |
19 |
Emergency call with cell ID |
No GPS |
Cell-based location sent |
20 |
Emergency call with Wi-Fi positioning |
Indoor location |
Location sent |
21 |
Emergency call with hybrid location |
GPS + Wi-Fi + Cell |
Best estimate sent |
22 |
Emergency call with location retry |
Initial fail |
Retry successful |
23 |
Emergency call with SIP INVITE |
IMS signaling |
Call setup initiated |
24 |
Emergency call with SIP 183 |
Early media |
Ringback heard |
25 |
Emergency call with SIP 200 OK |
Call connected |
Voice path established |
26 |
Emergency call with SIP emergency URN |
Correct routing |
|
27 |
Emergency call with emergency APN |
Special bearer |
Prioritized traffic |
28 |
Emergency call with QoS bearer |
Dedicated bearer |
Low latency |
29 |
Emergency call with IMS emergency profile |
Special config |
Call allowed |
30 |
Emergency call with emergency fallback |
IMS not available |
CS fallback used |
31 |
Emergency call with SRVCC |
LTE to 3G |
Call continues |
32 |
Emergency call with VoLTE roaming |
Roaming network |
Call allowed |
33 |
Emergency call with no roaming agreement |
Emergency override |
Call allowed |
34 |
Emergency call with dual SIM |
Any SIM allowed |
Call connects |
35 |
Emergency call with eSIM |
Embedded SIM |
Call allowed |
36 |
Emergency call with test SIM |
Emergency profile |
Call connects |
37 |
Emergency call with test network |
Lab setup |
Call routed to test PSAP |
38 |
Emergency call with real network |
Field test |
Call connects to PSAP |
39 |
Emergency call with call recording |
PSAP records call |
Audio captured |
40 |
Emergency call with call transfer |
PSAP transfers call |
Seamless handover |
41 |
Emergency call with call hold |
PSAP holds call |
Call resumes |
42 |
Emergency call with call back |
PSAP calls back |
Call received |
43 |
Emergency call with silent call |
No voice |
Location still sent |
44 |
Emergency call with voice + data |
Location + voice |
Both transmitted |
45 |
Emergency call with crash sensor |
Airbag deployed |
eCall triggered |
46 |
Emergency call with vehicle telematics |
VIN, speed, direction |
Data sent to PSAP |
47 |
Emergency call with smartphone crash detection |
Fall detected |
Call initiated |
48 |
Emergency call with wearable device |
SOS button pressed |
Call initiated |
49 |
Emergency call with accessibility mode |
Voice disabled |
Text or location sent |
50 |
Emergency call with location confirmation |
PSAP receives coordinates |
Location verified |
IMS-Based Services - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
Initiate IMS video call |
VoLTE device to VoLTE device |
Video call connects |
2 |
Receive IMS video call |
Incoming call with video |
Video stream starts |
3 |
Switch voice to video mid-call |
Upgrade voice to video |
Video added successfully |
4 |
Switch video to voice mid-call |
Downgrade video to voice |
Video stops, voice continues |
5 |
Send RCS chat message |
IMS chat enabled |
Message delivered |
6 |
Receive RCS chat message |
IMS chat enabled |
Message received |
7 |
Send file via RCS |
Share image or document |
File sent successfully |
8 |
Receive file via RCS |
File transfer initiated |
File received |
9 |
Send location via RCS |
Share GPS location |
Location sent |
10 |
Receive location via RCS |
Incoming location share |
Map opens |
11 |
Group chat via RCS |
Multiple participants |
Messages delivered to all |
12 |
Group file sharing |
Send file to group |
File shared with all |
13 |
Group video call |
IMS group call setup |
Video call connects |
14 |
RCS presence update |
User status changes |
Status updated |
15 |
RCS typing indicator |
User typing |
Indicator shown |
16 |
RCS read receipts |
Message read |
Read status shown |
17 |
RCS delivery receipts |
Message delivered |
Delivery confirmed |
18 |
RCS message fallback |
Recipient offline |
Message sent as SMS |
19 |
RCS file size limit |
Send large file |
Warning or compression |
20 |
RCS file type support |
Send PDF, DOCX, JPG |
All supported |
21 |
RCS over LTE |
IMS session active |
Services available |
22 |
RCS over Wi-Fi |
IMS via ePDG |
Services available |
23 |
RCS over 5G NSA |
LTE used for IMS |
Services available |
24 |
RCS over 5G SA |
IMS over 5G core |
Services available |
25 |
RCS with dual SIM |
IMS active on one SIM |
Services available |
26 |
RCS with roaming |
Roaming IMS support |
Services available |
27 |
RCS with no data |
Mobile data off |
Services unavailable |
28 |
RCS with airplane mode |
LTE off |
Services unavailable |
29 |
RCS with IMS deregistration |
IMS down |
Services unavailable |
30 |
RCS with IMS re-registration |
IMS restored |
Services resume |
31 |
RCS with SIP OPTIONS |
Presence check |
Response received |
32 |
RCS with SIP MESSAGE |
Chat message sent |
Delivered |
33 |
RCS with SIP INVITE |
Video call setup |
Call connects |
34 |
RCS with SIP BYE |
End session |
Call ends |
35 |
RCS with SIP re-INVITE |
Modify session |
Update successful |
36 |
RCS with SIP NOTIFY |
Event notification |
Received |
37 |
RCS with SIP SUBSCRIBE |
Subscribe to presence |
Updates received |
38 |
RCS with NAT traversal |
Behind NAT |
Services work |
39 |
RCS with firewall |
IMS ports open |
Services work |
40 |
RCS with TLS |
Secure signaling |
Encrypted |
41 |
RCS with SRTP |
Secure media |
Encrypted |
42 |
RCS with QoS |
Prioritized traffic |
Low latency |
43 |
RCS with congestion |
Network load high |
Services adapt |
44 |
RCS with fallback to SMS |
IMS unavailable |
Message sent as SMS |
45 |
RCS with fallback to MMS |
File too large |
Sent as MMS |
46 |
RCS with contact discovery |
Sync contacts |
RCS users identified |
47 |
RCS with blocked contact |
Blocked user sends message |
Message blocked |
48 |
RCS with message history |
View past chats |
History available |
49 |
RCS with cloud backup |
Sync messages |
Backup successful |
50 |
RCS with test simulator |
Lab environment |
All services verified |
Roaming Support - Testcases
# |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
VoLTE call in home network |
No roaming |
Call connects |
2 |
VoLTE call in visited LTE network |
IMS interconnect available |
Call connects |
3 |
VoLTE call in visited LTE network |
No IMS interconnect |
Call fails or falls back |
4 |
VoLTE call with VoLTE roaming agreement |
Between operators |
Call connects |
5 |
VoLTE call with no roaming agreement |
No IMS support |
Call fails |
6 |
VoLTE call with IMS home routing |
IMS traffic routed to home |
Call connects |
7 |
VoLTE call with IMS local breakout |
IMS handled by visited network |
Call connects |
8 |
VoLTE call with SIP signaling |
SIP routed via IMS |
Call setup successful |
9 |
VoLTE call with RTP media |
Media path established |
Voice transmitted |
10 |
VoLTE call with QoS bearer |
Dedicated bearer in visited network |
Voice quality maintained |
11 |
VoLTE call with fallback to CS |
No VoLTE in visited network |
Call continues via 3G/2G |
12 |
VoLTE call with fallback to VoWiFi |
Wi-Fi available |
Call connects |
13 |
VoLTE call with dual IMS registration |
Home and visited IMS |
Call connects |
14 |
VoLTE call with single IMS registration |
Home IMS only |
Call connects |
15 |
VoLTE call with SIP OPTIONS ping |
IMS reachable |
Call setup proceeds |
16 |
VoLTE call with SIP 183 |
Early media supported |
Ringback heard |
17 |
VoLTE call with SIP 200 OK |
Final response |
Call connected |
18 |
VoLTE call with SIP re-INVITE |
Mid-call update |
Call continues |
19 |
VoLTE call with SIP BYE |
Call termination |
Call ends cleanly |
20 |
VoLTE call with IMS authentication |
AKA challenge |
Authenticated |
21 |
VoLTE call with roaming profile |
Correct APN and IMS settings |
Call connects |
22 |
VoLTE call with incorrect APN |
IMS not reachable |
Call fails |
23 |
VoLTE call with DNS resolution |
IMS domain resolved |
Call setup successful |
24 |
VoLTE call with NAT traversal |
Behind NAT in visited network |
Call connects |
25 |
VoLTE call with firewall in visited network |
IMS ports open |
Call connects |
26 |
VoLTE call with IPv6 roaming |
Dual-stack supported |
Call connects |
27 |
VoLTE call with IPv4 roaming |
Legacy IP supported |
Call connects |
28 |
VoLTE call with SIP over TLS |
Secure signaling |
Call encrypted |
29 |
VoLTE call with SRTP |
Secure media |
Voice encrypted |
30 |
VoLTE call with PCRF in home network |
Policy control applied |
QoS maintained |
31 |
VoLTE call with PCRF in visited network |
Local policy applied |
QoS maintained |
32 |
VoLTE call with IMS failover |
Backup IMS used |
Call connects |
33 |
VoLTE call with IMS deregistration |
Mid-call |
Call drops |
34 |
VoLTE call with IMS re-registration |
During roaming |
Call resumes |
35 |
VoLTE call with emergency call |
112/911 while roaming |
Call connects |
36 |
VoLTE call with eCall |
Vehicle crash abroad |
Call connects to local PSAP |
37 |
VoLTE call with call forwarding |
Forwarded to home number |
Call redirected |
38 |
VoLTE call with call barring |
Roaming restrictions |
Call blocked |
39 |
VoLTE call with call waiting |
Incoming call during roaming |
Call managed |
40 |
VoLTE call with call hold |
Hold and resume |
Call continues |
41 |
VoLTE call with call transfer |
Transfer to another number |
Call redirected |
42 |
VoLTE call with call recording |
Roaming call recorded |
Audio captured |
43 |
VoLTE call with billing record |
Roaming CDR generated |
Charges applied |
44 |
VoLTE call with IMS charging |
Roaming IMS charging applied |
Session tracked |
45 |
VoLTE call with network congestion |
Visited LTE congested |
Call quality adapts |
46 |
VoLTE call with high-speed mobility |
Roaming in transit |
Call continues |
47 |
VoLTE call with airplane mode toggle |
LTE re-enabled |
Call resumes |
48 |
VoLTE call with test SIM |
Roaming profile active |
Call connects |
49 |
VoLTE call with test network |
Lab roaming simulation |
Call verified |
50 |
VoLTE call with real network |
Field test abroad |
Call connects successfully |
Reference links