The Little Known Problems with VoLTE Emergency Calling
How to Test for 4G Emergency Calling Support on Android
Table of Contents
- How to Test for 4G Emergency Calling Support (Very Advanced)
- Emergency Calling Examples (Screen Recordings) - How to Test for 4G Emergency Calling Support (Extremely Advanced)
- How to Fix a device that cannot make 4G Emergency Calls
- VoLTE Emergency Calling & Roaming - Device Modem Configurations & Emergency Calling
- Further Information & Resources
- Sources & References
UPDATE/WARNING:
As of 28 October 2024, Australian Telcos are now blocking Device IMEI TAC Codes. So Your perfectly compatible device may be entirely blocked from all services including Data & SMS. The Telcos are even blocking devices that are on their official support lists! If the phone was sold through another carrier or retail it may be blocked. This is even true for locally sold Models!
If your device currently doesn’t have Working 4G Data with any sim card you won’t be able to fully test for VoLTE on your device, though limited testing for VoLTE Emergency Calls is still possible with no sim card.Blocked 4G devices that are capable of VoLTE Emergency Calling are still able to ‘Camp-on’ to networks to place Emergency Calls, however it’s a coin flip which network and band you will get. Devices that rely on 2G or 3G for Emergency Calling will just get stuck on ‘calling’.
Learn more below!
IMPORTANT UPDATE 09/2024: Based on recent changes to Australia’s ‘Emergency Call Service Determination’ from 1 November 2024 any handsets the carriers believe can’t call 000 (112) will be blocked from connecting!
This will impact devices that have been manually updated to work for VoLTE Calling and Emergency Calling as they aren’t ‘officially’ supported.“Subsection 6(2) directs ACMA to include requirements for providers to identify mobile phones unable to access Triple Zero, notify the user, provide assistance if necessary to access an alternative mobile phone, and cease providing service to the affected device. Providers will also be required to not provide service to a prospective customer seeking service with an affected mobile phone. This requirement makes clear the responsibility providers have to ensure mobile networks provide access to the emergency call service.” [..] “The amendments to the Determination to be made under section 6(2) are to be determined and commence in full by 1 November 2024.”
Australian Communications and Media Authority (Emergency Call Service Determination) Direction 2024 — Explanatory Statement https://www.legislation.gov.au/F2024L01103/asmade/text/explanatory-statement
More read more below (including Petition Link)!
4G Emergency Calling Testing
A device may support VoLTE Calling (IMS Registration) on a network but may not be able to successfully make calls to emergency numbers. The below instructions will allow you to test for 4G Emergency Calling support on most (Qualcomm Based) Android devices. (Android 8.0 & 9 Tested)
Note: Checking the ‘IMS Status’ in the Radio Info (4636) interface is not sufficient to check for Emergency Calling support.
Guide: How to Check for Working 4G VoLTE Calling on Android Handsets
Disclaimer: Testing is to be done at your own risk and refer to the relevant laws of your country before following these steps. Do Not make calls to Emergency Numbers unless you have a genuine emergency. The following information has no guarantees or warranties regarding the accuracy of the testing and is for educational purposes only. Emergency Calling networks and systems vary depending on country, available networks and devices settings. These instructions do not constitute an endorsement to perform these steps. This information has been provided solely in the interests of public safety & education.
How to Test for 4G Emergency Calling Support (Very Advanced)
Step 1: Download & Install the App “NetMonster” from the Play Store https://play.google.com/store/apps/details?id=cz.mroczis.netmonster
Step 2: Remove the Sim Card from your device.
This is to ensure the device can place anonymous emergency calls over 4G and ‘camp-on’ (‘roam’) to alternative networks.
Removing the sim also prevents a call back to your phone number as the caller id will be ‘anonymous’. You may also wish to temporarily disable ELS (Emergency Location Service) in the System Location Settings.
Note: On some devices removing the Sim Card will revert the device modem configuration to a Non-VoLTE enabled config.
Some devices may only load a ‘VoLTE Calling & 4G Emergency Calling’ enabled modem configuration when a ‘supported’ carrier network sim card is inserted.An unactivated ‘prepaid’ network sim card could be used to test for emergency calling support on these devices, however the device may still be unable to make anonymous emergency calls over 4G with no-sim and on every network.
Some Telstra and Vodafone/Lebara $2 sim cards will register VoLTE without an activated service.* $2 sim cards can be used to test Emergency Calling on each network.
(*As of Q3 2024)See here and below to learn more about the modem configurations on devices.
Step 3: After Sim Removal/Device Restart Open ‘NetMonster’.
NetMonster will display a Network Band icon in the notification area.
(e.g ‘700’ for 700Mhz LTE Band 28).
If you don’t see a number you may need to change the ‘Notification Icon’ option in the app settings to ‘Band’. Note: Some devices may only display ‘3G’ or ‘4G’.
Step 4: Once NetMonster has been opened go to the three dots in the bottom corner [ ⋮ ] and select ‘Phone Info’.
This will launch the *#*#4636#*#* ‘Phone Info’ Debug as shown in this guide ‘Method 2: IMS Status Check’.
Step 5: Under ‘Set preferred network type’ Change from the default [e.g LTE/UMTS auto (PRL)] to ‘LTE Only’. (Remember to note the original value & restore after testing, a restart may be required)
By changing this to ‘LTE Only’ it will force the phone to try and connect to a 4G network first for Emergency Calling.
By default a device that can make Emergency Calls over 4G with VoLTE may default to 2G or 3G (if available) depending on signal strength and other factors.
It’s important to note that a device may say “Emergency Calls Only” within the ‘Phone Info’ Screen or notifications area but that does not mean the device can actually make an Emergency call over 4G/LTE.
Note: On some Samsung (Exynos) phones (& other devices), setting ‘preferred network type’ does not work properly if there is no sim card inserted. An old or inactive sim card could be used to test 911/000/112 calls with a sim inserted.
You may also need another App such as ‘Force LTE Only (4G/5G)’ to set the device to ‘LTE only’ on some newer devices (e.g. Phones on Android 11+). Some devices may also require a sim card to be inserted first.
Step 6: After changing to ‘LTE Only’ pay close attention to the NetMonster Band Icon in the notification bar and note it down. (e.g 700 etc)
When a device has no sim card inserted you lose the 3G/4G(LTE) network icon.
NetMonster provides its own ‘band icon’ which allows you to see if the network connection (frequency/band) changes during a call.
For Australia this means it’s connected to either the Telstra or Optus 4G VoLTE Network (both use 700Mhz B28 as their primary 4G Band).
Vodafone primarily uses the 850Mhz 4G Band (5) and other 4G Bands may display depending on the capabilities of the device and available networks. Devices without 700Mhz LTE support may encounter issues placing emergency calls in regional areas with only 700Mhz Telstra coverage.
Carrier Frequency Bands can be found at https://frequencycheck.com/carriers
Note: If NetMonster doesn’t show an LTE band icon after setting the (4G) Device to ‘LTE Only’ then you may need to use another ‘Force LTE’ app or an inactive sim card (as shown above) to set the device to ‘LTE Only’.
Do not proceed until NetMonster shows you are connected to a 4G Band.
Step 7: Performing a Test Call
(Disclaimer: Proceed at your own risk, these steps are for educational purposes only.)
In order to test for working 4G Emergency Calling a test call to a genuine emergency number is required. The phone will then try to attach to the 4G network via an ‘SOS’ APN which is configured in the device firmware.
Devices can be configured for 4G Emergency Calling but can fail to properly attach to the network when making a call. This will be represented by the call getting stuck or switching/falling back to 3G after a delay.
A device set to ‘LTE Only’ that can make Emergency Calls over 4G should connect immediately after dialling. Devices that fall back to 2G/3G will have a noticeable delay before the call timer starts counting. Once the call timer starts counting up you can immediately hang up, the call does not need to be longer than 1–2 seconds. In Australia the first thing you will hear is a short pre-recorded message, after the message the call is then directed to a call centre.
Note: This step requires users to pay close attention to the NetMonster icon and watch to see if it changes to a 3G Band Frequency (850Mhz, 900Mhz etc) when placing the call. Be aware that 850Mhz can be either 3G or 4G. Vodafone AU uses the 850Mhz 4G Band and Telstra uses the 850Mhz 3G Band. Optus 3G uses the 900Mhz Band. (Current as of Q2 2024)
In the dialer dial 112 (or the emergency services number for your country) and Press Call, watch the NetMonster Band icon and see if it changes.
After 1–2 Secs of a connected call hang-up!
In one of the below examples you can see NetMonster displays ‘1800Mhz’ which is an Australian 4G/LTE Band. In some instances and on some devices it will display 700(Mhz) instead (B28).
The icon will depend on the device firmware and radio capabilities of the device. The below examples indicate when a device has working 4G Emergency Calling.
(With root can you definitively confirm with Network Signal Guru — See below).
If a 4G Band (e.g. 700, 1800) changes to 900 or 850* after a short delay/pause, that indicates the device cannot make Emergency Calls over 4G and relies on 2G or 3G (CFSB).
Emergency Calling Examples (Screen Recordings)
Below are some screen recorded examples of Failed and Successful emergency calls over 4G.
Pay close attention to the NetMonster Band icon in the notification bar.
Description: In the above example the device fails to place an Emergency Call over 4G even though ‘VoLTE’ is active and available. The device falls-back to another carrier’s 3G Network (if present).
The device in use (Xperia X — SD 650) was running a Vodafone AU (vha) Modem Configuration, that configuration does not have working 4G Emergency Calling with or without an active sim card.
The device in the above example was using an unactivated Vodafone Sim Card. VoLTE calling was working to Vodafone ‘Voicemail’ and ‘Recharge’ phone numbers.
Description: In the above example the device fails to place an Emergency Call over 4G and the call does not fall-back to 3G!
The device (XZ1/C SD 835 SoC) was running an O2 UK Modem Configuration, the device will attempt to make an Emergency Call over 4G but fail to attach correctly and establish an IMS & VoIP/SIP connection. The device will stay stuck on ‘Calling’ until the user hangs up the call.
This type of compatibility issue was pointed out at the 2022 EENA Conference and is a well known issue in the industry, though minimal progress has been made to fix the problem.
This is also the failure scenario for a 4G device that requires 2G or 3G for Emergency Calls when there are no 2G/3G Networks available. The device will just get stuck on “Calling”, and the call will never connect.
Normal 4G Emergency Calling Behaviour (With Active Sim & VoLTE)
Description: In the above example the device successfully places an Emergency Call over 4G with an active ‘VoLTE’ service. This is the intended Calling behaviour for a device that supports 4G Emergency Calls.
The device in the above example was using an unactivated ‘prepaid’ Vodafone Sim Card. VoLTE calling was working to Vodafone ‘Voicemail’ and ‘Recharge’ phone numbers.
The device (Android 9 — Xperia XZ1C— SD 835) was running a GSMA (‘Open Market’) IR.92 + IR.51 VoLTE Modem Configuration. That configuration has both working 4G VoLTE Calling on Vodafone AU & Emergency Calling (as shown above), in addition to supporting WiFi Calling. (See here for more info)
Note: This modem configuration was manually loaded on the device using a ‘temp-root’ (bindershell) method.
However, as Vodafone did not sell this model of device and it was not sold in Australia they do not recognise that it supports both VoLTE Calling and Emergency Calling on Australian Networks!
How to Test for 4G Emergency Calling Support (Extremely Advanced)
An alternative or supplementary method for testing Emergency calls is via the Application ‘Network Signal Guru’. NSG is best used with Root access to the Firmware, however NSG can still provide some more detailed network Band information and history in non-root mode.
To test with NSG, launch the app (with root) prior to making a call and ensure the device is set to ‘LTE Only’ within the 4636 ‘Phone Info’ Interface. Make a brief call to 000/112 and hang up, then check the Signalling Log in NSG for IMS Registrations like the below example.
How to Fix a device that cannot make 4G Emergency Calls
If you have a device that can make calls over 4G but not to Emergency Numbers you will likely need to change the Modem Configuration that is on the device to enable calling. This will likely require root or temp root to the device (or alternative device firmware).
There are tools like QPST and EFS Tools that can be used to flash a different modem configuration onto the device.
For example on the Sony Xperia X the Vodafone AU modem config (vha_ims) does have working VoLTE calling on Vodafone (& Optus) but it does not have working Emergency Calls.
To resolve this issue for the Xperia X (and other devices) the loaded modem configuration needs to be changed out to one that can both support Emergency Calling over 4G and VoLTE with the network. Not all configurations will support both.
Fortunately devices running the generic GSMA IR.92 ‘Open Market’ Configuration work with the Vodafone Network. The ‘ir92 gte’ modem configs available on the Xperia X (X Performance, XZ1 etc) support both VoLTE Calling on Vodafone and 4G Emergency Calling.
If your network does not support a generic ‘Open Market Device’ Configuration and the telco native configuration doesn’t have working 4G Emergency Calling then it may not be possible to entirely fix without handset and chipset vendor support.* (TBC). With some devices it is possible to load the MBN files for a different generation of Qualcomm SoC and enable VoLTE.
For more information for which Qualcomm modem configs are likely to support 4G Emergency Calling (& ‘Open Market’) see the testing spreadsheet and additional resources below.
VoLTE Emergency Calling & Roaming
In March 2024 prior to the Switch-off of 3G Networks in Australia, the Federal Government announced that more than 740,000 4G VoLTE enabled phones would no longer be able to call Emergency Services after the 3G Networks were switched off.
In early April 2024 this number was increased to more than 1 million devices. Telstra was set to switch off their 3G Network on 30 June 2024. Telstra extended their switch off to 31 August in May 2024.
On 14 August 2024, Telstra and Optus further extended the 3G switch off date to 28 October 2024.
Vodafone AU (TPG Telecom) switched-off their 3G Network starting in December 2023, this was concluded in late January 2024.
As a result of the switch-off inbound Roaming customers have been receiving text messages advising they will no longer have access to voice, text or data and emergency calling whilst roaming in Australia.
Even customers with 5G iPhones have received such text messages.
An example is below.
Devices without VoLTE Roaming cannot make VoLTE calls when roaming on another 4G network. VoLTE Roaming uses the S8HR Architecture, this architecture routes the calls to the home mobile network.
Roaming devices that lack VoLTE Roaming support can use 2G or 3G Networks (if available) for making and receiving calls (via Circuit Switched Fallback). In countries without either 2G or 3G Networks, Roaming devices will not have access to call service from the connected Roaming Network.
Further to that, Optus (an AU telco) says VoLTE and VoLTE (International) Roaming should work on all Samsung Phones with Android 12 and above.
https://www.optus.com.au/mobile/plans/international-roaming/volte
Android 12 was only released in late 2021 so people who have Android phones older than 2020/2021 are likely to encounter issues with either switching providers or when roaming overseas.
Devices from Android 4 to 11 make up 69% of the Android Device Market as of April 2023.
Devices without VoLTE Roaming support may encounter issues placing Emergency Calls when Roaming on 4G.
Device Modem Configurations & Emergency Calling
Not all devices that have been sold as ‘VoLTE capable’ support making calls to Emergency Numbers over 4G/LTE with VoLTE. Some carriers and manufacturers have disabled the ability for phones to call Emergency Services with VoLTE and the devices are reliant on 2G or 3G Networks to make calls to Emergency Services.
Many carrier modem configurations may be configured for VoLTE Calling but not for Emergency Services.
In 2022 at the European Emergency Number Association (EENA) Conference Telecoms Expert Rudolf van der Berg made a presentation to the Conference outlining serious compatibility issues with VoLTE Calling and Emergency Calling.
One of the major issues he raised is that many 4G/LTE Phones (both European & International) are completely unable to call (911/112) Emergency services without the presence of 2G/3G (Circuit Switched Calling) Networks.
As an example, see below tables of Qualcomm Modem configurations that were tested on Australian Networks. (Telstra, Optus and Vodafone AU, in addition to 000 ‘Triple Zero’ (112) 4G Emergency Calls)
As noted in the 2022 EENA Presentation in many countries phones have been specifically configured via software/firmware to block access to Emergency Services over 4G and entirely rely on 2G/3G.
As shown in the above tables there are major inconsistencies when making VoLTE calls between various networks. Only about ~33% of the various tested network configurations support emergency calling over 4G.
It’s also worth noting that devices running the Singtel Modem Configuration Do Not work on the Optus network despite Singtel being the parent company, 4G Emergency calls also do not work with the tested Singtel Modem Configurations.
Devices running the generic IR.92 ‘Open Market Device’ configuration can work on competing Australian networks Optus & Vodafone/TPG including for Emergency Calls on all AU networks.
Note: ‘Open Market’ config devices can still typically call 000/112 on Telstra as Emergency Calling is a separate bearer/connection compared to standard phone calls (IMS vs SOS APN/Bearer).
For reference, the Snapdragon 820 Chipset (2016) was used in some of the following devices:
- Samsung Galaxy S7 & S7 Edge (USA)
- Sony Xperia XZ
- OnePlus 3
- LG G5
- Google Pixel 1 (Snapdragon 821)
- HTC 10
- HTC U Ultra (Snapdragon 821)
GSM Arena — Phone Finder — Snapdragon 820 + 821 Devices https://www.gsmarena.com/results.php3?sChipset=2,3
The Snapdragon 835 Chipset (2017) was used in some of the following devices:
- Samsung Galaxy S8 (USA & China)
- Samsung Galaxy Note 8 (USA & China)
- Sony Xperia XZ Premium
- Sony Xperia XZ1 & XZ1 Compact
- OnePlus 5 & 5T
- LG V30
- Google Pixel 2
- HTC U11 & U11+
GSMArena — Phone Finder — Snapdragon 835 Devices
https://www.gsmarena.com/results.php3?sChipset=1
Note: The test results noted with ‘NO — Call Fails’ are devices that support 4G Emergency calling in their respective home market or network, but Emergency Calls fail to connect on Australian 4G Networks even when 3G is available!
Further Information & Resources
VoLTE Device Testing Information — Original Write-up — Nov 2023
Google Doc — ‘2G/3G Switch-Off & 4G VoLTE Calling Device Information’
4G Emergency Calling Testing Information — Original Write-up — Jul 2024
Google Doc — ‘2G/3G Switch-Off & 4G VoLTE Calling Device Information — Emergency Calling Testing’
Senate Inquiry — Shutdown of the 3G mobile network — Submission 32 — James Parker
https://drive.google.com/file/d/1wrwLDogtUCUn70GWY8yCsqbZvzZEvj2q/view?usp=sharing
Senate Inquiry — Shutdown of the 3G mobile network — Supplementary Submission 32 — James Parker
https://drive.google.com/file/d/1SNsWzH5rOWl62Wxe0I0dQbyDMvLQQcPm/view?usp=sharing
Sources & References
What is a Circuit Switched Fallback (CSFB)?
https://ribboncommunications.com/company/get-help/glossary/csfb
Siretta — Circuit Switched vs Packet Switched Networks
https://web.archive.org/web/20231206141205/https://media.digikey.com/resources/siretta/siretta-circuit-switched-vs-packet-switched-networks.pdf
Doug Makishima, GSMA — ITU Workshop on “Voice and Video over LTE”
https://www.itu.int/en/ITU-T/Workshops-and-Seminars/conformity-interoperability/20150112/Documents/Abstracts%20and%20Presentations/S3P5_Doug_Makishima.pdf
GSMA New VoLTE Specification to remove Market Fragmentation (07/2016):
https://www.gsma.com/futurenetworks/digest/new-gsma-volte-specification-removes-market-fragmentation/
Annoyed that your phone won’t work on VoLTE or VoWIFI on other carriers? GSMA is working it:
https://ausdroid.net/news/2017/11/18/annoyed-phone-wont-work-volte-vowifi-carriers-gsma-theyre-working-answer/
GCF GSMA IR92 VoLTE Spec Presentation: https://www.globalcertificationforum.org/static/uploaded/c1683a68-b94c-4c75-a6470136dfed73a9.pdf
OptimERA- ‘VoLTE Emergency Calls — Testing of 3GPPCompliance in OEM Handsets’ — January 2020
https://optimerainc.com/wp-content/uploads/2021/11/OptimERA_VoLTE_Emergency_Calls_Report.pdf
EENA — Ensuring continuity of access to emergency services/VoLTE Standardisation Problem
https://eena.org/blog/webinars/volte-standardisation-problem/
The Potential Perils of 2G and 3G Switch Offs
https://eena.org/knowledge-hub/press-releases/the-potential-perils-of-2g-and-3g-switch-offs/
‘Should we stop the shutdown of 2G/3G to save lives??’ Rudolf van der Berg — Stratix — EENA 2022
https://drive.google.com/file/d/1WC16k8C1gpeFRJif23yDIuLSRg1OJOnZ/view
Operators expect ‘blood on the highway’ as US visitors lose 911 Access
https://www.capacitymedia.com/article/2a8jhlzsoucvynqade3up/news/operators-expect-blood-on-the-highway-as-us-visitors-lose-9-1-1-emergency-access
Additional Test Cases for IMS Emergency Calling — Wayne Cutler, GSMA
https://www.itu.int/cities/wp-content/uploads/2023/06/3_Wayne-Cuttler.pdf
Ofcom — ‘3G and 2G switch-off — Our expectations of mobile providers’ — 02/23 https://www.ofcom.org.uk/__data/assets/pdf_file/0025/252592/3G-and-2G-switch-off.pdf
Comms Alliance - Industry Guidance Triple Zero Test Call Procedures
https://www.commsalliance.com.au/Publications/all/Industry-Guidance-Notes/industry-guidance-note-ign020-ECS-Requirements-Triple-Zero-Test-Call-Procedures
Australia’s 3G Switch-Off — 2024
3G Switch-Off Could Stop Triple-Zero Calls | 10 News First — 17 March 2024
https://www.youtube.com/watch?v=iK98wI6d-W0
ABC — ‘Millions of Devices Caught out by 3G Shutdown’ — Jane Norman — 8 April 2024
https://www.abc.net.au/news/2024-04-08/million-iphone-android-devices-caught-out-3g-shutdown/103673864
ABC — ‘Telstra to Extend 3G Shutdown’ — Jane Norman — 6 May 2024
https://www.abc.net.au/news/2024-05-06/telstra-to-extend-3g-network-shutdown/103808110
Senate Estimates 30 May 2024 Video Stream — Department of Infrastructure
https://www.aph.gov.au/News_and_Events/Watch_Read_Listen/ParlView/video/2488638?startTime=04480 (Start 10:04)
https://www.aph.gov.au/News_and_Events/Watch_Read_Listen/ParlView/video/2488638?startTime=08118 (Start 11:05)
Shutdown of the 3G mobile network — Australian Parliament Senate Inquiry
https://www.aph.gov.au/Parliamentary_Business/Committees/Senate/Rural_and_Regional_Affairs_and_Transport/3GNetworkShutdown
Senate Inquiry — Shutdown of the 3G mobile network — Submission 32 — James Parker
https://drive.google.com/file/d/1wrwLDogtUCUn70GWY8yCsqbZvzZEvj2q/view?usp=sharing
Senate Inquiry — Shutdown of the 3G mobile network — Supplementary Submission 32 — James Parker
https://drive.google.com/file/d/1SNsWzH5rOWl62Wxe0I0dQbyDMvLQQcPm/view?usp=sharing
Rural & Regional Affairs & Transport — 3G Shutdown Senate Inquiry — 23/07/2024 — Public Hearing
https://www.youtube.com/live/Tlofv0UfoI0?t=7833s
Rural & Regional Affairs & Transport — 3G Shutdown Senate Inquiry — 24/07/2024 — Public Hearing
https://www.youtube.com/live/HvDvnfWTou0?t=355s
Rural and Regional Affairs and Transport References Committee — 23/07/2024 — Shutdown of the 3G mobile network — Hansard
https://www.aph.gov.au/Parliamentary_Business/Hansard/Hansard_Display?bid=committees/commsen/28167/&sid=0004
Quarterly reports from Telstra & Optus regarding 3G switch offs from 27 Mar 2023 to 27 Mar 2024
https://www.infrastructure.gov.au/sites/default/files/documents/foi-24-352--documents-for-release--pdf.pdf
https://www.infrastructure.gov.au/about-us/freedom-information/freedom-information-disclosure-log
Correspondence to, and responses from, the Minister for Communications relating to the shutdown of 3G networks between 27 March 2023 and 27 March 2024
https://www.infrastructure.gov.au/sites/default/files/documents/foi-24-354--documents-for-release--pdf.pdf
