Devices Set up & Troubleshooting

IMS service troubleshooting

What is IMS?

IMS stands for IP Multimedia Subsystem. It is a component of the core network which permits the latest voice calling technology. In essence, it allows voice calls to be carried using data (such as 4G or 5G), which means that coverage can be extended and call quality can be greatly improved compared to traditional voice calls (CSD or Circuit-Switched Data).

What does IMS do?

IMS allows users to access the latest voice services, including:
·        VoLTE: the ability to make calls using the 4G (or LTE) network
·        VoWiFi: the ability to make calls using your home, office or public Wi-Fi, which is especially useful if there is no coverage for cellular data

They also carry benefits such as:
·        Being able to talk and surf on 4G at the same time
·        Faster call connection
·        Greater call quality
·        Extended coverage from the 4G network
·        Access to the 800MhZ spectrum which is reserved for VoLTE usage

What do I need to access VoIMS services?

To enable VoIMS for a user, the requirements are:
·        The “VoIMS service (VoLTE & VoWiFi)” is provisioned to ”on” via Auriga or API
·        The user must have an IMS, VoLTE or VoWiFi compatible handset
·        Handset settings must have IMS, 4G (or LTE) calling and Wi-Fi calling set to “on” (the naming and options may vary according to the handset and manufacturer)
·        Handset settings must have 4G data set to on
·        The 2G/3G/4G or 2G/3G/4G/5G service is provisioned to ”on” via Auriga or API
·        The user must be in within 4G coverage, or in a Wi-Fi zone and connected to the Wi-Fi network

Enable Wi-Fi calling on an Apple device: https://support.apple.com/en-gb/HT203032
For android or other devices, check your manual.

What if I can’t access VoIMS services?

The above criteria must be fulfilled to access the services.
Once the VoIMS service is provisioned, and the handset settings enabled, it is recommended to restart the handset to reattach to the network and to attach to the services that have recently been enabled.

If VoWiFi is not working, go outside or to a zone with 4G coverage, disconnect Wi-Fi and test a call using VoLTE. If the calls go through correctly, there may be a problem with the Wi-Fi Router or its internet permissions (which must be resolved with your Wi-Fi provider).

What happens if I can’t get 4G signal?

When 4G is not available, your device will automatically pass calls through the 2G or 3G networks if you are within coverage.

Be aware that the benefits of VoLTE will be lost in this case (surf and talk, voice quality…).

What happens if VoIMS suddenly stops working?

Try following the following steps:
·        Check that your handset is connected to 4G, with a good signal
·        Turn off power saving mode: sometimes this mode stops background processes such as VoWiFi
·        Check the settings on the handset have not been reset or disabled (such as by accident or a software update)
·        Turn on aeroplane mode, wait a few seconds, and turn it back off again
·        Restart the handset
·        Reset network settings

Reset network settings on an Apple device: https://support.apple.com/en-gb/guide/iphone/iphea1c2fe48/ios
For android devices, check your manual.

Do IMS services work in roaming?

VoLTE and VoWiFi are currently not supported outside of the UK.

What about 5G?

When you are making a call, your phone will automatically switch to a 4G network.
This means you will not be able to use 5G whilst on a call, but you’ll nonetheless benefit from the speeds of 4G .

Surfing on 5G whilst on a call will become possible with the launch of VoNR (Voice over New Radio / also referred to as Voice over 5G or Vo5G). VoNR is likely to become standardised in the market some time after the standardisation of 5G SA (stand alone).

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