​​Test and Verification of VoLTE Service​

Objective

This document aims to assist customers to test and verify their IoT devices for VoLTE services provided by Telenor Connexion (TCXN).

1. Introduction

To secure voice in the ongoing 2G/3G sunset VoLTE is the natural replacement for legacy circuit switched (CS) voice. As compared to legacy 2G/4G services which used CS for voice, LTE is fully IP based and requires data services and IMS. Within IMS, calls are routed to, and handled by, the home operator´s IMS system. The device must be configured according to the home operator´s IMS systems settings.

Telenor Connexion follows the GSMA standard IMS settings (IR.92 - IMS Profile for Voice and SMS) to avoid complex device configurations. Our settings will be available through GSMA NSX (Network Settings Exchange) to all members/vendors. The vendors can then implement the settings in their products as preset or distribute as MBN (Modem Configuration Binary File.

It is required that the customers test and verify that the device works with Telenor Connexion IMS setup. Telenor Connexion can assist in what configuration needs to be set and how this is done in several well-known devices, however there are many different modules available, and their configurations may differ. Telenor Connexion is unable to provide support for all devices and so it is strongly recommended that vendor support be secured before commencing with VoLTE.

1.1 Prerequisites

1.2 Tested devices

TCXN has tested and verified our IMS platform with several major device vendors.

As our setup follows 3GPP standards, TCXN assumes that devices that also conform to 3GPP standards will function similarly - however the verification is still required.

Further, it is important to ensure your device follows the GSM Association TSG.34/TS.34 IoT Device Connection Efficiency Guidelines.

https://www.gsma.com/newsroom/wp-content/uploads//TS.34-v8.pdf

Especially 9.1

1.3 Device VoLTE Support

In order to use VoLTE, it is a requirement to ensure your devices supports VoLTE. Not all LTE devices support VoLTE, and some require firmware upgrade. Please consult your vendor if in doubt.

1.4 Coverage

To use VoLTE, LTE coverage is required.

In areas where there is no LTE coverage, CSFB may be used if present and supported by the device.

All emergency calls (112, 911) will be handled by the local MNO with CSFB (Circuit Switched Fall Back) or VoLTE Emergency if the radio network you are roaming in, supports it.

note

• As per GSMA VoLTE roaming recommendations, TCXN does not support SRVCC (Single Radio Voice Call Continuity). I.e., it is not possible to swap from VoLTE to CS during an ongoing call.
• VoLTE is not supported on NB-IoT
• VoLTE is supported by LTE-M, however most operators worldwide have not yet activated VoLTE on LTE-M.

1.5 Roaming

Most of the operators in the world support VoLTE. To be able to use VoLTE in a specific operator’s network with a TCXN SIM this operator needs to have a VoLTE roaming agreement with TCXN. Please contact your account manager to confirm availability in your deployment regions.

1.6 SIM & Subscription

TCXN VoLTE require a SIM-card in the 240 42 IMSI range (International Mobile Subscriber Identity).

The VoLTE service needs to be ordered and enabled on your TCXN subscription.

2. Device configuration

2.1 General setup

VoLTE configuration differs from vendor to vendor and even between models from the same vendor. TCXN cannot provide proper commands or configurations for all devices. Please refer to your device vendors support or manual.

We strongly recommend you test VoLTE from a factory reset device and start with verifying the VoLTE service alone before adding other settings. This is to rule out non-VoLTE-related issues while verifying.

2.2 Device configuration summary

• Set default APN (Access Point Name) to internet.cxn, connect.cxn or the one you are using for data.
• Enable IMS/VoLTE
• Add secondary APN called “ims”
• Want 2G/3G CS calls as backup for VoLTE calls?
  • Set the device to be voice centric.
• Are you only using VoLTE and Data on 4G?
  • Set the device to data centric.
• Want to use SMS with VoLTE enabled device?
  • Configure the device to use SMS over NAS/SGs/CS.

2.3 APN

The VoLTE service makes use of the default APN data bearer (for instance internet.cxn), together with a secondary APN named “IMS”. When enabling IMS or VoLTE in the device, many devices add the IMS APN automatically. If you can't see it defined after enabling IMS, please add it manually.

note

IMS APN alone will not work even if you are not going to use any other services. You need to have a primary APN for data

2.4 Voice vs data centric

When a device attaches to the network it will indicate as 'voice centric' or 'data centric'.

To be able to use 2G/3G for calls as backup for VoLTE, your device should be configured as voice centric. The device must, of course, also be allowed to connect to 2G/3G network as well as 4G/LTE.

If your device is configured as ‘data centric’, you will be able to use VoLTE and data, but not 2G and 3G. When the device is out of 4G coverage, it will try to change operator to find another network supporting 4G with VoLTE.

2.5 Messaging, SMS

Currently TCXN supports SMS over SGs. SGs is an intermittent solution which uses CS core services to transfer SMS between CS & PS. Even without 2G and 3G radio coverage.

When enabling IMS, most devices also try to send SMS over IMS. While some then automatically try other methods, most refuse to send the SMS.

If you´re unable to send/receive SMS while IMS is enabled, you need to configure the device to send with SMSoNAS (SGs & SGd). Please refer to your device vendor for how this is done.

2.6 DTMF (Dual Tone Multiple Frequency)

DTMF is supported via VoLTE as well. This might need to be set up in your device, depending on whether you want to receive or send DTMF. Refer to your device manual for commands.

3. Verification

Before you roll out VoLTE to all your devices, we need you to complete verification test cases. The TCXN basic test cases document (download here) will help you verify the VoLTE service. If you have use/test cases which are not covered, feel free to add them to the document.

1. Reach out to your TCXN customer contact to order and enable VoLTE for the test.
2. Download the test sheet
3. When you have finished the tests, return the test sheet to technical support. We need your tests and logs to be no more than seven (7) days old. Older logs do not contain the level of details needed for us to verify network logs.
4. TCXN will get back to you with results and to fully enable VoLTE on desired sims.

4. Support & Troubleshooting

For support & troubleshooting please contact our Service Operation Center (SOC).

Send an email to technicalsupport@telenorconnexion.com with as much detail about your problem as possible. How the problem occurs, error message, timestamps, device logs, location etc. Important that you write VoLTE device testing in subject of email.

Bear in mind that for us to check the network logs, we need your tests and logs to be no more than seven (7) days old. Older logs do not contain the level of details needed for us to verify network logs.

5. Glossary of Terms

CS	Circuit Switched
PS	Packet Switched
IMS	IP Multimedia Subsystem
VoLTE	Voice over LTE
SMS over NAS	SMS over the Non-Access Stratum Procedures
SGs	an optional interface between a 2G (GERAN) / 3G (UTRAN) MSC and an LTE/EPC MME
SGd	an optional interface enables the transfer of short messages between the MME and the SMSC using Diameter protocol