This tutorial shows how to do VoLTE Loopback test with a commercial UE on Amari Callbox. VoLTE loopback means UE initiate VoLTE call and Callbox accept the call and loopback the SIP/RTP back to UE. There is no independent receiving UE. If you are using USIM card from Amarisoft, you don't need to change anything in default LTE configuration. You just need to do some settings on UE side.

There are two main technology to implement Voice in LTE as below.

NOTE : Since Amarisoft Callbox VoLTE is based on Loopback mechanism, most of the connected property (e.g, type of Voice Codec) is determined by UE capability, not determined by Callbox feature.



Table of Contents



NOTE : For a generic technical tips about VoLTE test, refer to this wiki.




Test Setup


Test setup for this tutorial is as shown below.  

TestSetup Callbox UE 1sdr 01




Key Configuration Parameters


Followings are important configuration parameters for this tutorial. You may click on the items for the descriptions from Amarisoft documents.






I used the enb.default.cfg (LTE default configuration) as it is without changing any contents in it.

LTE SG SMS Config 01

I also used the default configuration for mme (mme-ims.cfg)  as shown below.

LTE SG SMS Config 03

In mme-ims.cfg file, you would notice that ue_db-ims.cfg is used as ue db.

LTE SG SMS Config 04

In this tutorial, I am using Anritsu Test USIM. Remember tel number since these will be used for SMS.

LTE SG SMS Config 05

Following setting is for VoLTE loopback configured in ims.default.cfg. If you make a call to this number from the phone, the Callbox will do VoLTE loopback.

LTE VoLTE Loopback Config 05


I did following configuration on UE side.

LTE VoLTE Loopback Config 06



Perform the test


Test 1 : VoLTE Loopback


Start LTE service and check basic cell configuration. Any cell configuration is OK as long as it is LTE cell.

LTE VoLTE Loopback Run 01

Power On UE and make it sure that UE get registerred. (NOTE : If UE is in idle mode, you would not see anything listed here. Then just proceed to next step)

LTE VoLTE Loopback Run 02

Make it sure that UE IS assigned with IMS pdn.

LTE VoLTE Loopback Run 03

Following is indicating that UE is registered to IMS server.

LTE VoLTE Loopback Run 04


Make a call to 666 and check if the call gets established and hear loopback sound

LTE VoLTE Loopback Run 05


Check the trace log in (ims) and you would see the call status as shown below.

LTE VoLTE Loopback Run 06



Test 2 : MT Call from WebGui


You can make an MT Call from the WebGUI as follows :

LTE VoLTE Loopback Run Test2 01

LTE VoLTE Loopback Run Test2 02

LTE VoLTE Loopback Run Test2 03




Log Analysis


Sample Log


Enable at least NAS, SIP, IMS in WebGUI log. Filter it out with NAS, SIP, IMS for convenience

LTE VoLTE Loopback Log 01


LTE VoLTE Loopback Log 02