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.
- CSFB (CS Fallback) : This is the technology that switch the call to CS network (i.e, 2G or 3G network). This technology is used when UE does not support VoLTE (Voice over IMS) or LTE Network with VoLTE is not available. Amarisoft does not support this method since we don't support any 2G / 3G capability.
- VoLTE (Voice over LTE) : This is the technoligy based on IMS and SIP/RTP. This is the native (built-in) technology for Voice in LTE.
Table of Contents
- LTE VoLTE
NOTE : For a generic technical tips about VoLTE test, refer to this wiki.
Test setup for this tutorial is as shown below.
- SIM Card used in this tutorial is the one delivered with the system as it is.
- If you want to change the configuration, The tutorial Configuration Guide would help
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.
I also used the default configuration for mme (mme-ims.cfg) as shown below.
In this tutorial, I am using Anritsu Test USIM. Remember tel number since these will be used for SMS.
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.
I did following configuration on UE side.
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.
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)
Make it sure that UE IS assigned with IMS pdn.
Following is indicating that UE is registered to IMS server.
Make a call to 666 and check if the call gets established and hear loopback sound
Check the trace log in (ims) and you would see the call status as shown below.
Test 2 : MT Call from WebGui
You can make an MT Call from the WebGUI as follows :
Enable at least NAS, SIP, IMS in WebGUI log. Filter it out with NAS, SIP, IMS for convenience