July 13, 2021

Single sided calls in the VoLTE core

When your VoLTE subscriber places a call and doesn’t hear the other party, his next call will be to complain. This week we helped one of our tier-1 mobile SP to troubleshoot a series of single sided calls in a matter of minutes avoiding further escalations. Read below how:


One of our large mobile service providers replaced legacy 4G core with a new Mavenir virtual VoLTE core. While migrating subscribers there was large increase of end customer complaints about single-sided and silent calls.

Luckily, the SP was able to detect the root cause in matter of minutes using Voipfuture Qrystal.

In the below, the B-party was not able to hear the A-party. The reason is that the RTP flow from A-Party to B-Party is missing between the P-CSCF and the VoWifi UE. The RTP flow was present in the IMS network between the MGW and the P-CSCF, but was stopped in the new virtual VoLTE core. This troubleshooting is possible when the RTP Media on the VoLTE core is monitored on the access and IMS side.