How to make VoLTE calls more robust and less susceptible to packet delay and congestion?

[RFSpecialist]

First of all you have to find the routes RTP packts are lost and then discuss with transmission engineers to fix it.

Try to see RTP packets sent and not received in good RFfor both UE.

This is usually transmission network fault.

For this you have to activate u=plane pcap files E2E on both UEs.

Also check this topic: How LTE packets are prioritised in the backhaul media that in routers?