At the high level, Application Server (AS) and Media Resource Function (MRF) both the nodes are involved in IMS based conference call. Application Server keeps SIP service logic while Media Resource Function mainly involve in audio/video codec. For example: IMS based conference call uses Application Server and Media Resource Function.
I went through the details covered in following link but not found anything about HSS. http://tech.queryhome.com/60183/what-the-role-ims-in-lte-technology-provide-the-voice-service
Sometimes due to coverage hole issue in the LTE network, the ongoing VoLTE is continued to UE by using the CS network like GSM network. This is known as SRVCC (Single Radio Voice Call continuity). What messages are exchanged between network nodes when UE moves from LTE to GSM ?
There are two scenarios of VoLTE call. 1. Originator and Receiver both are connected in LTE network. 2. Either one of them is not in the LTE coverage .
How the signalling messages flow between originator and receiver for both are scenarios ?
