Apparatuses of user equipment (UEs) for end-to-end coordination of voice over cellular data network communications. An apparatus of a UE includes one or more data storage devices and one or more processors. The one or more data storage devices are configured to store delay budget information pertaining to end-to-end delivery of a real-time transport protocol (RTP) stream sent from a remote UE to the UE. The one or more processors are configured to generate an application layer message including the delay budget information, the application layer message to be transmitted to the remote UE to enable the remote UE to request, from a cellular base station servicing the remote UE, additional air interface delay based on the delay budget information.