Another term commonly used to refer to the medium of communication is

Another term commonly used for the medium of communication is channel, the pathway along which a message travels from sender to receiver.

It names the route or conduit, whether air for the voice, print for the word or cable for the signal, that carries the message across.

Calling it a carrier is loose, since carrier is not the standard paired term the way channel is in communication theory.

Naming it a transporter borrows a logistics word that does not sit in the established vocabulary of the model.

Treating it as a vehicle is a general metaphor rather than the accepted technical synonym for the medium.

Shannon and Weaver fixed channel as the element between transmitter and receiver, cementing it as the medium's standard name.