-I consider a digital broadcast (radio) transmission
-I consider the reception of this broadcast signal at a relay
The first task to consider is to compute the link budget analysis of the radio link between the transmission site and the reception site.
This will consider propagation, attenuation, interference, etc.
Then you can look at the type of traffic and its tolerance to transmission error patterns.
That's what I would do: satellite or terrestrial broadcast. For multicast you can have a similar approach looking at the link and then packet types, and error patterns types. The problem, once structure in that way, is easier to address.