How do communications work in Star Wars?

My previous question Why does Binary exist? started a conversation which led me to this new question: How do long-range communications work in the first place? (I was wondering why droids had to speak Binary instead of using existing technology for other communication modes humans and other tech already use, then a range of problems are highlighted, but I wonder how much of those problems do indeed exist in Star Wars)

HoloNet transmissions, for one, are transmitted over hyperspace. So the question is:

• How much do galactic communications rely on the hyperspace medium?
• Are communication methods over the EM spectrum used? How are the technical problems with using that spectrum in space (mentioned in the chat in the linked question) overcome?

OK, so some form of answer has addressed the hyperspace part. Focusing more on sublight and EM communications:

• The main issues mentioned were the same as what we can expect in real life: spectrum crunch and background noise, both from cosmic sources and from millennia of galactic use. How are these addressed?
• With inter-system communications using the hyperspace medium, we can assume they do not contribute to the problems stated, leaving only infra-system communications. The parties involved would be static users (local inhabitants and infrastructure) and temporary users (starships passing through the system).
• Therefore, the first problem that needs to be overcome is spectrum crunch between these users (I would venture that more futuristic tech allow the same spectrum to be divided between more users, so this may not be as serious a problem to them as it may be to us)
• The more serious problem would be handling incoming noise from outside the system and (as any responsible person should do) isolating outgoing noise from leaving the system