User blog comment:Zathronas/Speculative Author - RWBY Relativity/@comment-25396609-20160225025456/@comment-25396609-20160225052958

Four massive radio broadcasting towers, equipped with extremely powerful (likely dust bsed) amplification systems, and paired with relay systems at strategic points to extend the reach of the signal.

The logistic of building systems like that are insane, and you do need a lot of technological advancement and specific technologies to be able to execute it safely (read; without giving literally everybody cancer/melting their brains) which is where the scientific advancement comes in.

Either that, or light based transmissions. (Li-Fi, google it)