That’s a major part in the Ender’s Game series. They have faster than light communication, but the ships travel at like 90% the speed of light. So when traveling between planets, it’s like a two week trip to the people traveling, but 20 years on planet.
The main character Ender travels often, so he is only 35 in the second book, a couple thousand years after the first book.



https://en.m.wikipedia.org/wiki/Multimedia_over_Coax_Alliance
Similar idea to powerline adapters, except over coax lines instead.