The basics are this, the lower the frequency because lower frequencies propagate better (https://en.wikipedia.org/wiki/Free-space_path_loss https://en.wikipedia

The basics are this, the lower the frequency because lower frequencies propagate better (https://en.wikipedia.org/wiki/Free-space_path_loss https://en.wikipedia.org/wiki/Free-space_path_loss) but... you will get less capacity, because at the lower frequencies there is less spectrum (it is simple arithmetic there is 1000Mhz of spectrum below 1Ghz, but there is 100Ghz of spectrum below 100Ghz (setting aside the details about how it gets allocated etc.) The amount of capacity you can achieve is based on Shannon limit https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theorem https://en.wikipedia.org/wiki/Shannon%E2%80%93Hartley_theore... it's the classic engineering trade off, better propagation vs. more capacity. that is why the carriers want low, medium and high band in their inventory, low is considered < 1Ghz, medium is considered 1Ghz - 10Ghz, high is > 10Ghz, roughly speaking