Mr. Zubrin states in his book THE CASE FOR MARS that VHF/UHF surface communications (which are basically line of sight) will be severely restricted because of the smaller diameter of the planet, and therefore the much closer horizon. He also states that satellite communications will be very expensive and therefore not a viable option for some time to come. But, he says, high frequency (HF) single side band voice transmission, like the amateur radio community uses for world wide communication, should be possible since Mars has an ionosphere as does the earth. Scientists exploring a new world won't be satisfied with just voice communications. They will really need digital communication; direct error free transmission of computer data files etc. If surface to surface HF SSB voice communication is possible on Mars, so is error free digital communication. The hams are doing it now on this earth and the technology is being applied world wide commercially where Internet telephone communication is unavailable and satellite technology is too expensive. All that is needed are the SSB radios that Zubrin mentioned, a computer board (and the computer of course), the software, and three audio cables.

Computer and Communications Infrastructure