Q & A on Using LEO satellites for universal wireless service Q: Sir, sorry to bother you with this - but if global cellular communication is possible using satellites in LEO, why aren't global wireless network connections being set up? Air is a universal medium - therefore, no restriction on a single wire (or several wires) for transmission. Can fixed frequencies be established between two systems that want to communicate such that there won't be interference? This frequency would be fixed, like the NIC address. This would cause security issues, which can also be taken care of - but is this possible? I think I just realized - very sensitive and expensive equipment would be required... A: There are indeed companies using satellite networks as well as companies using terrestrial (i.e., cellular) wireless networks. A: As for your assertions about frequency division multiplexing: although FDM is used in wireless systems, many designs try to limit the number of frequencies used. The reasons are complex (e.g., radio equipment needs a minimum separation between each pair of frequencies to avoid interference, there is a finite bandwidth, and it is much less expensive to build satellites that use a restricted set of frequencies).