I doubt Sat is the solution for 20K users. As to WiFi, when I use that in crowded spaces we end up re-writing our apps to be very robust as well as keeping distances short say as short as 20 feet.
Most of the time I find folk getting into this can't re-write code or even code at all. For them they have to expand the team.
My background involves cellular, wifi and a lot of hardware and code. You sound like you want a ready to use solution, not one where we do the usual million buck development.
Looking for advice regarding placement of atm's at outdoor events (fairs, festivals,etc)Currently, deploy cellular routers, but tower crashes are giving me fits. Thinking Hughes satellite to Engenious MultiPoint to endpoint at atm.Which frequency? 2.4G,5G, 3.6???. Atms connecting to network using DHCP. Some evvents may have 20K participants, so interference issues??Any and all comments welcomed. Thanks, John

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