As far as I know there is not a Vex rule concerning wifi but it is best practices for the event partner to set that rule concerning 2.4 ghz wifi. We use 5 ghz wifi in the room where the robots compete and do not have problems with interference. Event partners can also use Android devices for scoring using the Vex TM app. It is highly recommended that this is only done with the 5 ghz network.
I do know that the 2.4 ghz wifi networks can interfere with the VexNet control system. That is the main issue. As an event partner, I would not want anyone running anything in that range in the room with the competition fields. As for someone running their own 5 ghz wifi, well, I would not want anything interfering with my wifi on which I am running TM software.
The transmitters and receivers are not why wifi hotspots are highly unrecommended. The main reason is because it may interfere with the competition having a communication with the internet. Basically so much information is being used and transferred from a computer to about 3-7 computers in the game to display, they then simultaneously have to send the information to robotevents, AND they have to be able to send information to everyone to update, download, and receive information from VEX Via.
At nationals last year for NBN, there was around 3 people who made a wifi hotspot, and someone said from the loudspeaker “Please turn off your wifi hotspots.” After about ten minutes, I check my wifi and the first hotspot on top was named “Everyone Turn on your Hotspot.” After another ten minutes, there was about a total of TWENTY-TO-THIRTY WIFI HOTSPOTS THAT ARE ON AT NATIONALS… Fun times, even though it was dangerous…
My final goal is to create a system to locally share scouting data, my options are bluetooth, a local wifi network, wifi-direct communication or a base station at our pit that our scouts have to plug into to offload/get new data. Obviously the wired connection is less desirable and bluetooth has a pitifully short range, never seems to work properly with automated connections and has a limit of 7 simultaneous connections. I would suspect running something over the 5 GHz band wouldn’t provide that much interference with the competitions own network as I would be transmitting very little data and wifi was designed to remain functional with crowding. Please correct me if I’m wrong about any of these points.