What if the building is intentionally built as a Faraday Cage thus preventing an outside signal? This way the signal is passively blocked and they can still provide their wifi inside.
You can still bring the wifi antennas inside the venue and operate a wifi LAN.
The cage may block avenues for that LAN's access to the Internet, but in the worst case scenario, someone could operate a sneakernet bridge by shuttling large storage devices between the wifi LAN inside the doors and the WAN access point outside them. Latency would be terrible, but you could get the packets through eventually.
I think this would be a disaster for other reasons and EM bands. Doctors with Pagers. Parents who need to be informed of a sick kid at school, etc. You would be interfering with a public conveyance.
Many convention centers are, nonetheless, obviously built to ensure you won't get a signal inside the building and will have to pay for whatever overpriced service the convention center offers.
Even from a cynical-greed perspective, that seems catastrophically stupid. Businessfolks need to stay in touch. A convention center where cellphones don't work is a convention center that won't get a lot of repeat customers, and cellphones don't even offer the option of extorting your visitors to use your in-house service like wifi does.
Sure it does. Have your venue be a faraday cage so that outside cellular service doesn't work inside. Setup cellular service inside your building, and enter into high cost roaming agreements with the major carriers, at such a rate that the carriers pass it on to customers. Much like cell service on cruise ships.
Can you imagine the public outrage when people start finding $100 roaming charges on their cellphones because they stayed at a hotel? And the alternative is to notify all your potential customers that their phone costs more inside this building, before they actually give you any money. Your competitors would throw a party when they heard about it.
The reason why building to block cellular is important is that many conventions would otherwise bring in cellular modems to provide internet access. Without cellular signal, they have to pay the convention center for internet access.
(for phone service, people just have to give up and go outside)
Not that I condone their behavior.