The LA convention center should already have all that in place and available for rent/usage during your event.
That said in order to put your own WiFi system into place you’ll need to bunch of WiFi access ports and a network router to route the network traffic from the wireless network to the public Internet.
To cover both the buildings of the LA convention center you’ll probably need 100+ access points as the facility is quite large (I’ve there all the time for Microsoft events).
The network will need to be setup with probably a class B private IP subnet so that there are enough IPs for everyone and every device that will need to get on the network.
As for RFID you’ll need to mount RFID scanners on the doors and anywhere else that you want to capture the traffic, and have a way for that data to get to a central system so that you can do something useful with it.
you can as well implement wireless mesh….as said the LA arena is large so you will need like 5 mesh routers for your backbone..also use multi radio routers..so your back bone can be on a radio and you connect clients on another network….am doing researches on secure routing protocols but i guess you could implement any of the adhoc routing protocols…bout ip addressing..mesh routers have self-forming self-configure,self-healing abilities so you don’t worry about them forming up but the clients you could assign a class b like said earlier but you would need a dhcp server for that and since you using that you could do your RFID and as well implement 802.1x security for the network….i don’t mind if any body can get me an insight about secure routing in wireless mesh network’s researh questions…cheers