I think the key thing is that IR allows the bands to work regardless of where the wristbands are located in the stadium. Additionally, they're probably using the IR to multiplex since the DMX 512 standard technically only supports 512 channels (which if each device uses a channel for color and channel for intensity, is only 256 supported devices).
With the IR technology, they are not addressing the individual lights. The bands just respond when IR splashes on them. The IR "spotlight" is just transmitting a command on repeat, and the bands display that one off command. DMX is just commanding the spot to move a certain way, and transmit a certain code.
They have a RF variant where they put the bands on each seat before the show. THOSE bands are individually addressed with RF, and their position known in advance to the setup. (If you move a band to another seat you'll mess it up). They have a special device that transmits RF across the whole venue. That device probably has a DMX hookup to take commands to transition to certain pre-programmed scenes and/or animations, and commands from a USB-connected PC.
It sounds like each band can be a part of (at least) 2 "groups", with the example showing groups 1-18 assigned to each stadium section, and 1-9 going all the way around from the first row to the highest/back row.
It's not hard to imagine that they've mapped each of those groups to a DMX channel, with the value indicating the color, and/or flash pattern, etc. Even if you're limited to 512 distinct groups (a single DMX universe), that's a lot of granularity. With that, any lighting designer/operator can use their console of choice to do scene and sequence programming -- no special training needed.
Yea, that sounds sane. The RF transmitter gets the DMX commands to groups, which then get translated to batches of RF bands, and then they just act on that.
I wonder if the RF system has enough bandwidth to show a movie or an animation at a decent frame rate, because that would be a neat effect.
IR has arbitrarily good spatial bandwidth — instead of a conventional moving light setup, it could be done like a projector — stick a DLP chip or an LED array at the focal plane. Then you could project a movie by literally projecting the movie as IR commands :)
