How do we get the convention center to stop blocking cellular signals?

I think it's more the fact that 30k people are competing for service in a very small area. Infrastructure isn't designed to accommodate that unless it's a football stadium or something like that where they expect that kind of crowd on a regular basis

Its the stucture, not the center . Some rooms have good signals , some do not. I had a better signal this year than 2 years ago, and it's the same phone in the same room

I was just there a few weeks ago and did not have any issues. They don't block signals in this manner.