Qs re ADS-B technology

Someone gave an ADS-B presentation at our club's meeting last night. It
was terrific, but some interesting questions were asked. I'm wondering if
anyone happens to know the answers or if someone can point me to a
reference.

ADS-B ground stations appear to have a range of about 150 miles, from
what was said. In the area in which we fly (the KEWR class B), that's a
*lot* of aircraft. Assuming all are ADS-B equiped, how does each aircraft
broadcast its information to the ground station?

Is it collision detection like Ethernet? I'd expect a lot of collisions
in this area, thereby slowing the accumulation of information. But a
token-based solution seems a little unwieldy to me given that an aircraft
might be in view of multiple ground stations at any moment in time. More,
aircraft are supposed to broadcast to each other even outside the view of
a ground station. There'd be no master in that case.

So how does that work?

Another question is the broadcasting of the TIS-B and FIS-B information.
Does the ground station just broadcast it all, with the aircraft UATs
determining which (for example) targets are relevant via its GPS location?
How often is a completely broadcast cycle completed? Is this dependent
upon factors like the number of targets visible to the ground station
(ie. the amount of TIS-B information to transmit)?

Thanks...

Andrew