From what I can tell from the Wikipedia article, Beidou is an active system where the "client" sends data to the satellites in orbit. It makes perfect sense for the Chinese though, because now they can track where their users are -- something not possible with the passive US system since the receivers only receive and can't transmit any data back. In short, Big Brother Beidou always knows where you are.
Seems like an active system has a huge disadvantage, though. You can DOS the satellites by pointing an antenna at each satellite and jamming their uplink frequencies, knocking out the whole system for everyone, everywhere. In the US system, you can only jam local terrestrial reception and anybody over the next hill won't be affected.