Compress and expand the waves. Not suceptable to spikes because height of the wave is not measured. FM waves dont bounce well because they become compressed. You get 4 bits from a single QAM wave, so you can get 19200 from this. See figure 4-12, pg 118.
Bit is a unit of information, baud is a unit of signaling speed.
You should call it BPS, not baud when you refer to a 33600 bps modem. Therefore 3000 baud or bits per second is the theoretical max under ideal circumstances. ITU wants to call baud rate the symbol rate because baud is incorrectly used. Baud assumes NO modulation. BPS is the actual bits per second.