noise reduction questions

[Dan Sawyer <earthlink.net; dansawyer@xxxxxxxxxxxxxxxx>]

Leif,

I am interested in the basic theory and state of implementation for 
noise reduction. What is the basis of current implementations and what 
are the limits?

Are current limits based on simple filters or has it progressed to noise 
identification and cancellation?

How good is I Q filtering? How does it identify noise from signal?

Sorry to start at such a high level, however the available articles seem 
to jump into the middle.

Thanks,

Dan

LINRADDARNIL