Automatic dependent surveillance-broadcast
 

ADS-B is leading to Free Flight ... so here few questions:

1. Time-line of global implementations;
2. Basic principal and very basic theory of operations.

1. don't have any idea.

2.what I read somewhere, it uses the GPS, then it transmitting (broadcast)the information (flight ID, direction of flight, speed,etc) to other traffic and some ground base station as well.

I imagine this would be a radar_like display for pilot.

1- mostly used as I know in the orient for high altitude reporting... Will be a slow implementation into congested functions.

2- take another responsibility/liability from the pilot/airline. As is now it reduces problems due to language communications, one day i see it recieved by fms and commanding flight environment changes.

Here is a link to a quite comprehensive explanation (in reasonably simple terms) at Wikipedia. It's not a scholarly or technical article, but I think it will provide the information you are seeking.

Both of your questions (what is it, and what is the timeline) are answered in the Wikipedia article.

Michael