I was flying under waypoints mode guided by 8-10 Satellites in a park, this morning. After it took off and flew away 300 feet distance, all signal on my cell phone lost except the strong GPS signal. It was under Naza mode. I clicked the Go Home on Ground Station, it said connection lost. Something like GS signal failed, what is GS signal ? I flipped down S1 to failsafe, S2 to HL, nothing happened. On cell phone display, it was flying to next waypoints. It seems that I lost control of it despite it's performing waypoints flying. My questions are : 1) why I was not able to call it home, failsafe or home lock or Go Home on ground station, all failed. 2) why it kept flying to each waypoints when all connection signal were failed ? 3) what can I do to bring it home immediately if I don't feel comfortable when all connection signals are lost during the waypoints flying ? Thanks.