COMMUNICATION FAILURE

    If communication beetwen pilot and ATC,the aircraft position on air the same meaning"AIR-GROUND COMMUNICATION FAILURE ANSD GROUND-GROUND COMMUNICATION FAILURE" How does the pilot communicate with ATC if events like this ?
First,the pilot set SQUAWK number on freq 7600,and if the aircraft position on vicinity aerodrome then ATC used GUN LIGHT for controlled the aircraft .

ATC GUN LIGHT SIGNALS
COLOR	GROUND	AIR
STEADY GREEN	CLEAR FOR TAKE OFF	CLEAR TO LAND
FLASHING GREEN	CLEAR TO TAXI	RETURN TO LAND
STEADY RED	STOP	GIVE WAY TO ANOTHER AIRCRAFT
FLASHING RED	TAXI CLEAR OF RUNWAY	AIRPORT UNSAFE-DO NOT LAND
FLASHING WHITE	RETURN TO STARTING POINY ON AIRPORT	NOT AVAILABLE