Abstract: Method of communicating digital data in which frames (8) are transmitted cyclically whereby a first number of symbols is transmitted according to a first keying mode (II) using a first constellation, and a second number of symbols is transmitted according to a second keying mode (L) using a second constellation. The first and second keying modes (H, L) are used at predetermined positions in the frame, whereby both the symbols according to the first and second keying mode carry information under at least an operative traffic phase.

Abstract: According to the invention, a fade margin test value for a radio link is calculated according to a routine whereby the output power of the transmitter is gradually decreased until the forward error correction activity FCA reaches a predetermined value, FCA1, whereupon the output power is regulated back to a duty level again. The reduction in output power is performed when the link is operating in a normal way, i.e. while communication may be transmitted on the link. Subsequently, a fade margin test value FM is determined as the ratio related to the nominal output power and the output power corresponding to the predetermined forward error correction value FCA1 at the reduced power level. Finally, the output power is increased to nominal output power.