Patent ID: 7433428

Claim:
A METHOD OF REDUCNG THE VARIANCE OF THE SIGNAL-TO-NOISE RATE ESTIMATED FOR A SIGNAL WITH AMPLITUDE DIFFERENTIAL PHASE-SHIFT KEYING MODULATION, applicable to a two-way communication system of multiple sets of user equipment in which amplitude differential phase-shift keying modulation ADPSK is used, which requires a sending of a phase reference symbol prior to sending an information, and where an estimation is made of the signal-to-noise rate in order to use a modulation with a maximum number of bits per symbol, maintaining a bit error probability in reception within certain given margins; said method comprising: receiving a symbol with known modulation (bits per carrier), measuring an amplitude error using an amplitude dectected by an amplitude detector, that is the detected amplitude, over the symbol received, measuring an error in the phase increment using a phase increment detected by a phase detector, that is the detected phase increment, over the symbol received, translocating the amplitude error and the error in the phase increment to a first ring of the constellation, as if the received symbol had been transmitted in that ring, calculating a noise-power as the square of the modulus of the error vector, where said error vector is formed by the amplitude error and the error in the phase increment, where said noise-power is accumulated and averaged; in order to calculate noise samples, reduce the variance of the signal to noise rate and equalize said variance among optimum constellations of odd and even bits per symbol, estimating the signal-to-noise rate with the noise-power previously calculated and the known power of the ADPSK signal, selecting the modulation with the maximum number of bits per symbol keeping probability error of bit in reception inside the given margins using the estimated signal-to-noise rate previously calculated.