Performance Evolution for Frequency Invariance for Double Differential Detection System
The Evolution of Multiple Symbol Differential Detection (MSDD) of double differential QAM signal is studied in the presence of frequency offset, phase offset and additive white Gaussian noise. It is shown that in the case of nonzero frequency offset distorts the transmitted signal through attenuating its amplitude and MSDD receiver degrades by increases the number of samples. MSDD signal makes use of maximum like-hood sequence estimation of transmitted phase rather than the symbol by symbol detection as in the conventional differential detection. It is shown that the proposed receiver is robust to the distortions caused by the random frequency variations and a lower bound on the error probability of the proposed MSDD receiver is also derived.