Noncoherent detection of DQPSK in OFDM systems using predictive VA

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Noncoherent detection of differential quaternary phase shift keying (DQPSK) signals in OFDM systems is efficiently implemented using a predictive Viterbi algorithm (VA) operating on a trellis with just ST = MP−1 states instead of MP states, where M denotes an M-ary PSK constellation and P denotes the order of the prediction filter. The prediction filter coefficients are generated based on the channel DFT alone making a high SNR approximation, since the estimation of the noise-variance using training symbols results in loss of throughput.