Differentially coherent demodulation for differential BPSK in spread spectrum systems

A demodulator for differential phase-shift keying is proposed, which outperforms significantly the noncoherent receiver. It is based on coherent demodulation with decision-directed channel estimation followed by differential demodulation. The metric for maximum-likelihood decoding is derived. The performance is estimated for spread spectrum communication on frequency-selective Rayleigh fading channels. It is demonstrated that the proposed demodulator is attractive in particular for systems with low maximum Doppler frequency.