Principal component combining with differential detection for DPSK signals over Rayleigh fading channels

A principal component combining with differential detector (PCC-DD) is proposed to demodulate M-ary DPSK signals in diversity systems. Exact average bit error probability (BEP) of binary DPSK signals over Rayleigh fading channels for the PCC-DD is obtained in closed form and is shown to agree with the results of simulations. Approximate average BEP of quadrature and octal DPSK signals over Rayleigh fading channels for the PCC-DD are also derived and are shown to be close to those from simulations. It is also shown that PCC-DD outperforms the well known DPSK demodulator that contains a set of differential detectors followed by equal gain combining (DD-EGC) over Rayleigh fading channels in terms of low-average BEP. The performance gain of the PCC-DD over the DD-EGC is large when the signal is binary DPSK, and is very small when the signal is either quadrature or octal DPSK.