MCM-DSSS with DPSK modulation and equal gain combining in Doppler-spread Rician fading

A method for computing the bit error probability (BEP) of multi-carrier modulated (MCM) direct-sequence spread-spectrum (DSSS) using differentially coherent phase-shift keying (DPSK) with equal gain combining in Doppler-spread Rician fading is given. It is based on Gauss-Chebyshev quadrature integration of the moment generating function of the decision statistic at the combiner output. The results show that as the specular to diffuse power ratio, K, increases the crossover points of the BEP curves for various orders of diversity (number of MCM carriers) occur at increasing values of average energy per-bit-to-noise spectral density ratio (SNR). Thus, for low to moderate SNRs, increased diversity may not give improvement while, for sufficiently high SNRs it does