Coherent and differentially coherent detections of orthogonally multiplexed orthogonal phase-modulated signals

The family of orthogonally multiplexed orthogonal phase modulations (OMOPMs) is investigated in this paper. Both coherent and differentially coherent signaling formats are considered and compared with the recently reported orthogonally multiplexed orthogonal amplitude-modulated (OMOAM) signals. When constructed from the same basis set, both OMOPM and OMOAM signals exhibit the identical power spectral density and, thus, the similar spectral performance characteristics. Based on the maximum-likelihood principle, coherent and differentially coherent detection algorithms are developed. Tight approximate upper bounds are derived and verified by simulation to evaluate the bit error probability characteristics of the maximum likelihood algorithms. It is shown that both coherent and differentially coherent OMOPM can provide a great choice of power and spectral efficiencies ranging among the efficiencies achieved by the classical modulations based on the orthogonal multiplexing technique.