Reduced-complexity equalizer for two-dimensional modulations with coherent demodulation

A reduced-complexity equalizer capable of correcting channel distortion for two-dimensional modulations with coherent demodulation is presented in this paper. Based on the fact that the phase of the in-phase and quadrature sinusoids in the receiver must be synchronized to that of the carrier received, a structure using a pair of real-valued equalizers, one for the in-phase and the other for the quadrature channels, is proved to be appropriate. Conventional approaches in this regard use structures with complex-valued arithmetic and thus call for a much higher computational complexity. Due to the fact that only real-valued arithmetic is needed for the new structure, a saving of 50% multiplications, compared to its complex-valued counterpart, is thus achieved even with better symbol error rate performance. Computer simulation results justify the assertions made in this paper.