Efficient implementations and alternative architectures for OFDM-OQAM systems

We derive new implementations for baseband and passband orthogonal frequency-division multiplexing based on offset QAM (OFDM-OQAM), which nearly halve the number of arithmetic operations required every symbol period by exploiting the symmetries in the transmitted sequences. We also propose a novel scheme, named conjugate, that employs two different filters being the time-reversed version of each other: one in the modulator for the even subchannels and in the demodulator for the odd ones, and the other in the modulator for the odd subchannels and in the demodulator for the even ones. We formulate both baseband and passband versions of this scheme in which the constraints for the filter design are loosened, requiring only amplitude tailoring of its frequency response. We derive efficient implementations for the conjugate scheme, which exhibit a significantly lower complexity than previous implementations of the traditional OFDM-OQAM scheme.