A unified framework for the construction of OFDM/OQAM systems

OFDM/OQAM is a promising radio access technique for high data-rate fourth generation cellular systems, operating on time and frequency dispersive wireless channel. Contrary to the well established OFDM/QAM, it allows very well localized prototype waveforms to be used for critical unit-density time-frequency lattices, offering maximal spectrum efficiency. Starting from the set of orthonormality conditions verified by the frequency-time lattice shifted versions of the prototype waveform, we derive the general orthonormality criterion for OFDM/OQAM. We show that even and odd parity prototype waveforms are basically the unique waveforms for which the general orthonormality criterion simplifies to that of OFDM/QAM with frac12 time-frequency lattice density. Based on the simplified criterion, we propose and characterize a new orthonormalization procedure for the efficient design of very well localized prototype functions, starting from non-orthogonal mother waveforms. Finally, we show that odd parity orthonormalized mother functions lead inevitably to badly localized prototype waveforms and that only even parity prototype waveforms should be used in practice.