Weighted circularly convolved filtering in OFDM/OQAM

A novel technique for removing the edge time transitions, a.k.a. tails, as well as the half symbol offset overhead of OFDM/OQAM signal is proposed. The proposed technique, which is called weighted circular convolution, totally removes the signal overheads, while preserving the real-orthogonality of the prototype filter, and as such, does not incur any ISI/ICI on the demodulated OQAM symbols. It is based on extension of the finite-length OQAM sequence to infinite-length such that the resulting signal is periodic. This periodicity together with special structure of OFDM/OQAM enables one to transmit only the desired overhead-removed portion of signal. This is equivalent to a weighted circular convolution instead of linear convolution in the OFDM/OQAM modulator/demodulator. The spectral sidelobe augmentation due to the sharp edge transitions of the overhead-removed signal is resolved by a weighted time-domain windowing. The proposed overhead-removal technique is applicable to an OFDM/OQAM burst of arbitrary length (either even or odd) and, among other benefits, significantly improves the spectral efficiency especially for short-burst signals.