Design of pulse shaping OFDM/OQAM systems for high data-rate transmission over wireless channels

Abstract

Orthogonal frequency division multiplexing (OFDM) is a promising technique for high data-rate transmission over wireless channels. In general, wireless channels are time-frequency dispersive. The performance of wireless OFDM therefore depends critically on the time-frequency localization of the pulse shaping filter used. It has been pointed out in Haas (1996) that OFDM systems based on offset QAM (OFDM/OQAM) bypass a major disadvantage of OFDM schemes based on ordinary QAM, namely the fact that well-localized pulse shaping filters are prohibited in the case of a critical time-frequency grid where spectral efficiency is maximal. In this paper, we derive general orthogonality conditions for OFDM/OQAM systems and we propose efficient (FFT-based) design procedures for time-frequency well-localized OFDM/OQAM pulse shaping filters with arbitrary length and arbitrary overlapping factors. Finally, we present design examples.