Orthogonal Frequency Division Multiplexing Based on Offset-QAM

H. Bölcskei

Communication Technology Lab, Swiss Federal Institute of Technology (ETH), Sternwartstr. 7, CH-8092 Zürich, Switzerland
email: boelcskei@nari.ee.ethz.ch

One of the factors determining the performance of wireless Orthogonal Frequency Division Multiplexing (OFDM) systems is time-frequency localization of the transmitter and receiver pulse shaping filters. OFDM based on offset quadrature amplitude modulation (OFDM/OQAM) bypasses a major disadvantage of OFDM based on ordinary QAM, namely the fact that time-frequency well-localized pulse shaping filters are prohibited in the case of critical time-frequency density where spectral efficiency is maximal. In this chapter, we study the problem of pulse shaping filter design for OFDM/OQAM systems and we establish relations between OFDM/OQAM and Wilson and Gabor expansions. We derive general orthogonality conditions for OFDM/OQAM systems and we propose a computationally efficient method for designing time-frequency well-localized OFDM/OQAM pulse shaping filters with arbitrary length and arbitrary overlapping factors. We furthermore introduce biorthogonal frequency division multiplexing based on OQAM (BFDM/OQAM). Finally, design examples are presented to assess the performance of the proposed design algorithm.