Use of Signals in Quadrature Over OFDM/OQAM

Since more than one decade, orthogonal frequency division multiplexing (OFDM) has been widely selected for radio standards such as DVB-T or IEEE 802.11n. Thanks to the division of the overall stream over the sub-carriers multiplex, high rate transmissions over wide-band channels can be performed while still using a limited complexity receiver. In the following we focus on an enhanced OFDM modulation named OFDM/OQAM. It can reach higher rates as it does not require the use of guard interval. Its main characteristic lies in the fact that the real and imaginary parts of the symbols are transmitted with a time offset corresponding to half the duration of the FFT. As these two parts can also be seen as two successive real-valued symbols we will investigate in this paper on the simultaneous transmission of two OFDM/OQAM signals in quadrature. These two signals will correspond in our study to two users sharing the same channel. At the receive side, we introduce an original receiver based on the turbo-learning principle which iteratively removes the interference terms provided by the proposed OFDM/OQAM scheme. Finally, simulation results over AWGN channel show the interest of our solution.