Contents 1. INTRODUCTION
Orthogonal Frequency Division Multiplexing (OFDM) corresponds to a multi-carrier modulation (MCM) scheme that is now widely used for signal transmission over multipath fading channels. Indeed the decomposition of the OFDM signal over several narrow frequency bands is an appropriate technique to fight against the frequency selectivity that is inherent, for instance, to the mobile radio channel. However, even if OFDM is now part of various transmission standards [1], it still presents some limitations. Indeed, conventional OFDM is based on a rectangular pulse shaping that naturally leads to high out-of-band energy radiations. In order to improve the spectral properties, a pulse shape, i.e. a prototype filter, has to be introduced. An appropriate scheme for that is based on the OFDM/OQAM modulation, where each subcarrier is modulated with a staggered Quadrature Amplitude Modulation (QAM), also called Offset QAM. The basic concepts of OFDM/OQAM can be found in [2]. But it is more recently [3]that OFDM/OQAM has been presented as a viable alternative to OFDM that could also be based on Fast Fourier Transform (FFT) algorithms and simplified equalization [4]. Compared to conventional OFDM that transmits complex-valued symbols at a given symbol rate, OFDM/OQAM transmits real-valued symbols at twice this symbol rate and therefore has a similar spectral efficiency. Furthermore, in practice, it may provide a higher useful bit rate since it operates without the addition of a guard interval or cyclic prefix (CP) [3], [5], [6].
