Robust Transmission Over Fast Fading Channels on the Basis of OFDM-MFSK

We present an OFDM-based transmission scheme which is suitable for robust transmission in fast fading environments, where a reliable channel estimate is impossible or very difficult to obtain. Our scheme is based on the combination of noncoherently detected M-ary frequency shift keying (MFSK) and orthogonal frequency division multiplexing (OFDM). Noncoherent detection of OFDM-MFSK allows an arbitrary phase choice for all subcarriers in the transmitter. One possibility to exploit this degree of freedom is to choose the subcarrier phases such, that the peak-to-average power ratio (PARR) is reduced. A second possibility is to use the subcarrier phases to transmit additional data. This can be done by differentially modulating the subcarriers that are occupied by the OFDM-MFSK scheme. Both possibilities do not affect the robustness of the underlying noncoherently detected OFDM-MFSK modulation.