Detection of cooperative OFDM signals in time-varying channels with partial whitening of intercarrier interference

Cooperative communication can yield spatial diversity gains, but its performance can also suffer severely from the multiple carrier frequency offsets (MCFOs) induced by high-speed relative motion, in addition to Doppler spread. In orthogonal frequency-division multiplexing (OFDM) systems, such performance degradation arises as a result of intercarrier interference (ICI). We have shown previously that, in conventional non-cooperative communication, certain ICI components (called residual ICI) display high normalized autocorrelation and a partial whitening of the residual ICI can significantly benefit OFDM signal detection. In this work, we show that similar whitening can also be employed in cooperative communication to address the MCFO issue mentioned above. As an illustration, we simulate a distributed spatial-frequency block coding (SFBC) OFDM system subject to highly disparate MCFOs, where in the receiver we perform partial whitening of the residual ICI followed by maximum-likelihood sequence estimation (MLSE). The results show that the proposed method can comfortably accommodate a maximum MCFO span well exceeding one subcarrier spacing.