Downlink MC-2D-CDMA over Time-Variant Frequency-Selective Rayleigh Fading Channels

In this paper, the performance of a downlink synchronous MC-CDMA system with joint frequency-time domain spreading over time-variant frequency-selective Rayleigh fading channels is investigated. We propose an adaptive two dimensional MMSE (minimum mean square error) receiver, which works in decision-directed model after the initial training period. Due to the time variability, a subcarrier phase tracker, which comprises a bank of phase locked-loops (PLLs), is employed in the proposed receiver to track the fading phase variability. Furthermore, a simplified phase tracker structure is proposed to reduce the complexity of system. The theoretical bit error rate (BER) is derived and simulation results indicate that the proposed receiver can achieve good frequency diversity and subcarrier synchronisation, compared to the conventional MCCDMA structures.