Iterative Detection and Phase Recovery for Downlink DS and MC-CDMAFlat Rayleigh Fading Channels

In this paper, iterative detection is applied in the receiver for downlink of both direct sequence (DS) and multi-carrier (MC) code division multiple access (CDMA) systems in the flat Rayleigh fading channels. A joint iterative detection and phase recovery scheme is proposed. Unlike the conventional bit-interleaved coded modulation with iterative decoding (BICM-ID) structure, the proposed receiver feeds the extrinsic information from soft-input soft-output (SISO) decoder back to update both the adaptive minimum mean squared error (MMSE) correlator and phase locked-loop (PLL) instead of de-mapper. We also investigate how the second-order PLL benefits from the iterative process over the time-varying flat Rayleigh fading channel. Simulation results illustrate that the iterative process significantly improves the performance of the adaptive detector by suppressing multiple access interference (MAI). Additionally, the tracking capability of PLL is enhanced by reducing the equivalent noise power.