Iterative Detection Aided DL SDMA Systems Using Quantized Channel Impulse Response

An iterative detection aided Down-Link (DL) Space Division Multiple Access (SDMA) system is proposed. The Base Station (BS) requires DL Channel State Information (CSI) estimated by and fed back from the Mobile Station (MS) for separating the DL signals to be transmitted to the MSs from the BS. The authors investigate the achievable system performance subject to finite-accuracy CSI feedback. The achievable receiver performance is investigated with the aid of EXtrinsic Information Transfer (EXIT) Charts. Furthermore, a novel concept, referred to as the EXIT-Chart Optimized CSI Quantization (ECO-CQ) is proposed. The ECO-CQ scheme assists the system in maintaining the lowest possible CSI feedback overhead, while ensuring that an open EXIT-tunnel is still attainable, which implies maintaining an infinitesimally low BER.