A decision-feedback equalizer with tentative chip feedback for the downlink of wideband CDMA

We investigate a chip-level minimum mean-square-error (MMSE) decision-feedback equalizer (DFE) for the downlink receiver of wideband code-division multiple-access (CDMA) systems using long scrambling code over frequency-selective channels. The DFE uses the tentative decision of the current symbol as feedback. The proposed DFE performs better than the chip-level linear equalizers (LE) and the DFE that feeds back only the symbols already decided. The performance gain increases with signal-to-noise ratio (SNR), but decreases with the number of active users. The performance of these different equalizers is compared through simulation of symbol-level MSE over a fixed channel