Multistage MMSE weighted decision feedback multiuser detector for DS-CDMA and MC-CDMA

This paper proposes the MMSE weighted decision feedback (WDF) multiuser detector (MUD), which is an enhancement of the MMSE decision-feedback MUD. In contrast to MMSE-DF MUD, in MMSE-WDF past decisions are scaled by weighting factors that reflect their reliability. Furthermore, a multistage structure is utilized to improve the decision quality. An algorithm is also presented for jointly optimizing the reliability weighting factors and the coefficients of feedforward and feedback filters for every stage. Simulation results show that some variations of MMSE-WDF perform very closely to the single-user bound for E_b/N₀ lower than 25 dB and the number of active users less than 30.