A mew MMSE based cascade filter MUD tracking mode in time-varying channels

In direct-sequence code division multiple access (DS-CDMA) systems, performances are limited by multiple access interference (MAI) and intersymbol interference (ISI). To mitigate these interferences and hence increase the capacity and allow high data rates, multiuser detection (MUD) techniques are used. In time varying channels, the MUD´s parameters have to be tracked continuously in order to cancel efficiently the different interferences. Motivated by the fact that minimum mean square error (MMSE) based receivers allow significant gain in performances and that decision directed adaptive linear MMSE (DD-AL-MMSE) receivers show poor performances specially in a fast fading environment, a new tracking mode of the two-stage linear cascade filter MUD (CF-MUD) is proposed in this paper offering a good trade-off between performance and complexity. A comparative study analysis of different receivers is conducted, including AL-MMSE and CF-MUD with and without decision directed scheme.