Abstract
In order to combat multiple-access interference (MAI) and inter-symbol interference (ISI) in direct-sequence,code-division multiple-access (DS-CDMA) systems under multipath,frequency-selective fading channels,an adaptive decision-feedback equalizer (DFE) is derived using antenna array from the array signal processing point of view in this paper. Throughout the design procedure,the real multipath fading environment is imitated by a time-varying tapped-delay-line (TDL) filter,whose tap coefficients are modeled as auto regressive (AR) processes,with unmodeled dynamic and uncertain noise.A state-space modeling method is developed for antenna array DS-CDMA system to take advantages of the temporal and spatial diversity brought by multipath dispersion and array receiving structure,respectively.A minimax Kalman filtering algorithm,accompanied with the consideration of the worst-case statistics of modeling error and uncertain noise,is employed to efficiently estimate the channel impulse response.Based on the channel estimation,a minimax adaptive DFE receiver is proposed to recover each user's original transmitted symbols as fast and accurately as possible. Performance analysis and some simulation examples are also presented in this study so that the superiority of the proposed robust receiver can be demonstrated.