Adaptive fractionally spaced MMSE receiver for asynchronous DS-CDMA

We present a new adaptive implementation of the linear minimum MSE receiver (LMMSER) for asynchronous DS-CDMA. We show that, in the case of multipath propagation, the optimal LMMSER can be decomposed as a bank of filters followed by maximal-ratio combining of the filtered multipath components, as in conventional RAKE receivers. Each filter in the bank can be adapted by a classical “blind” algorithm, based on the constrained minimization of the mean output energy. Then, the combining coefficients can be estimated by inserting pilot symbols, as in conventional pilot-symbol assisted modulation. Simulations show the effectiveness of the proposed algorithm