Near-far resistant receivers without a priori synchronization for asynchronous DS-CDMA systems

A receiver for data demodulation in an asynchronous direct-sequence code-division multiple access (DS-CDMA) system without prior knowledge of the propagation delays is proposed. Special attention is paid to the near-far problem and the proposed schemes are experimentally shown to be near-far robust. The near-far robustness is obtained by estimating the a priori unknown propagation delay using a subspace based technique. Quantities obtained in the estimation procedure are subsequently used to design a filter, used for suppression of interference, according to the minimum mean-squared error criterion. A simple two-state Viterbi algorithm is used for the data demodulation.