A decision aided CDMA receiver with partially adaptive decorrelating multi-user interference cancellation

Abstract

A CDMA receiver with enhanced multiple access interference (MAI) suppression is proposed for a pilot symbols assisted system over multipath channels. The design of the receiver involves the following procedure. First, blind adaptive correlators are constructed at different fingers based on the scheme of generalized sidelobe canceller (GSC) to collect the multipath signals and suppress MAI. A low-complexity partially adaptive (PA) realization of the GSC correlators is proposed which incorporates multi-user information for reduced rank processing. By a judiciously designed decorrelating procedure, a new GSC structure is obtained in which the MAI are decorrelated and suppressed individually. The next step is then a simple coherent combining of the correlator outputs with pilot aided channel estimation. Finally, further performance enhancement is achieved by an iterative scheme in which the signal is reconstructed and subtracted from the GSC correlators input data, leading to faster convergence of the receiver. The proposed low-complexity PA CDMA multi-user receiver is shown to be robust to multipath fading and channel errors, and achieve nearly the same performance of the ideal maximum SINR and MMSE receivers by using a small number of pilot symbols.