Design of a low complexity partially adaptive CDMA receiver using conjugate gradient technique

Abstract

A CDMA receiver with enhanced multiple access interference (MAI) suppression is proposed. The design of the receiver involves the following procedure. First, adaptive correlators are constructed at different fingers based on the scheme of generalized side-lobe canceller (GSC) to collect the multipath signals and suppress MAI blindly. In particular, a partially adaptive (PA) realization of the GSC correlators is proposed based on the conjugate gradient (CG) technique. 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, leading to faster convergence of the receiver. The proposed low complexity PA receiver is suitable for downlink CDMA, and shown to outperform the conventional fully adaptive MMSE receiver by using a small number of pilot symbols.