A Low Complexity Spatial Rake Receiver using Main Beam Multipath Combining for a CDMA Smart Antenna System

We propose a simple spatial Rake receiver for a CDMA smart antenna system that requires only one beam per user, but still combines multipath. We use an efficient technique based on reduced rank auto-regression (RR-AR) to estimate the directions-of-arrival (DoAs) of the main beam multipath components with very few samples and do soft decision combining; multipath outside the main beam is suppressed by the beamformer. The performance of the new receiver is compared to a conventional receiver which does not combine multipath and the optimum spatial Rake receiver (SRR). The technique greatly reduces the hardware complexity over that of the optimum SRR that requires L beams per user, one for each of the L paths, with ≪ 0.5 dB loss.