A Low Complexity Downlink Beamforming Scheme for DS-CDMA System

The downlink capacity of frequency division duplex (FDD) based DS-CDMA system can be improved if multielement antenna array is equipped at the base station. In this paper, a novel two-path downlink beamforming (TPDB) scheme is proposed to reduce multiple access interference as well as providing two-order path diversity in downlink. An analysis model is presented for the capacity evaluation of multirate DS-CDMA system with base station antenna array, and the capacity performance of the TPDB is compared with other schemes based on this model. The comparison results show that the TPDB would be a promising candidate for the downlink transmission if both performance and implementation complexity are considered. Moreover, a simple algorithm is proposed for the steering vector estimation in the TPDB, and the robustness of this estimation algorithm in the presence of fading and interference is also confirmed by computer simulations.