A subspace projection based blind interference cancellation scheme for W-CDMA downlink

Blind intra-cell interference cancellation (IIC) of the W-CDMA signal at the mobile unit is considered. A new blind interference cancellation technique, based on the subspace projection approach, suitable for the downlink of any CDMA system is proposed. The receiver is blind in the sense that no prior knowledge of users´ spreading codes or even their spreading factors are required. The mobile receiver estimates the effective spreading codes of the interfering users regardless of their spreading factors using fast Walsh transform correlators and uses these information to cancel out the intra-cell multi-user interference. The complexity of the proposed technique is low compared to conventional interference cancellation techniques. Simulation results show a capacity increase of up to 150 % of the original (without IIC) system capacity or up to 12 dB signal to Gaussian noise ratio gain at a fixed capacity (the inter-cell interference is modeled as Gaussian noise).