An improved blind adaptive multiuser detector in multipath CDMA channels based on subspace estimation

An improved blind adaptive multiuser detector based on subspace estimation is presented for code division multiple access (CDMA) systems. Several adaptive multiuser detectors based on subspace estimation have been proposed, which can offer substantial performance gains over previous adaptive detectors. However their performance always suffers from the subspace rank mismatch, low SNR and insufficient data. The main reason is that the estimated signal subspace may lose a lot of component of the desired signal when the detectors are adaptively implemented under these conditions. Motivated by this, an improved detector making use of the spreading sequence of the desired user to protect the desired signal from loss is proposed with little complexity increase. It can be more robust under the mentioned conditions. Numerical results are provided to support our claims.