Enhanced blind subspace-based signature waveform estimation in CDMA systems with circular noise

A new subspace-based blind algorithm for signature waveform estimation in direct-sequence code division multiple-access (DS-CDMA) systems is proposed. Our technique represents a generalization of the popular technique by H. Liu and G. Xu (see IEEE Trans. Communications, vol.44, p.1346-54, 1996) and additionally exploits the non-circularity of the transmitted signals and the circularity of noise to increase the dimension of the observation space twice while keeping the dimension of the signal subspace unchanged. This leads to a substantially improved performance of the proposed algorithm and enables it to be applied to scenarios with larger numbers of active users and lengthier user channels as compared to the original algorithm by Liu and Xu.