Time- and Frequency-Domain-Spread Generalized Multicarrier DS-CDMA Using Subspace-Based Blind and Group-Blind Space–Time Multiuser Detection

Subspace-based blind and group-blind space-time (ST) multiuser detection (MUD) is invoked for a smart-antenna-aided generalized multicarrier direct-sequence code-division multiple-access (MC DS-CDMA) system communicating over a dispersive ST Rayleigh fading channel, where the channel estimates are attained by using subspace-based blind techniques. Smart antennas are employed to provide increased degrees of freedom and, hence, to improve both the attainable single-user performance and the multiuser capacity. Furthermore, two adaptive subspace-tracking algorithms, i.e., the projection approximation subspace-tracking deflation (PASTd) algorithm and the noise-averaged Hermitian-Jacobi fast subspace tracking (NAHJ-FST) algorithm, are employed for the sake of reducing the computational complexity imposed by eigenvalue decomposition. When employing the NAHJ-FST algorithm, the group-blind MUD employing an antenna array having M = 2 elements exposed to uncorrelated fading achieved a 4.2-dB signal-to-noise-ratio (SNR) gain at a bit error rate (BER) of 10^-4 compared with that employing a single antenna, which is an explicit benefit of its increased computational complexity.