Alternative Subspace Method for Improved Blind Channel Estimation in Uplink Zero Padded MC-DS/CDMA Systems

This work investigates the problem of uplink blind channel estimation in zero padded multi carrier direct sequence code division multiple access (MC-DS/CDMA-ZP). Using only the spreading code of the user of interest, our method explores the orthogonality of the signal and noise subspaces in conjunction with power techniques to estimate the channel state information (CSI) from the received data sequence. We also present an improved channel estimator that relies on the assumption that all the relevant multipath components of the channel impulse response lie within the guard interval duration. Simulations of mean square error and bit error rate performances demonstrate the robustness of the proposed scheme, and for moderate-to-high signal to noise ratios the presented method achieves performance comparable to existing subspace techniques but at a softer computational cost.