Iterative Channel Estimation for MC-CDMA
Stephan Sand, Ronald Raulefs, Gunther Auer · 2005
We investigate the performance of a downlink multi-carrier code division multiple access (MC-CDMA) system employing a receiver with iterative channel estimation (ICE). The MC-CDMA system transmits several data symbols per user and per orthogonal frequency division multiplexing (OFDM) symbol in parallel, with each data symbol being spread with a Walsh-Hadamard code. Due to the superposition of spread data signals (chips), zero-valued subcarriers can occur, which cannot be used to compute least-squares (LS) channel estimates in ICE. Therefore, we propose the modified LS and minimum mean square error (MMSE) channel estimation methods to overcome this problem and to avoid noise enhancement in ICE. We compare both methods through simulations and investigate the robustness of ICE with both methods if the channel statistics are not known perfectly.