Iterative Channel Estimation for Space-Time Coded MC-CDMA

This paper investigates a downlink multiple-input multiple-output (MIMO) multi-carrier code division multiple access (MC-CDMA) system with iterative channel estimation (ICE) in the receiver. In MC-CDMA, each user´s data symbols are spread with a Walsh-Hadamard code. Due to the superposition of different users´ spread data signals, zero-valued subcarriers can occur, which cannot be used to compute least-squares (LS) estimates in ICE. For multiple transmit antennas, the data signals coincide non-orthogonal at each receive antenna. Hence, we propose two MIMO channel estimation methods to overcome these problems and avoid noise enhancement in ICE.