OFDM Channel Estimation for the Amply-and-Forward Cooperative Channel

OFDM can significantly reduce the receiver complexity by using one-tap equalizer in frequency selective channels, and it can be enhanced the capacity and diversity by using cooperative scheme. However, high data rate transmission with OFDM requires the channel state information (CSI), and therefore OFDM channel estimation for cooperative communication can be a challenging problem. In this paper, we investigate the OFDM channel estimation suitable for the amply-and-forward (AF) cooperative channel. Cramer-Rao lower bound (CRB) of the estimation is derived, and optimal preamble conditions that minimize the CRB with several power constraints are proposed. Moreover, minimum variance unbiased (MVU) estimator that achieves the CRB is introduced for the cooperative channel. Simulations with analytical results confirm the performance of our methods.