Channel estimation with power-controlled pilot symbols and decision-directed reference symbols [OFDM systems]

In this paper, a new channel estimation technique is presented that can improve the performance of channel estimation with fewer pilot symbols transmitted than would be normally required in the conventional techniques. In the proposed technique, temporary estimates of CSI are initially obtained based on the transmitted pilot symbols and used to create additional decision-directed reference symbols (referred to as virtual pilots) with the least-square estimation technique. The proposed technique is differentiated from existing decision-directed channel estimation techniques in that the blind decision process for data symbols is incorporated to increase the total number of pilot symbols, instead of directly using the decision-directed CSI estimates. In order to enhance the quality of the demodulated data symbols that may be selected as virtual pilot symbols, transmit power control can be employed on the transmitted pilot symbols. From computer simulation, it is observed that the proposed method outperforms the conventional method and achieves about 3 dB gain for QPSK and more than 5 dB for 16-QAM at an SER of 10^-2 in the channel model considered.