SPC07-6: Iterative Channel Estimation and PAPR Reduction for OFDM System With Overlay Watermarks

We propose a new orthogonal frequency division multiplexing (OFDM) system embedded with overlay training watermarks in this paper. The major advantage of the proposed overlay watermark is the elimination of the in-band OFDM pilots while keeping the peak to average power ratio (PAPR) low for the overlay OFDM signal. As a result, the corresponding spectral efficiency and the transmitter amplifier efficiency are both improved over the existing OFDM systems. The adopted Kasami sequence encrypted overlay watermark is known to the receiver and has very minimal impact on the data detection performance once the channel impulse response is estimated. The proposed channel estimation technique is based on an iterative estimation of the channel impulse response, and the combined signal vector from the overlay pilot sequence and the desired OFDM signal. We also investigate the crucial interfering effect of the overlay pilot on the OFDM signal demodulation. The PAPR of the overlay OFDM signal is analyzed and it is shown that the PAPR of our proposed new scheme is less than the OFDM systems using the frequency domain overlay sequences. Moreover, according to our PAPR analysis, a new PAPR reduction technique via the selective watermark insertion is also designed in this paper.