Highly Efficient FDD Secret Key Generation using ESPRIT and Jump Removal on Phase Differences

In this study, a highly efficient simple approach to generate secret keys for Frequency-Division Duplexing (FDD) systems is proposed. We use phase differences between neighboring antennas in a linear array to construct the channel profile and the ESPRIT (Estimation of Signal Parameters using Rotational Invariance Techniques) algorithm for estimating the direction of arrival (DOA). In order to increase the channel reciprocity, we approximate the frequency behavior of the phase differences by polynomial curve-fitting. Rather than using unwrapping to prevent jumps, we propose two jump-removing and outlier-correction algorithms which can bring the efficiency to 100 %. Numerical results verify that the measurements have a minimum variance after using both proposed pre-processing algorithms. Furthermore, the corrected version of measurements has perfect efficiency and better performance on curve-fitting results and key disagreement rate.