Lightweight and Fast Physical-Layer Key Generation in FDD Systems using Random Forest

Physical-layer Secure Key Generation (SKG) in wireless communication provides high-level security originating from channel uniqueness. However, the carrier frequency difference in Frequency Division Duplexing (FDD) systems degrades the channel reciprocity, compromising the feasibility of SKG and subsequently the Key Generation Rate (KGR). We propose a lightweight and fast SKG scheme with enhanced KGR in FDD systems, using the Random Forest (RF) algorithm in conjunction with a Multi-to-Single Mapping (M2SM) strategy. Besides, the Moving Average (MA) and subtraction algorithms further enhance the SKG performances under noisy and frequency-selective fading FDD channels. Experimental results revealed an error-free KGR of 57.71 Kbps, with superior randomness, showing the practicability of high-speed and robust SKG in FDD systems. Moreover, the proposed scheme has low complexity, high flexibility, and information-theoretic security.