Physical Layer Key Generation Scheme for Wideband Large Antenna Array Systems

Abstract

Physical layer security shows growing importance in wireless communication systems because the time division duplexing (TDD) channel reciprocity provides an attractive opportunity for physical layer key generation (PKG). However, PKG method suffers from the challenge of explosively increasing pilot overhead as the number of antennas becomes large. In this paper, we propose a low-overhead joint long-term and short-term PKG scheme for wideband large antenna array systems. To be specific, considering the sparsity of the channel in large antenna array systems, we explore the slow-varying characteristic of the angles and delays of the propagation paths and gener-ate the long-term keys based on these parameters. Then, by applying beamforming, we track the reduced-dimensional fast-varying channel and generate the short-term keys based on the channel tracking results across the whole band. This scheme can effectively generate the keys with low overhead. Numerical results verifies the generated keys are sufficiently long and random.