Continuous Physical Layer Authentication Using a Novel Adaptive OFDM System

Traditional authentication techniques for wireless communications are facing great challenges, due to the open radio propagation environment and limited options of transmission techniques. A new continuous physical layer authentication technique with time-varying transmission parameters is investigated to enhance the security of orthogonal frequency division multiplexing (OFDM) system. A preceded cyclic prefix (PCP) sequence, which introduces an additional signaling link to carry the time-varying transmission parameters, is employed in each OFDM symbol for physical layer authentication. The new PCP sequences are generated with the same time and frequency domain characteristics as data-carrying OFDM signals to reduce the interception probability. With the proper recovery of system parameters and interference cancellation, only legitimate users can successfully decode the PCP sequence and obtain necessary parameters to decode OFDM data. In addition, a cross layer design approach, which addresses the dependency among PCP configurations, authentication performance and transmitting performance, is introduced to continuously generate optimal PCPs according to dynamic communication conditions. Numerical simulations confirmed that the system performance, in terms of system robustness, security and stealth, can be significantly improved by using the proposed continuous authentication.