A two dimensional quantization algorithm for CIR-based physical layer authentication

Recently, channel impulse response (CIR) based physical layer authentication has been studied to enhance the security of wireless communications. However, the reliability of CIR-based authentication is substantially reduced at low signal-to-noise ratio (SNR) conditions due to the presence of communications noise, channel estimation error and mobility induced channel variation. To this end, we integrate additional multipath delay characteristics into the CIR-based physical layer authentication and propose a two dimensional quantization scheme to tolerate these random errors of CIRs for reduced false alarm rate and more reliable spoofing detection. Instead of directly comparing the estimated CIRs from different transmitters for authentication purpose, we first quantize the CIR estimates in two dimensions (i.e., the amplitude dimension and multipath delay dimension) and then differentiate transmitters based on the quantizer outputs with a binary hypothesis testing. More specifically, the quantization intervals are determined by using a searching algorithm based on a guaranteed miss probability of detection of the presence of spoofing attack. A logarithmic likelihood ratio test (LLRT) is used to evaluate the authentication performance, and a threshold with a constant value is used for the decision-making of authentication under the binary hypothesis testing. To verify the effectiveness of proposed algorithm, an orthogonal frequency division multiplexing (OFDM) system is considered in our simulation.