Multi-Frequency Band Physical-Layer Authentication in Indoor Environment

In this paper, we propose a physical-layer authentication (PLA) scheme based on wireless channel responses of multiple frequency bands. Channel-based PLA has been regarded as a desirable scheme as it simplifies the authentication process by comparing received and previously acquired channel state information (CSI). However, it may fail authentication due to potential disagreements in CSI among legitimate users. Moreover, in an indoor environment, spatial correlation occasionally arises between legitimate and illegitimate channels, which can degrade the authentication reliability. To mitigate undesired CSI disagreements and spatial correlations, we propose a joint utilization of channel responses in multiple frequency bands. As spatial correlation is unlikely to arise simultaneously in different frequency bands, any correlation with illegitimate channels in one band can be compensated by the other band, providing reliable authentication even in indoor environments. Similarly, any disagreement among legitimate channels in one band can be compensated by the other band that has sufficient channel coherence time. To demonstrate the performance of our proposed scheme, we constructed a test-bed based on universal software radio peripherals. The experimental analysis shows that the proposed PLA scheme can significantly improve the authentication performance as much as orders of error reduction in failures by doubling the frequency bands in channel-based PLA.