PHY-layer authentication using hierarchical modulation and duobinary signaling

In a cognitive radio network, the non-conforming behavior of rogue transmitters is a major threat to opportunistic spectrum access. One approach for facilitating spectrum enforcement and security is to require every transmitter to embed a uniquely-identifiable authentication signal in its waveform at the PHY-layer. In existing PHY-layer authentication schemes, known as blind signal superposition, the authentication/identification signal is added to the message signal as noise, which leads to a tradeoff between the message signal´s signal-to-noise (SNR) and the authentication signal´s SNR under the assumption of constant average transmitted power. This implies that one cannot improve the former without scarifying the latter, and vice versa. In this paper, we propose a novel PHY-layer authentication scheme called hierarchically modulated duobinary signaling for authentication (HM-DSA). HM-DSA introduces some controlled amount of inter-symbol interference (ISI) into the message signal. The redundancy induced by the addition of the controlled ISI is utilized to embed the authentication signal. Our scheme, HM-DSA, relaxes the constraint on the aforementioned tradeoff and improves the error performance of the message signal as compared to the prior art.