Signal Constellations for Physical-Layer Security

Inhalt:
In any transmission scheme, security against an eavesdropper is of importance. Contrary to classical encryption, security directly at the physical layer can be achieved by applying suited coding and modulation schemes. Meanwhile it has been shown that using higher-order constellations in combination with multilevel coding is able to improve the level of security. In this paper, the influence of the constellation, in particular its cardinality and its dimensionality, on the gained security is assessed. Moreover, the effect of signal shaping, i.e., choosing a non-uniform distribution of the signal points, is investigated. Based the channel capacity we present a criterion to optimize the distribution. The theoretical findings are supported by numerical simulations employing punctured LDPC codes.