Non-cooperative superposition relaying for multicarrier cognitive networks

In this paper, we consider a broadband cognitive radio network, where the primary and secondary systems employ a multicarrier modulation scheme. The proposed spectrum-sharing scheme is based on additive superposition coding: specifically, the secondary transmitter acts as an amplify-andforward relay, forwarding a linearly weighted combination of the received multicarrier primary signal and its own block of multiple symbols. Such a superposition is performed by the secondary transmitter on the fly, in a single multicarrier symbol of the primary system. Moreover, the proposed scheme does not require cooperation between the primary and secondary systems. An information-theoretic performance analysis of the proposed scheme is developed, whose findings are corroborated by means of numerical Monte Carlo simulations.