A game-theoretic and stochastic survivability mechanism against induced attacks in Cognitive Radio Networks.

Cognitive Radio Networks (CRNs) are envisioned to provide a solution to the scarcity of the available frequency spectrum. It allows unlicensed secondary users (SUs) to use spectrum bands that are not occupied by licensed primary users (PUs) in an opportunistic manner. This dynamic manner of spectrum access gives rise to vulnerabilities that are unique to CRNs. In the battle over the available spectrum, SUs do not have any means of identifying whether disruption sensed on a band is intentional or unintentional. This problem is further intensified in the case of heterogeneous spectrum, where different bands provide different utilities. A smart malicious agent can use this vulnerability to temporarily disrupt transmissions on certain bands and induce their unavailability on SUs. The motivation for such disruption-induced attacks can be either monopolism, i.e. to capture as much spectrum as possible and make other SUs starve, or denial of service by intentional disruption of other SUs’ communications. This paper proposes an adaptive strategy for robust dynamic spectrum access in the event of induced attacks. Assuming rational players, and considering the notion of channel utility, the optimal strategy is established by modeling such scenarios as zero-sum games that lead to Nash equilibrium. Thereafter, the case of non-stationary channel utilities is investigated, where utilities are subject to abrupt changes due to fluctuations in channel characteristics, as well as arrival and departure of PUs. Through concurrent estimation, learning, and optimal play, it is shown that the proposed mechanism performs robustly even in such dynamic environments. Comparison of the proposed mechanism to other reasonable benchmark strategies in simulation confirms that this mechanism significantly enhances the performance of CRNs.