History based forward and feedback mechanism in cooperative spectrum sensing including malicious users in cognitive radio network.

In cognitive radio communication, spectrum sensing plays a vital role in sensing the existence of the primary user (PU). The sensing performance is badly affected by fading and shadowing in case of single secondary user(SU). To overcome this issue, cooperative spectrum sensing (CSS) is proposed. Although the reliability of the system is improved with cooperation but existence of malicious user (MU) in the CSS deteriorates the performance. In this work, we consider the Kullback-Leibler (KL) divergence method for minimizing spectrum sensing data falsification (SSDF) attack. In the proposed CSS scheme, each SU reports the fusion center(FC) about the availability of PU and also keeps the same evidence in its local database. Based on the KL divergence value, if the FC acknowledges the user as normal, then the user will send unified energy information to the FC based on its current and previous sensed results. This method keeps the probability of detection high and energy optimum, thus providing an improvement in performance of the system. Simulation results show that the proposed KL divergence method has performed better than the existing equal gain combination (EGC), maximum gain combination (MGC) and simple KL divergence schemes in the presence of MUs.

Plasma electrochemistry: voltammetry in a flame plasma electrolyte.

In this paper we present detailed dynamic electrochemical measurements in a flame plasma electrolyte in the presence of tungsten oxide salts. Defined reproducible redox processes are measured using conventional cyclic voltammetry in an operational potential window between 1 and -9 V. This wide potential window is possible due to the absence of solvent and its associated limits due to solvent electrolysis at high over potentials. The measurements were enabled through the development of a new reference electrode, composed of yttria stabilised zirconia (YSZ) which maintains a stable potential at 1100 K. In this paper we focus on developing a phenomenological understanding of electron transfer at the solid-gas interface, using cyclic voltammetry. The effect of working electrode surface area and material, as well as potential scan rate on the voltammetric redox features is presented. We discuss the physical origin of the observed Faradaic current peaks measured in a flame plasma electrolyte, and propose a simple model to describe the redox processes occurring. We conclude that redox processes at the solid-gas interface are actually similar to the analogous processes at the solid-liquid interface described by conventional electrochemical theory; the departures are mainly due to the mass transport processes that dominate in the gas phase. We associate migration effects with the total absence of any oxidation processes.

Dynamic electrochemistry in flame plasma electrolyte.

Chemistry in flames: Dynamic electrochemistry in the gas phase is described by considering the ionized medium of a flame as an electrolyte (see picture). This study opens up the possibility of accessing redox reactions that are outside the potential limits set by the solvent in conventional liquid-phase electrochemistry.