Physical-layer information hiding technique for cognitive radio communications in cooperative relaying systems

This study presents a novel idea for information hiding at the physical layer level in order to securely transmit confidential cognitive radio data in cooperative relaying systems. Considering a cognitive radio network in which the secondary user cooperates with the primary system in relaying its data, in the proposed model, confidential cognitive information is hidden into the primary signal as a low-power noise at a symbol level such that it would be invisible by malicious users. The new hiding algorithm can be utilised along with any standard relaying scheme as long as the primary information signal is used as the cover data without significant degradation of the primary system performance. In the presence of cognitive data hiding, both the frame error rate and throughput performance of the primary and secondary systems are derived analytically for well-known relaying schemes such as fixed and incremental relaying protocols, when a selection-combining rule is utilised at the primary receiver for symbol detection. Using simulation results the correctness of the proposed theoretical analysis is verified. Moreover, using numerical results the existing tradeoff between the hiding cognitive capacity of the proposed model and the performance degradation of the primary system is highlighted.