Intelligent Jamming Strategies for Secure Spectrum Sharing Systems

Abstract

This paper investigates the secrecy performance of a spectrum sharing network, where <inline-formula> <tex-math notation="LaTeX">${N}$ </tex-math></inline-formula> legitimate source-destination pairs orderly access the shared spectrum for communication, while an eavesdropper (E) attempts to tap the legitimate information transmission. To improve the physical layer security, we propose two jamming strategies that can intelligently switch between jamming and non-jamming, namely, suboptimal jammer selection (SJS) scheme and optimal jammer selection (OJS) scheme. Specifically, when a user pair is assigned to access the shared spectrum, another source is chosen as a friendly jammer in order to create intentional interference at E. For the purpose of comparison, we present the non-jammer selection (NJS) scheme as a benchmark. Analytical closed-form secrecy outage probability expressions of NJS, SJS and OJS schemes are derived over Nakagami-<inline-formula> <tex-math notation="LaTeX">${m}$ </tex-math></inline-formula> fading channels. We further present an asymptotic secrecy outage probability analysis to evaluate the secrecy diversity gain performance of NJS, SJS and OJS schemes. Numerical results show that the secrecy outage probability performance of OJS scheme is better than SJS and NJS schemes in the low average channel power gain <inline-formula> <tex-math notation="LaTeX">${\mathop \Omega \nolimits _{D} }$ </tex-math></inline-formula> region. Furthermore, the secrecy outage probabilities of NJS as well as SJS and OJS schemes converge to each other with the increase of <inline-formula> <tex-math notation="LaTeX">${\mathop \Omega \nolimits _{D} }$ </tex-math></inline-formula>, due to the fact that the OJS and SJS scheme will switch to NJS scheme when <inline-formula> <tex-math notation="LaTeX">${\mathop \Omega \nolimits _{D} }$ </tex-math></inline-formula> tends to infinity.