Cooperative Secure Transmission by Exploiting Social Ties in Random Networks

Social awareness and social ties are becoming increasingly popular with emerging mobile and handheld devices. Social trust degree describing the strength of the social ties has drawn lots of research interests in many fields in wireless communications, such as resource sharing, cooperative communication, and so on. In this paper, we propose a social ties based hybrid cooperative beamforming and jamming scheme to secure wireless transmissions under a stochastic geometry framework, where the friendly nodes are categorized into relays and jammers according to their locations and social trust degrees with the source node. Connection outage probability (COP) and secrecy outage probability (SOP) of such a scheme in a random network have been analyzed. To facilitate a more convenient performance evaluation, we propose a double Gamma ratio approach through the Gamma approximation method. Based on this, the COP and SOP are tractably obtained in closed-forms. We further consider the SOP in the presence of Poisson point process distributed eavesdroppers and derive an upper bound. The simulation results verify our theoretical findings, and validate that the social trust degree has dramatic influences on the security performance in the networks.