Secure inter-cluster communications with cooperative jamming against social outcasts

The concept of device-to-device (D2D) communications has recently attracted broad research and development interests owing to its simplicity and promise to improve spectrum and energy efficiency within existing cellular infrastructure. Because of their less sophisticated control plane, D2D user equipments (DUEs) themselves are not powerful enough against security breaches. This work investigates ways for D2D users to form clusters to shun social outcasts. We form reliable cooperative clusters by considering physical positions of candidate DUEs and by exploiting their social relationship to improve secrecy rate. Our cluster-assisted relay and jammer selection optimization scheme has the dual objective of maximizing the DUE secrecy rate under power constraint and satisfying the requisite signal-to-interference-plus-noise ratio (SINR) need of co-channel cellular user equipments (CUEs). To solve the non-convex optimization problem, we propose a generalized fractional programming (GFP) method by leveraging the Dinkelbach-type algorithm. We also study the impact of social trust and channel estimation error of these mobile nodes to demonstrate the robustness and reliability of the proposed approach. Numerical results show that the proposed scheme can achieve good performance through the underlying D2D cooperation.