A secure Multi-User Selection Scheme for Internet of Things
This thesis presents a multiuser downlink secure transmission scheme for Internet of Things (IoT) in the presence of multiple eavesdroppers. The scheme adopts transmit antenna selection (TAS) at the base station (BS), selection combining (SC) over the legitimate nodes and cooperative jamming at the jamming node. Depending on whether the jammer node has the channel state information (CSI) of both the main and wiretap channels, it explores the zero-forcing beamforming (ZFB) scheme to confound the eavesdropper while avoiding interrupting the legitimate nodes. Subsequently, a new hybrid secure transmission scheme is proposed, denoted as TAS-SC-ZFB, for IoT networks . We derive, for both colluding (COL) and non-colluding (NCOL) eavesdropping cases, an exact closed form expressions for the secrecy outage probability, and asymptotic secrecy outage probability closed-form expressions obtained at the high signal-to-noise ratio (SNR) regime. Power allocation problem is formulated and solved for the system analyzed. We also considered the worst case scenario when eavesdroppers are colluding and derived expressions for ergordic secrecy rate (ESR) while assuming partial channel state information (CSI). Using these closed-form expressions, the optimal power allocation factor between the BS and jammer is determined to minimize the secrecy outage probability, while the optimal secrecy rate is decided to maximize the effective secrecy throughput for this scheme. Finally, numerical results are obtained to justify the derived expressions and show the impact of the major system parameters on the network's secrecy performance. Lastly, the conclusion and future recommendations are provided to assist in the succeeding research prospects.