QoS-Aware EnhancedSecurity EnhancedSecurity EnhancedSecurity for TDMA Transmissions from Buffered Source Nodes

This paper proposes a cross-layer design to secure a set of buffered legitimate source nodes wishing to communic ate with a common destination node using a time-division multipleaccess scheme. The users’ assignment probabilities to the t ime slots are optimized to satisfy a certain quality-of-service (QoS) requirement for all the legitimate source nodes. To further improve the system security, we propose beamforming-based cooperative jamming schemes subject to the availability ofthe channel state information (CSI) at the legitimate nodes. Wederive closed-form expressions for the instantaneous secrecy rat e for each scheme as well as the secrecy outage probability. Moreo ver, we derive the secrecy stable-throughput and delay-require ment regions. In our proposed scheme, if a node is not selected for data transmission, it is a cooperative jamming node. We impose an average transmit power constraint on each source node. We investigate the cases where a global CSI is assumed at the legitimate nodes and where there is no eavesdropper’s CSI. The case where there is no CSI at the jamming nodes is also investigated and a new scheme is proposed. Our proposed jamming schemes achieve significant increases in the secure throughput over existing schemes from the literature and over the no-jamming scheme.