Physical layer security in massive internet of things: delay and security analysis

Delay and security are both highly concerned in massive internet of things (IoT) which is a promising application scenario in 5G wireless communication system. In this study, the authors develop an integrated framework to study delay performance and secrecy performance in massive IoT. First, stochastic geometry and queuing theory are applied to model the spatially location of IoT devices and the temporal arrival of packets. To enhance the physical layer security of massive IoT with limited overhead increment at IoT devices, a low-complexity noise injection scheme is applied. Then, the packet delay and packet secrecy outage probability are derived to characterise delay performance and secrecy performance. It is demonstrated that the IoT device intensity and power allocation coefficient arouse a tradeoff between the delay and security. Furthermore, optimal power allocation coefficient that maximises secrecy transmission rate can be derived, which can improve the delay-security tradeoff. The analytical and simulation results show the effects of power allocation coefficient and IoT device intensity on the tradeoff between delay performance and secrecy performance.