Information-Freshness-Aware Wireless Multiuser Uplink Physical-Layer Security Communication

In this article, we focus on a wireless multiuser uplink network consisting of a single antenna access point (AP) and multiple single antenna users, in which each user transmits time-sensitive confidential message to the AP in a time-division multiple access (TDMA) manner. When a user is scheduled to transmit, the other users will be regarded as potential eavesdroppers. In practical Internet of Things (IoT) applications, different users may have different requirements for throughput, and the timeliness of information needs to be guaranteed. In order to effectively adapt to these heterogeneous application requirements, the average weighted sum Age of Information (AoI) minimization problem is formulated under the premise of satisfying the minimum sampling rate requirement, power allocation constraint, and user scheduling constraint. In order to solve this problem, we first propose two stationary randomized scheduling policies, which are modeled as D/Geom/1 and Geom/Geom/1 queueing systems, respectively, and design two algorithms to find the optimal sampling period of D/Geom/1 system, the sampling probability of Geom/Geom/1 system, the power ratio allocated to confidential information, and the user scheduling probability. Second, an AoI-aware adaptive secure transmission scheme (AASTS) is proposed under Lyapunov optimization framework by transforming the original time-average weighted sum AoI minimization problem into a real-time optimization problem related to data queue state and AoI evolution of every time slot. Numerical results show that the proposed AASTS scheme can achieve better average AoI performance, and the D/Geom/1 system is superior to the Geom/Geom/1 one.