Optimal Age of Information and Throughput Scheduling in Heterogeneous Traffic Wireless Physical Layer Security Communications

A wireless multi-user uplink heterogeneous network is investigated in this paper, which comprises an access point and two distinct user groups including throughput-oriented users and age of information (AoI)-oriented users, in which throughput-oriented users prioritize achieving as high throughput as possible, while AoI-oriented users emphasize timely transmission of information. It is assumed that the transmitted information needs to be kept strictly confidential to unintended users, and the time-division multiple access (TDMA) approach is adopted to transmit confidential information of each user. For such a network, all users who are not scheduled for transmission will be treated as potential eavesdroppers. The objective of our work is to maximize the average achievable secrecy rate of throughput-oriented users while minimizing the average AoI of AoI-oriented users subject to the data queue causality and stability constraints, the sampling rate requirements of AoI-oriented users, the time-averaged and peak transmission power constraints, and the user scheduling constraint. We propose using Lyapunov optimization to convert the original time-averaged optimization problem into a sequence of real-time ones associated with both queue sizes and AoI involved in the current time slot. On this basis, an adaptive heterogeneous traffic security transmission (AHTST) strategy is proposed to determine the optimal strategies for the flow control of throughput-oriented users, the sampling rate control of AoI-oriented users, the power allocation, as well as the user scheduling. Numerical results demonstrate that the AHTST strategy surpasses the considered benchmark schemes in both achievable average secrecy rate and average AoI.