Secure and Timely Status Updates in the IoT using Short-Packet Permutation-Based Transmissions

The permutation-based transmission has been recently proposed as an efficient transport-layer design strategy to achieve ultra-reliable and low-latency communications (URLLCs) in the Internet of Things (IoT). In this paper, the age of information (AoI) is exploited as a framework to characterise the performance of short-packet permutation-based transmissions in a wiretap channel, and the concept of secrecy margin is formulated to quantify the data security while guaranteeing the data freshness of status updates. In solving the optimisation problem of secrecy margin maximisation within the regime of finite-blocklength information theory, the optimal packet structure over the network interface is obtained in the IoT using short-packet permutation-based transmission. Illustrative numerical results on the comparisons between the permutation-based transmission and the conventional encapsulation not only substantiate the performance gains achieved by the former, but also provide useful references for its system design for achieving secure URLLCs.