Permutation-based short-packet transmissions improve secure URLLCs in the internet of things

As a promising candidate for ultrareliable and low-latency communications, the recent permutation-based transmission concept substantially improves the resource utilization efficiency in the Internet of Things (IoT). In this context, the Age of Information (AoI) experienced in permutation-based short-packet transmissions is characterized in a wiretap channel, where eavesdroppers are wiretapping the status updates delivered over the legitimate link. The AoI of the legitimate link and the secrecy margin of the wiretap channel are formulated in closed forms within the regime of finite-blocklength information theory to quantify the data freshness and security of status updates in the IoT. The optimal packet structure to be delivered over the network interface is found by solving the optimization problems of minimizing the legitimate link's AoI and maximizing the secrecy margin. Illustrative numerical results are provided for our permutation-based transmission to quantify its performance gains over the conventional encapsulation, specifically in short-packet communications.