  Ultra-reliable low latency communication (URLLC) is one of three primary use
cases in the fifth-generation (5G) networks, and its research is still in its
infancy due to its stringent and conflicting requirements in terms of extremely
high reliability and low latency. To reduce latency, the channel blocklength
for packet transmission is finite, which incurs transmission rate degradation
and higher decoding error probability. In this case, conventional resource
allocation based on Shannon capacity achieved with infinite blocklength codes
is not optimal. Security is another critical issue in mission-critical internet
of things (IoT) communications, and physical-layer security is a promising
technique that can ensure the confidentiality for wireless communications as no
additional channel uses are needed for the key exchange as in the conventional
upper-layer cryptography method. This paper is the first work to study the
resource allocation for a secure mission-critical IoT communication system with
URLLC. Specifically, we adopt the security capacity formula under finite
blocklength and consider two optimization problems: weighted throughput
maximization problem and total transmit power minimization problem. Each
optimization problem is non-convex and challenging to solve, and we develop
efficient methods to solve each optimization problem. Simulation results
confirm the fast convergence speed of our proposed algorithm and demonstrate
the performance advantages over the existing benchmark algorithms.
