  This paper considers the resource allocation algorithm design for downlink
multiple-input single-output (MISO) orthogonal frequency division multiple
access (OFDMA) ultra-reliable low latency communication (URLLC) systems. To
meet the stringent delay requirements of URLLC, short packet transmission is
adopted and taken into account for resource allocation algorithm design. The
resource allocation is optimized for maximization of the weighted system sum
throughput subject to quality-of-service (QoS) constraints regarding the URLLC
users' number of transmitted bits, packet error probability, and delay. Despite
the non-convexity of the resulting optimization problem, the optimal solution
is found via monotonic optimization. The corresponding optimal resource
allocation policy can serve as a performance upper bound for sub-optimal
low-complexity solutions. We develop such a low-complexity resource allocation
algorithm to strike a balance between performance and complexity. Our
simulation results reveal the importance of using multiple antennas for
reducing the latency and improving the reliability of URLLC systems. Moreover,
the proposed sub-optimal algorithm is shown to closely approach the performance
of the proposed optimal algorithm and outperforms two baseline schemes by a
considerable margin, especially when the users have heterogeneous delay
requirements. Finally, conventional resource allocation designs based on
Shannon's capacity formula are shown to be not applicable in MISO OFDMA-URLLC
systems as they may violate the users' delay constraints.
