  Concerning ultra-reliable low-latency communication (URLLC) for the downlink
operating in the frequency-division multiple-access with random channel
assignment, a lightweight power allocation approach is proposed to maximize the
number of URLLC users subject to transmit-power and individual user-reliability
constraints. Provided perfect channel-state-information at the transmitter
(CSIT), the proposed approach is proven to ensure maximized URLLC users.
Assuming imperfect CSIT, the proposed approach still aims to maximize the URLLC
users without compromising the individual user reliability by using a
pessimistic evaluation of the channel gain. It is demonstrated, through
numerical results, that the proposed approach can significantly improve the
user capacity and the transmit-power efficiency in Rayleigh fading channels.
With imperfect CSIT, the proposed approach can still provide remarkable user
capacity at limited cost of transmit-power efficiency.

Signal Processing