  Resource allocation is conceived for cell-free (CF) massive multi-input
multi-output (MIMO)-aided ultra-reliable and low latency communication (URLLC)
systems. Specifically, to support multiple devices with limited pilot overhead,
pilot reuse among the users is considered, where we formulate a joint pilot
length and pilot allocation strategy for maximizing the number of devices
admitted. Then, the pilot power and transmit power are jointly optimized while
simultaneously satisfying the devices' decoding error probability, latency, and
data rate requirements. Firstly, we derive the lower bounds (LBs) of ergodic
data rate under finite channel blocklength (FCBL). Then, we propose a novel
pilot assignment algorithm for maximizing the number of devices admitted. Based
on the pilot allocation pattern advocated, the weighted sum rate (WSR) is
maximized by jointly optimizing the pilot power and payload power. To tackle
the resultant NP-hard problem, the original optimization problem is first
simplified by sophisticated mathematical transformations, and then
approximations are found for transforming the original problems into a series
of subproblems in geometric programming (GP) forms that can be readily solved.
Simulation results demonstrate that the proposed pilot allocation strategy is
capable of significantly increasing the number of admitted devices and the
proposed power allocation achieves substantial WSR performance gain.
