Power Control in Cell-Free Massive MIMO Networks for UAVs URLLC under the Finite Blocklength Regime

In this paper, we concentrate on the employment of a user-centric (UC) cell-free massive MIMO (CFmMIMO) network for providing ultra reliable low latency communication (URLLC) when traditional ground users (GUs) coexists with unmanned aerial vehicles (UAVs). We study power control in both the downlink and the uplink of such a scenario when partial zero-forcing (PZF) transmit/receive beamforming and maximum ratio transmission/combining are utilized. We consider optimization problems where the objective is either to maximize the total users' sum URLLC rate or to maximize the minimum user's URLLC rate. The considered URLLC rate function is both complicated and nonconvex rendering the considered optimization problems nonconvex. Thus, we present two approximations for the URLLC rate function and resort to successive convex optimization (SCO) to tackle the considered optimization problems. Particularly, we present SCO with iterative concave lower bound approximation (SCO-ICBA) and SCO with iterative interference approximation (SCO-IIA). We provide extensive simulations to evaluate SCO-ICBA and SCO-IIA and compare UC CFmMIMO deployment with traditional colocated massive MIMO (COmMIMO) systems.