I. Introduction
Unmanned aerial vehicles (UAVs) are becoming a mature technology employed in many fields, such as aerial inspection, surveillance, delivery, and ambient awareness [1], [2]. One reason for the high research interest in the field of UAVs is their potential to autonomously navigate indoor or outdoor following a trajectory while avoiding obstacles with low latency [3]. Performing this task includes several challenges, such as online perception, control, trajectory optimization, and localization [4]. The small form-factor category represents an even more promising class of UAVs. The UAVs in this class (i.e., nano-UAVs) measure a few centimeters in size and weigh a few tens of grams [5]. They are considered the ideal candidates for navigating in very narrow indoor areas for monitoring and inspection purposes [6].