This article presents a set of nondestructive test methodologies designed to evaluate and compare performance of the communication links used for control and telemetry of small unmanned aircraft systems (sUAS) (drones) that are operating indoors and in subterranean environments. Such a set of standardized test methodologies does not yet exist. Indoor and subterranean operation requires sUAS to operate without global positioning system and often in a spatially constrained non-line-of-sight (NLOS) communication environment. Operating in constrained indoor environments puts additional constraints on the communication links and requires a set of tests to allow evaluation and comparison of different units in typical scenarios that will be encountered. Tests to measure and compare communication link performance and ability to pilot in tunnels and office type buildings with doors, walls, and other obstructions, as well as stairwells are described. The test methods consist of measuring and comparing the NLOS radio range between the sUAS and the ground control station or operator control unit (OCU), observing the sUAS behavior with partial or total communication failure. Near the edge of coverage, correlated packet loss can lead to difficulties in piloting. A methodology for evaluating video latency that is critical for remote piloting by camera only is presented. Finally, a test methodology for characterizing the effects of interference and jamming by waveforms such as Wi-Fi often encountered in buildings is described. These test methodologies described here extend standards developed for ground robots to three dimensions. The test methodologies described in this article are part of a multifaceted project that evaluates many essential elements of drone operation indoors. These include communication, navigation, collision tolerance, mapping, trust, and automation. The test methodologies are designed to be reproduced in user facilities.
