Key Observations from Altitude-Dependent Sub-6 GHz Spectrum Measurements at AERPAW

In this paper, we briefly overview the NSF AERPAW platform as an aerial spectrum monitoring testbed and discuss representative results from the platform. In particular, we provide a series of observations on the dependence of spectrum occupancy on altitude, environment, uplink or downlink transmission, and technology. We elaborate on how spectrum occupancy models can help to develop more effective spectrum reuse techniques. Based on the results discussed, we end the paper by providing several recommendations on future research directions and the implementation of the national spectrum strategy.