In this letter, a recently conducted measurement campaign in two suburban scenarios for investigating the low-height air-to-ground channels is presented. A universal-software-radio-peripheral-based channel sounder on-board an unmanned aerial vehicle (UAV) was exploited to record the real-time downlink signals of the live Long Term Evolution networks. Several horizontal flights at different heights were conducted in the measurement campaign. Channel impulse responses (CIRs) of links from the UAV to different live cells were extracted by exploiting the cell-specific reference signals received in the downlink data. By using the empirical CIRs, a maximization likelihood estimator is derived based on the space-alternating generalized expectation-maximization principle to obtain the signal power for individual channels between multiple base stations and the UAV. Interference, number of detected cells, handover rate, etc., are studied, which provide insights to understand interference for low-height air-to-ground channels.
- Air-to-ground (A2G)
- Long Term Evolution (LTE)
- Propagation channel
- Unmanned aerial vehicle (UAV)