Air-to-Ground Directional Channel Sounder With Drone and 64-antenna Dual-polarized Cylindrical Array

Abstract

Unmanned Aerial Vehicles (UAVs), popularly called drones, are an important part of future wireless communications, either as user equipment that needs communication with a ground station, or as base station in a 3D network. For both the analysis of the "useful" links, and for investigation of possible interference to other ground-based nodes, an understanding of the air-to-ground channel is required. Since ground-based nodes often are equipped with antenna arrays, the channel investigations need to account for it. This study presents a massive MIMO-based air-to-ground channel sounder we have recently developed in our lab, which can perform measurements for the aforementioned requirements. After outlining the principle and functionality of the sounder, we present sample measurements that demonstrate the capabilities, and give first insights into airto-ground massive MIMO channels in an urban environment. Our results provide a platform for future investigations and possible enhancements of massive MIMO systems.

Channel Knowledge Map Construction Based on a UAV-Assisted Channel Measurement System

“…At present, many approaches have been adopted, For example, the noise threshold in [38] was 25 dB lower than the CIR's strongest path power. In [39], it was 20 dB higher than the mean power of the noise level. In [40], it was 20% of the CIR's strongest path power.…”

“…We use the CIR obtained from the actual measurement for comparison and verification. Figure 4 shows that the adaptive noise threshold generated by the ML-CFRA method at P CFAR = 10 −0.42 , W = 36 and N G = 2 is compared with the constant noise threshold in [38,39]. It can be seen that the use of a constant noise threshold may lead to some multipaths with low power not being missed, resulting in measurement errors.…”

Fundamentals of Wobbling and Hardware Impairments-Aware Air-to-Ground Channel Model

“…Following [6], the authors in [25] studied the Doppler effect at millimeter-wave (mmWave) frequencies for an air-to-ground channel under random UAV wobbling. Apart from analytical results, measurement campaigns have also reported the impact of wobbling as an important source of error in establishing a strong connection in aerial wireless networks [26], [27]. In particular, in [26], the authors used a channel sounder to investigate an air-to-ground wireless link, from which they observed that the variations of the received power from a completely static UAV are much less than that of a hovering UAV.…”

“…Apart from analytical results, measurement campaigns have also reported the impact of wobbling as an important source of error in establishing a strong connection in aerial wireless networks [26], [27]. In particular, in [26], the authors used a channel sounder to investigate an air-to-ground wireless link, from which they observed that the variations of the received power from a completely static UAV are much less than that of a hovering UAV. These studies highlight the importance of considering UAV wobbling in aerial wireless communications.…”