Abstract
Cellular to air communication is critical for the booming aerial package delivery and transportation business. Detecting cellular signals in airborne applications is challenging because it requires receiving and processing waveforms that are subject to significantly more interference than those experienced in terrestrial settings. This paper highlights and tackles the complexity of 4G Long Term Evolution (LTE) signal synchronization in high altitude applications, e.g., cell access onboard an aircraft. Specifically, we design a novel cell detector that operates efficiently under high interference levels found in airborne applications, maintains a constant false alarm rate using an optimized threshold implementation for Zadoff Chu sequences, and monitors multiple towers with different time delays simultaneously. We validate our cell detector through simulation and experimentation. Lastly, the cell detector is used to estimate the interference in live waveforms taken from an aircraft at 2 to 2.5 km altitude and velocities of 200–400 km/h. Our cell detection model can be adapted to support 5G New Radio (NR) synchronization signals as NR deploys aerial support in the future. The threshold implementation to handle correlation spurs can be applied directly to other Zadoff Chu based signals such as random access signals found in both LTE and NR.
Highlights
Cellular signal detection and synchronization for groundbased applications have been thoroughly investigated [1], [2]
EXPERIMENTAL RESULTS We have evaluated the performance of the cell detector by estimating the level of interference in waveforms collected from an aircraft during flight over a suburban and rural area in Frederick County, Maryland, USA, that is served by multiple Long Term Evolution (LTE) towers
We have defined a threshold and correlation to noise ratio (CNR) for our detector based on Zadoff Chu correlation spurs to provide a stable false alarm rate and allow for multiple diverse cell detections
Summary
Cellular signal detection and synchronization for groundbased applications have been thoroughly investigated [1], [2]. Optimized cellular signal detection and synchronization for airborne applications is necessary. With the existing LTE infrastructure, the majority of nonterrestrial research and testing has been conducted with UAVs at altitudes of 30 to 150 meters and velocities of 30 to 50 km/h [11]–[14] At these speeds and low altitudes, many of the challenges in establishing and maintaining synchronization do not manifest fully as compared to those encountered at higher altitudes (e.g. 2 – 2.5 km) and speeds (e.g. 200 – 400 km/h). While some existing studies address airborne access to LTE, they do not attempt to optimize the synchronization process itself for an airborne application and detect multiple synchronization sources. A table of all used acronyms is provided in the Appendix for easy access
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
