Experimental Results of Utilizing the 3GPP LTE Positioning Protocol for Providing RTK Reference Data to High-Accuracy UAV Operations

This paper presents experimental results of utilizing the 3GPP standardized RTK Observation State Representation (OSR). The work investigates the 3GPP LTE Positioning Protocol (LPP)'s applicability for enabling reliable and accurate global localization during UAV operations. The experiments are conducted with a UAV connected to a 5G network, utilizing a cellular connection for 1) directly receiving RTCM data via an open-source 3GPP LPP client developed by the authors, and 2) establishing a C2 link to the Ground Control Station. A 24-hour measurement with the UAV remaining at a static position has been conducted. The results indicate a reliable performance with no loss of RTK GNSS fixed solution. Furthermore, two similar static experiments have been conducted with: 1) receiving RTCM data via an NTRIP client connected to an RTK reference network service, indicating no difference in the two approaches' performance when compared, and; 2) with no RTCM data provided, to compare the baseline performance of the UAV's GNSS. The operational reliability, meaning its performance during operational conditions when receiving RTCM data via LPP, has been investigated with UAV flights. The results consist of measurements from 1) the UAV's RTK GNSS to investigate its performance during flight, and; 2) the 5G network to investigate its performance in different altitudes and potentially correlate loss of RTK GNSS fixed solution due to the network connectivity. Seventeen flight experiments have been conducted, resulting in a total flight time of 3 hours and 19 minutes distributed over 32.06 kilometers. No loss of RTK GNSS fixed solution was observed, showing stable operational reliability in the area where the flight tests were conducted.