In the future, the aeronautics will rely heavily on Global Navigation Satellite Systems (GNSS) such as GPS and Galileo for navigation. However, the GNSS signals are typically quite weak and therefore might be subjected to intentional or unintentional interference; additionally, space weather might have a significant impact on the intermittent performance of the GNSS services. Consequently, a backup solution has to be available to overcome the temporarily interruption of service. Recently, German Aerospace Center (DLR) in Oberpfaffenhofen proposed an Alternative Positioning, Navigation, and Timing (APNT) solution to backup GNSS  services during outages by integrating the navigational functionality into the future L-band Digital Aeronautical Communication System (LDACS) type 1. In the proposed navigational system, called  LDACS-NAV, multiple ground stations transmit time-synchronously signals to the aircraft. The aircraft can then calculate its position based on the range measurements from at least four ground stations, just like in GNSS.
The main goal of this thesis is to investigate how classical GPS tracking loops can be used to calculate the propagation delay based on the LDACS1 signals. In this thesis, the theoretical basis for the phase locked loop and delay locked  loops is reviewed, followed by an explanation of their operation in GPS receivers. Their application to ranging with LDACS signals is considered afterwards. In addition to implementing tracking loops for LDACS1 using MATLAB, further processing of the data collected in a recent flight measurement campaign is discussed. The estimated aircraft range is then compared to the one computed based on a GPS data, which served as a ground truth. The obtained results indicate that the estimated ranges are less than 50m away, with RMSE estimation error being in the range of  16m. The obtained results suggest that LDACS1 is a viable APNT solution.