Identification of Distance Measuring Equipment Interrogations

Distance Measuring Equipment is included into the main list of on-board navigation equipment of civil airplanes. Current performance-based navigation considers DME as a primary sensor for stand-by on-board positioning equipment. During the cycle of range measuring, on-board DME interrogator interacts with a ground-based navigational aids network. Accuracy of range measuring depends on performance and workload of navigational aids network. Navigation signals of Distance Measuring Equipment use Gaussian pulse-pairs form, which does not support signal identification in the ground-based transponder. We propose an algorithm for identification of Distance Measuring Equipment interrogations with a particular air space user. Proposed algorithm is based on navigation signal amplitude detection, clusterization by mean value, and interrogation identification with airspace users located in the operational range of navigational aid based on range criteria. A method of maximal posterior probability is used for interrogation identification with a particular airspace user, which supports recognition with the highest level of probability. Proposed algorithm was integrated into a passive system based on two Software Defined Radios for navigation signal monitoring. Integration of proposed algorithm at the software level of secondary data processing system in the national navigational aids network makes possible to provide user-based service analysis in order to improve overall network performance.