DME/DME navigation using a single low-cost SDR and sequential operation

Federal Aviation Administration is initiating an Alternative Position, Navigation, and Timing (APNT) program to insure continuous services in the event of GNSS failure. One of the promising solutions is an Optimized Distance Measuring Equipment (DME) Network based on DME/DME navigation. In comparison to other proposed APNT architectures, such as DME pseudolite network and passive Wide-Area Multilateration, airline operators find DME/DME more attractive for backup, as this solution requires no change to avionics used by commercial aircraft. This paper presents the implementation of the DME/DME system on the low-cost, Software Defined Radio (SDR) Nutaq ZeptoSDR platform. The SDR technology was chosen for its flexibility and reconfiguration. In fact, the success of implementing the DME avionic in a SDR platform will provide opportunities to implement other technologies. With such a versatile platform many problems can be avoided in an aircraft like the excessive wiring. To enable DME/DME in a single radio SDR, a new concept: “Sequential DME/DME” is introduced. This paper describes the principle of operation of the system and its implementation. To evaluate the Sequential DME/DME in a laboratory environment, a test bench platform is developed using avionics certification equipment. In lab tests using this platform are conducted to evaluate the system performances and results are presented. The accuracy of the system is studied by examining distance and position measurement precision.