• AN APPROACH FOR BER DETERMINATION USING LOGGED AERONAUTICAL TELEMETRY DATA

      Tamakuwala, Jimmy B.; Sonar, Souvik; Jena, Avijit; Integrated Test Range, DRDO Chandipur; Defense Research and Development Organization (International Foundation for Telemetering, 2019-10)
      BER is regarded as the link-performance metric in a digital communication system. It is a function of Eb/N0 and is dependent on the modulation scheme used. This relation is often used in prediction of ground telemetry systems performance for a mission configuration. However, there is no objective way of comparing the post flight results, as BER measurement in a flight test is not practically feasible for want of transmitting sufficient reference bit patterns. In this paper, an indirect way of computing BER and, in turn, link Eb/N0 is proposed for a PCM/FM link based on the frame synchronised data logged by the ground telemetry equipment. Using known quantities like bit rate and frame rate, a quantity defined as frame loss rate is computed. Applying the relations between frame loss probability, frame sync pattern and SFID information in the PCM format, an approach for bit error probability is demonstrated based on field data. By using a sliding window over a fixed length of data, BER for the entire flight duration can be determined as a function of flight time with the step size of the length of data window.
    • LESSONS LEARNED DURING THE INTRODUCTION OF NETWORK / IP TELEMETRY IN FLIGHT TEST INSTRUMENTATION FOR HELICOPTERS

      Urli, Renaud; Mertl, Florian; Flight Test Instrumentation, Dept. ETXMI; Airbus Helicopters Deutschland GmbH; Industriestrasse 4 (International Foundation for Telemetering, 2019-10)
      Flight Test Instrumentation (FTI) architectures are moving more and more towards network topologies. For almost every task, current equipment support connection to the FTI system via Ethernet. However, up to now, the telemetry link has kept the legacy PCM technology for most applications. By implementing network / IP radios, the drawbacks of old fashioned PCM-based telemetry links could be eliminated. Furthermore, new use cases have become possible, and the architecture of FTI installations, both on board and on ground, could be simplified. This paper gives some technical background on networked / IP radios and describes the steps taken during the first introduction of this promising technology. The benefits of this system are explained in order to show the potential of that approach. Beside this, important lessons were learned during the introduction of the network / IP telemetry: from software to hardware topics, from topology to human factors aspects. Eventually, the present installation at the FTI facility is described as well as the status of the migration from S-band PCM/FM to IP C-Band.