Fung, Eddie; Johnson, William H.; Kogiantis, Achilles; Rege, Kiran M.; Perspecta Labs (International Foundation for Telemetering, 2018-11)
      High Doppler shifts between base stations and test articles (TAs) pose the biggest problem to Aeronautical mobile telemetry (AMT) implemented on a wireless LTE network. Our solution to this problem includes a Doppler estimator/compensator (DEC) that proactively shifts the LTE uplink (LTE UL) signals transmitted by the TA. We have designed the DEC in the form of an applique’ that can be inserted between the transmit/receive ports of a COTS TA transceiver and its antenna(s). The DEC estimates the Doppler shift using the LTE UL signals transmitted by the TA, which carry a frequency offset that includes the Doppler shift. This not only provides a clean, noise- and fading-free signal for Doppler estimation, but also allows us to do away with the need to know the identity of the base station with which the TA is communicating. In this paper, we provide an architectural description of the DEC and an outline of the algorithms that have been incorporated into it. At present, a laboratory prototype of the DEC has been developed using Universal Software Radio Peripherals (USRPs), coupled with a Linux PC to carry out most of the computations. An FPGA-based implementation is currently under development.