• DOPPLER ESTIMATION AND COMPENSATION FOR LTE-BASED AERONAUTICAL MOBILE TELEMETRY

      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.
    • RF Planning for 3D coverage in Cellular LTE Range Telemetry

      Harasty, Dan; Kogiantis, Achilles; Maung, Nan; Rege, Kiran; Triolo, Anthony; Perspecta Labs (International Foundation for Telemetering, 2018-11)
      Initial analysis and lab experiments have provided positive confirmation of the viability of 4G LTE Cellular Technology for Aeronautical mobile telemetry. COTS LTE equipment is deployed for the test range frequency bands. The high speeds of test articles (TAs) can be addressed with a UE add-on applique’ customized to compensate for the Doppler shifts. The applique has worked effectively with the LTE physical layer. To achieve spectrum efficiency, a multi-cell network is planned. Mobility is managed with native LTE handovers. To address extreme Doppler cases, additional support is provided to mobility management via a central entity that estimates the TA’s trajectory and issues handover commands. Within this framework, we present aspects of an RF planning study that characterizes the dependence of coverage on such design parameters as base station density, antenna orientation, and altitude of the user device. We also quantify the Doppler shifts that can result under the standard strategy of connecting the user device to the strongest cell, and show how, with an alternative, threshold-based strategy, one can achieve a substantial reduction in Doppler shifts at the expense of a loss in user rates.