• Evaluation of CMA+AMA Equalization for SOQPSK Modulation in Aeronautical Telemetry

      Cole-Rhodes, Arlene; Moazzami, Farzad; KoneDossongui, Serge; Opasina, Oladotun; Umuolo, Henry; Betelle, Habtamu; Thang, Solomon; Shrestha, Robin; Morgan State University (International Foundation for Telemetering, 2013-10)
      Multipath interference continues to be the dominant cause of telemetry link outages in low-elevation angle reception scenarios. The most reliable and universally applicable solution to this problem is in the form of equalization. Previous work in this area has considered the Constant modulus algorithm (CMA) equalizer operating in a blind adaptive mode. To the extent that knowledge of the multipath channel improves the performance of CMA and related equalizers and permits the use of other equalization techniques, data aided equalizers are of interest. Channel knowledge is obtained by comparing the received samples with the samples corresponding to a known bit pattern (called a pilot block) periodically inserted in the telemetry data stream. The main objective of this research is to evaluate the performance of a modified CMA equalization algorithm, which has the property of automatically resolving the phase of the QPSK modulated symbol, and to determine its suitability for use with SOQPSK-TG by taking into account the capability of exploiting the presence of a periodically inserted pilot block. As an initial effort in that direction, this paper provides simulation results of the error performance of the blind linear combination of CMA and alphabet matched algorithm (AMA) equalizer as compared to that of pilot assisted equalization with SOQPSK modulation over aeronautical channel.
    • Variable Rate OFDM Performance on Aeronautical Channels

      Moazzami, Farzad; Cole-Rhodes, Arlene; Dean, Richard; Elrais, Mostafa; Mengiste, Betelhem; Guatam, Bibek; Damiba, Eugene; Morgan State University (International Foundation for Telemetering, 2013-10)
      This paper shows the design and testing of a test bed at Morgan State University as part of the development of a Link Dependent Adaptive Radio (LDAR). It shows the integration of variable rate QAM/OFDM modulation and a variable rate Punctured Convolutional Coder. It also shows a dynamic aeronautical channel simulator developed to capture the dynamics of these channels. Performance results are show for combinations of modulation, coding and channel variations that provide motivation for the potential of the LDAR system.