The problem of communicating binary information from ground to aircraft via L -band aeronautical satellite channels is addressed, with particular attention given to the effect of and means of combating diffuse-scattered multipath interference. Differential phase-shift keying (DPSK) is considered throughout. Test results of a recent flight-test program are summarized and compared to theory for uncoded DPSK. We then discuss and evaluate the use of diffuse convolutional codes in conjunction with threshold decoding to improve error probability on the fading channel. Simulation has shown that a power saving of 8 dB may be gained at 10 -5 error rate for typical channel conditions with very little complexity.

Results of a flight test program involving a KC-135 jet airplane, the synchronous ATS-5L-band satellite, and a ground station are presented. Tests included over-ocean multipath measurements and one-way tone ranging within the 1545-1655 MHz frequency band. Amplitude characteristics, polarization, power spectral density, and selective fading properties were measured for sea-reflected and composite s...