On the Reversibility of Randomizers and Derandomizers in Aeronautical Telemetry

Data may be recovered when randomization and derandomization are applied in the reverse order as long as the initial register conditions for both the randomizer and derandomizer are identical. In the (very realistic) case where the initial register contents for the derandomizer are not known, simple procedures for identifying the correct initial conditions are described. The procedures leverage the presence of frame synchronization words in the telemetry data.