The use of coded communications to overcome ionospheric scintillation fading

In an effort to improve UHF satellite communications during the times it is affected by ionospheric scintillation fading, a simulation program was undertaken to investigate coding and interleaving. By making use of the times when the UHF signal is unfaded, it appears that forward error correcting coding can improve message readability. Interleaving of data bits is necessary to convert the long bursts of errors into a somewhat random error pattern which can be corrected by the coding. One-half rate binary feedback coding, one-half rate Viterbi coding and one-third rate Viterbi coding was tried. Various interleaving dimensions were also investigated. A UHF SATCOM channel with fading was simulated using actual scintillation fade data previously collected. The various types of coding/interleaving were played through the channel and the performance of each of these combinations was compared with the uncoded message. The results showed that an improvement in message readability can be achieved with coding/interleaving.