Protecting processing elements in communications satellites

Fault tolerance features in the first three major subsystems of the satellite up-link resources are described. The critical processing subassemblies are the demultiplexer, demodulators, and forward error-correcting decoders. The extra checking resources needed for fault tolerance also serve as replacements for failed units during reconfiguration. The demultiplexer, an efficient multirate filter bank, containing a fast Fourier transform (FFT) section, is protected by a high rate real number convolutional code, and parity values are computed in parallel at a much reduced rate. The redundancies inherent in the binary convolutional code used to combat transmission noise afford protection for the Viterbi decoders. Selected invariant features of the Viterbi algorithm coupled with the code structure constantly monitor values within the decoder. The demodulators are protected by virtue of their location between two protected units, the demultiplexer and the decoders.<>