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Post-1980 Facilities Control Concept Study.

Descriptive Note:

Semiannual rept. n0. 1, 1 Jul-31 Dec 72,

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Optimum automatic techniques have been developed to monitor digital TDM link quality and restore and maintain frame synchronization and BCI. The radio baseband eye pattern closure indicates trends in BER on the encrypted link, while errors in the frame synchronization pattern and frame parity accurately determine link quality. Link quality standards developed allow an error rate of 0.005 and 0.000005 to be exceeded no more than 2 of 3 minutes for digitized voice and data. Radio receiver status and BER trends are telemetered to the quality monitor and BCI restoral processor once every 22 ms every 5 ms when the error rate is greater than 0.08 using 400-bs DPSK in the 2000-Hz to 2800-Hz band in the analog voice orderwire. Presence of frame synchronization pattern indicates proper BCI. When the latter is lost and the BER trend is better than 0.08, a three-mode frame synchronization subsystem searches for synchronization in the decrypted bit stream by deleting or addding additional data bits into the bit stream prior to decryption. The cryptographic equipment is resynchronized to reestablish BCI if the frame resynchronization is unsuccessful or if the BER is indicated less than 0.005. A study of the statistics of fades and instantaneous error rates for Rayleigh fading LOS and troposcatter digital ratio links is included with many plots of fade rate, average fade BER durations, and distribution of duration of fade BER burst. Author

Subject Categories:

  • Cybernetics
  • Command, Control and Communications Systems

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