Coding and Synchronization Analysis of the NILE UHF Fixed-Frequency Waveform

摘要

The NILE UHF fixed frequency waveform employs an RS (48,30) error control codewith 8-bit characters. The code is used both to correct errors and to identify when the decoder has failed to produce a correct codeword. When this code is used on a memoryless binary symmetric channel, the probability of codeword error is 10(exp-5) when the channel bit error probability is 0.5%, and the probability of undetected decoder error is upper bounded by 2.8 (10-6) for all channel bit error probabilities. Synchronization acquisition, employing a 255-bit reference sequence, is far more tolerant to bit errors than the waveform itself. The probability of false synchronization in a random noise environment is less than 10(exp-6) when the correlator threshold is set at 90. With this threshold the probability of missed synchronization is less than 10(exp-6) for a 20% channel bit error probability. Synchronization performance is acceptable for truncated received sequences up to truncation levels of 50%.