Abstract:The characteristic of residuary bit errors in satellite baseband channel affects the performance of communication protocol in upper layers significantly. By system simulation and analyzing the bit error patterns, the probability distribution function (PDF) of bit errors occurrence and PDF of bit errors length are obtained. In typical satellite communication systems against the Rician fading channel, the PDF of bit errors occurrence approximates generalized extreme value distribution. But in Gaussian noise channel, the PDFs of bit errors occurrence and bit errors length approximate negative binomial distributions. Base on these fitting distributions, the baseband channel emulator provides a convenient method for system testing, which imposes residuary bit errors pattern on data stream reasonably.