Re: BER in bert- example

If you want a good BER measurement, I wouldn’t use the method that you
describe here.

You are correct. The scrambler introduces three output errors per
input error for single channel errors that are farther apart than the
length of the shift register. This is the case once the shift
register has already achieved self-synchronization and at low channel
error rates. For the purposes of the simple BERT example, this was
sufficient. (The number 3 comes from the number of taps in the
scrambler polynomial.)

I know this thread is a bit old, but is it possible that there is an
mistake in the text?

I think it should be written, that 1 bit error in the scramber input
introduces 4 errors in the output, because 1 error is passed directly
through and 3 feedback errors are introduced by the taps in the
scrambler polynomial of:

self._descrambler = gr.descrambler_bb(0x8A, 0x7F, 7) # CCSDS 7-bit

If I’m wrong, don’t hesitate to correct me. Thanks.


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