[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Discuss-gnuradio] BER in bert- example
From: |
Daniel Bartel |
Subject: |
Re: [Discuss-gnuradio] BER in bert- example |
Date: |
Wed, 27 Apr 2011 08:49:54 +0200 |
>>> But from my tests I see that
>>> 1 bit error in -> 7 bit errors out
>>> 2 consecutive bit errors in -> 2 errors in the output
>>> 3 consecutive bit errors in -> 7 errors in the output
>>> 4 consecutive bit errors in -> 4 errors in the output
>>> ...
>>> And so forth up to 7 (Length of the lfsr)
>>>
>>> The reason I ask is that if I want to change the scrambler and/or the
>>> modulation, I assume that this "magic number" will change as well.
>>
>> 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 descrambler
If I'm wrong, don't hesitate to correct me. Thanks.
Daniel
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- Re: [Discuss-gnuradio] BER in bert- example,
Daniel Bartel <=