Re: [Discuss-gnuradio] BER in bert- example

[Johnathan Corgan]

On Sun, Jan 31, 2010 at 06:52, Brian Padalino <address@hidden> wrote:

>> 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.)

Johnathan