forward error correction capabilities?

Started by owpex December 21, 2009
Hello

I wanted to know the difference that can exist between(among) a flow of
bits that goes out of a decodificador viterbi + Reed solomon and the flow
of bits originally in a transmission of tdt cofdm 

That is to say: do I obtain the same result to the exit of the corrector
Reed Solomon with a BER before Viterbi of 9-6 that with a BER before
Viterbi of 2-2?

Said otherwise:

Do I obtain the same result to the exit of the corrector Reed Solomon with
a BER after Viterbi of 9-6 that with a BER after Viterbi of 2-2?

Muchisimas thank you 


On 12/21/2009 7:01 AM, owpex wrote:
> Hello > > I wanted to know the difference that can exist between(among) a flow of > bits that goes out of a decodificador viterbi + Reed solomon and the flow > of bits originally in a transmission of tdt cofdm > > That is to say: do I obtain the same result to the exit of the corrector > Reed Solomon with a BER before Viterbi of 9-6 that with a BER before > Viterbi of 2-2? > > Said otherwise: > > Do I obtain the same result to the exit of the corrector Reed Solomon with > a BER after Viterbi of 9-6 that with a BER after Viterbi of 2-2? > > Muchisimas thank you > >
Short answer: no. You should be able to find via some google searches plots of BER vs Eb/No or BER vs SNR for a typical Viterbi decoder, typical Reed-Solomon (only) decoder, and typical concatenated CC-RS system with a Viterbi decoder and RS decoder. In all cases the curves have a slope, so there is a transfer function of input BER to output BER. For the Viterbi decoder by itself the slope is not as steep as it is with a system that uses an RS decoder, either by itself or concatenated with a Viterbi, but there is still a slope. The slope gets difficult to measure below error rates of 10e-9 or 10e-10 or so just because the tests take so long to run, and at some point in a practical system the limits of the dynamic range and noise floor will be reached. So there should always be a difference in output error rate if there is a difference in input error rate. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com

Eric Jacobsen wrote:


> The slope gets difficult to measure below error rates of 10e-9 or 10e-10 > or so just because the tests take so long to run, and at some point in a > practical system the limits of the dynamic range and noise floor will be > reached.
Brute force simulation isn't practical for low BERs, however it is simple enough to derive the estimates in that case. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
On 12/21/2009 10:17 AM, Vladimir Vassilevsky wrote:
> > > Eric Jacobsen wrote: > > >> The slope gets difficult to measure below error rates of 10e-9 or >> 10e-10 or so just because the tests take so long to run, and at some >> point in a practical system the limits of the dynamic range and noise >> floor will be reached. > > Brute force simulation isn't practical for low BERs, however it is > simple enough to derive the estimates in that case. > > Vladimir Vassilevsky > DSP and Mixed Signal Design Consultant > http://www.abvolt.com
Even with real equipment running real-time it's hard to measure 10e-9 or below with most system. -- Eric Jacobsen Minister of Algorithms Abineau Communications http://www.abineau.com

Eric Jacobsen wrote:
> On 12/21/2009 10:17 AM, Vladimir Vassilevsky wrote: >> Eric Jacobsen wrote: >> >>> The slope gets difficult to measure below error rates of 10e-9 or >>> 10e-10 or so just because the tests take so long to run, and at some >>> point in a practical system the limits of the dynamic range and noise >>> floor will be reached. >> >> >> Brute force simulation isn't practical for low BERs, however it is >> simple enough to derive the estimates in that case. >> > Even with real equipment running real-time it's hard to measure 10e-9 or > below with most system.
For real or simulated system, the case of marginally low BER is tractable. So the expected BER can be estimated from noise floor and code performance. There is no need to make long runs unless the goal is verification of the decoder operation. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
My interest takes root in knowing the qualit diferencia of image
between(among) a sign, for example, with BER before Viterbi of 1e-6 and
other one with BER of 1e-2 
From the point of view of the technician installer is interesting to be
able to offer to a client the major quality of possible image, but visually
it is very difficult to know the quality of a digital image 
If an image with BER before Viterbi of 1e-6 has almost the same quality
that one of BER before Viterbi of 1e-2 probably does not deserve to the
pena to invest(invert) in improving the quality of receipt looking for
better emplacements for to the antena since this work podrian it being done
by the correctors Viterbi and Reed Solomon 

Thank you  very much and sorry  for my translator-english
On Dec 26, 7:59&#2013266080;pm, "owpex" <chipko...@hotmail.com> wrote:
...
> > Thank you &#2013266080;very much and sorry &#2013266080;for my translator-english
i ain't never even heard of no "decodificador" beferr. i wonders what them things is. where can i pick me up one of them decodificadors? maybe at the same place where i get my Kalman filters, are they expensive? ;-) r b-j
On 27 Des, 03:23, robert bristow-johnson <r...@audioimagination.com>
wrote:
> On Dec 26, 7:59&#2013266080;pm, "owpex" <chipko...@hotmail.com> wrote: > ... > > > > > Thank you &#2013266080;very much and sorry &#2013266080;for my
translator-english
> > i ain't never even heard of no "decodificador" beferr. &#2013266080;
Give the guy a break. Given his two posts, it seems he is for real and actually have used some translator-bot to translate the message from whatever his native language is. I can hardly imagine the reverses situation where I were forced to formulate a question in, say, Japanese to get help. Rune

Rune Allnor wrote:

> On 27 Des, 03:23, robert bristow-johnson <r...@audioimagination.com> > wrote: >>On Dec 26, 7:59 pm, "owpex" <chipko...@hotmail.com> wrote: >> >>>Thank you very much and sorry for my translator-english >> >>i ain't never even heard of no "decodificador" beferr. > > > Give the guy a break. > > Given his two posts, it seems he is for real and actually > have used some translator-bot to translate the message from > whatever his native language is. I can hardly imagine the > reverses situation where I were forced to formulate a question > in, say, Japanese to get help.
Translate the question through Babelfish twice: in forward and in backward direction. Modify the original text until the output will be more or less sensible; hopefully it will be reasonable in Japanese as well. Perhaps, such procedure of optimization could be automated. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
Vladimir Vassilevsky  <nospam@nowhere.com> wrote:

>Translate the question through Babelfish twice: in forward and in >backward direction.
That's the BCJR algorithm isn't it? Steve