On Aug 16, 12:15�pm, "magouliana" <h...@in.gr> wrote:

> >On Aug 16, 9:34=A0am, "magouliana" <h...@in.gr> wrote:
> >> Hi,
> >> I am trying to simulate a Reed-Solomon simulation over AWGN channel.
> >> When I plot the BER vs SNR the line stops every time in SNR 7db with
> BER
> >> almost 5*10^-5. I want the BER to be smaller than 10^-6.
> >> I tried to run for more codewords (e.x 10000) but the line stopped
> again
> >> at 5*10^-5.
> >> Any suggestions?
> >> Thanks.
>
> >Without any information on how you are doing your simulation,
> >it's hard to suggest anything.
>
> >What do you mean by "the line stops". �Are you saying that your
> >simulation stops at SNR =3D 7 dB, or what you are not able to estimate
> >results showing BER below 5e-5?
>
> Thanks for the reply,
> Here is the output of the simulation,
>
> �>> 1 � � : SNR = 0.0dB, �BER = 1.44e-001
> �>> 2 � � : SNR = 1.0dB, �BER = 1.12e-001
> �>> 3 � � : SNR = 2.0dB, �BER = 7.60e-002
> �>> 4 � � : SNR = 3.0dB, �BER = 4.57e-002
> �>> 5 � � : SNR = 4.0dB, �BER = 1.63e-002
> �>> 6 � � : SNR = 5.0dB, �BER = 4.25e-003
> �>> 7 � � : SNR = 6.0dB, �BER = 6.02e-004
> �>> 8 � � : SNR = 7.0dB, �BER = 0.00e+000
> �>> 9 � � : SNR = 8.0dB, �BER = 0.00e+000
> ..
> As you can see the BER becomes zero at SNR=7dB as a result the draw line
> stops at SNR=6dB, I have to represent a figure that BER will be smaller
> than 10^-6. I �tried to run it for more codewords 10000 for exapmle (this
> example is with 1000) to produce more errors �but the result is still the
> same.

Um. If you are trying to reliably characterize an event that happens
once every 10^5 times, you'll need to test in the order of several
orders
of magnitude higher than 10^5, right?
Are you re-setting the random number generator's seed every once in
a while?
Sounds to me that you just have to be more patient and run more
simulations.

Reply by Eric Jacobsen●August 16, 20082008-08-16

On Sat, 16 Aug 2008 12:15:19 -0500, "magouliana" <helo@in.gr> wrote:

>>On Aug 16, 9:34=A0am, "magouliana" <h...@in.gr> wrote:
>>> Hi,
>>> I am trying to simulate a Reed-Solomon simulation over AWGN channel.
>>> When I plot the BER vs SNR the line stops every time in SNR 7db with
>BER
>>> almost 5*10^-5. I want the BER to be smaller than 10^-6.
>>> I tried to run for more codewords (e.x 10000) but the line stopped
>again
>>> at 5*10^-5.
>>> Any suggestions?
>>> Thanks.
>>
>>Without any information on how you are doing your simulation,
>>it's hard to suggest anything.
>>
>>What do you mean by "the line stops". Are you saying that your
>>simulation stops at SNR =3D 7 dB, or what you are not able to estimate
>>results showing BER below 5e-5?
>>
>
>Thanks for the reply,
>Here is the output of the simulation,
>
> >> 1 : SNR = 0.0dB, BER = 1.44e-001
> >> 2 : SNR = 1.0dB, BER = 1.12e-001
> >> 3 : SNR = 2.0dB, BER = 7.60e-002
> >> 4 : SNR = 3.0dB, BER = 4.57e-002
> >> 5 : SNR = 4.0dB, BER = 1.63e-002
> >> 6 : SNR = 5.0dB, BER = 4.25e-003
> >> 7 : SNR = 6.0dB, BER = 6.02e-004
> >> 8 : SNR = 7.0dB, BER = 0.00e+000
> >> 9 : SNR = 8.0dB, BER = 0.00e+000
>..
>As you can see the BER becomes zero at SNR=7dB as a result the draw line
>stops at SNR=6dB, I have to represent a figure that BER will be smaller
>than 10^-6. I tried to run it for more codewords 10000 for exapmle (this
>example is with 1000) to produce more errors but the result is still the
>same.

The BER curves for Reed-Solomon codes or concatenated code with outer
Reed-Solomon codes get quite steep in their operating range. In
other words, at some point increasing the SNR a little bit improves
the BER a lot. When you're on that part of the curve and the error
rate starts dropping to the 10e-6 to 10e-9 region, it takes a long
time to accumulate enough errors in simulation to verify performance.
I've not plotted the points you listed, but doing so on a log scale
should allow you to graphically extrapolate a reasonable expected
error rate for SNRs of 7dB an better. You may need to run a
simulation a long time to get that error rate, and at some point
everyone gives up and just plots enough points to show the expected
trend.
People who claim to have simulated, or even measured, error rates in
the 10e-9 or better region are often met with justifiable suspiscion
since the tests are often just not practical. I know of one case
where a technology company claimed to have tested operating equipment
in the lab to 10e-10 (or something like that, I don't remember the
exact figure). I pointed out to some potential investors that at the
claimed data rates and error metric those tests would have taken much
longer than the the company had been in existence.
At some point it just doesn't matter, so testing and simulation really
only needs to be done to the point where there's confidence that
things are as they should be.
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.ericjacobsen.org
Blog: http://www.dsprelated.com/blogs-1/hf/Eric_Jacobsen.php

Reply by Moti Litochevski●August 16, 20082008-08-16

On Aug 16, 7:15�pm, "magouliana" <h...@in.gr> wrote:

> >On Aug 16, 9:34=A0am, "magouliana" <h...@in.gr> wrote:
> >> Hi,
> >> I am trying to simulate a Reed-Solomon simulation over AWGN channel.
> >> When I plot the BER vs SNR the line stops every time in SNR 7db with
> BER
> >> almost 5*10^-5. I want the BER to be smaller than 10^-6.
> >> I tried to run for more codewords (e.x 10000) but the line stopped
> again
> >> at 5*10^-5.
> >> Any suggestions?
> >> Thanks.
>
> >Without any information on how you are doing your simulation,
> >it's hard to suggest anything.
>
> >What do you mean by "the line stops". �Are you saying that your
> >simulation stops at SNR =3D 7 dB, or what you are not able to estimate
> >results showing BER below 5e-5?
>
> Thanks for the reply,
> Here is the output of the simulation,
>
> �>> 1 � � : SNR = 0.0dB, �BER = 1.44e-001
> �>> 2 � � : SNR = 1.0dB, �BER = 1.12e-001
> �>> 3 � � : SNR = 2.0dB, �BER = 7.60e-002
> �>> 4 � � : SNR = 3.0dB, �BER = 4.57e-002
> �>> 5 � � : SNR = 4.0dB, �BER = 1.63e-002
> �>> 6 � � : SNR = 5.0dB, �BER = 4.25e-003
> �>> 7 � � : SNR = 6.0dB, �BER = 6.02e-004
> �>> 8 � � : SNR = 7.0dB, �BER = 0.00e+000
> �>> 9 � � : SNR = 8.0dB, �BER = 0.00e+000
> ..
> As you can see the BER becomes zero at SNR=7dB as a result the draw line
> stops at SNR=6dB, I have to represent a figure that BER will be smaller
> than 10^-6. I �tried to run it for more codewords 10000 for exapmle (this
> example is with 1000) to produce more errors �but the result is still the
> same.

It looks like your results are just fine.
You can take a look at the application note by AHA regarding Reed-
Solomon codes to evaluate the expected results (link:
http://www.aha.com/show_pub.php?id=39).
The BER at the output of the RS decoder is very low (depending on the
exact code you are using) as the input BER gets better.
For this code it is relatively easy to evaluate the code performance
analytically instead of obtaining it using simulation. I do not think
it is worth while running very long simulations to evaluate the code
performance.
Moti

Reply by magouliana●August 16, 20082008-08-16

>On Aug 16, 9:34=A0am, "magouliana" <h...@in.gr> wrote:
>> Hi,
>> I am trying to simulate a Reed-Solomon simulation over AWGN channel.
>> When I plot the BER vs SNR the line stops every time in SNR 7db with

BER

>> almost 5*10^-5. I want the BER to be smaller than 10^-6.
>> I tried to run for more codewords (e.x 10000) but the line stopped

again

>> at 5*10^-5.
>> Any suggestions?
>> Thanks.
>
>Without any information on how you are doing your simulation,
>it's hard to suggest anything.
>
>What do you mean by "the line stops". Are you saying that your
>simulation stops at SNR =3D 7 dB, or what you are not able to estimate
>results showing BER below 5e-5?
>

Thanks for the reply,
Here is the output of the simulation,
>> 1 : SNR = 0.0dB, BER = 1.44e-001
>> 2 : SNR = 1.0dB, BER = 1.12e-001
>> 3 : SNR = 2.0dB, BER = 7.60e-002
>> 4 : SNR = 3.0dB, BER = 4.57e-002
>> 5 : SNR = 4.0dB, BER = 1.63e-002
>> 6 : SNR = 5.0dB, BER = 4.25e-003
>> 7 : SNR = 6.0dB, BER = 6.02e-004
>> 8 : SNR = 7.0dB, BER = 0.00e+000
>> 9 : SNR = 8.0dB, BER = 0.00e+000
..
As you can see the BER becomes zero at SNR=7dB as a result the draw line
stops at SNR=6dB, I have to represent a figure that BER will be smaller
than 10^-6. I tried to run it for more codewords 10000 for exapmle (this
example is with 1000) to produce more errors but the result is still the
same.

Reply by John●August 16, 20082008-08-16

On Aug 16, 12:27 pm, Allan Herriman <allanherri...@hotmail.com> wrote:

> julius <juli...@gmail.com> wrote in news:b87e92d9-710d-48ba-90ce-
> 9a0f33f25...@w24g2000prd.googlegroups.com:
>
>
>
> > On Aug 16, 9:34 am, "magouliana" <h...@in.gr> wrote:
> >> Hi,
> >> I am trying to simulate a Reed-Solomon simulation over AWGN channel.
> >> When I plot the BER vs SNR the line stops every time in SNR 7db with BER
> >> almost 5*10^-5. I want the BER to be smaller than 10^-6.
> >> I tried to run for more codewords (e.x 10000) but the line stopped again
> >> at 5*10^-5.
> >> Any suggestions?
> >> Thanks.
>
> > Without any information on how you are doing your simulation,
> > it's hard to suggest anything.
>
> > What do you mean by "the line stops". Are you saying that your
> > simulation stops at SNR = 7 dB, or what you are not able to estimate
> > results showing BER below 5e-5?
>
> It's possible the OP is running into problems with the accuracy of the
> AWGN. Most generators don't have very good tails, falling to zero at only
> a few sigma away from the mean.
>
> Regards,
> Allan

Does that create an error floor?
John

Reply by Allan Herriman●August 16, 20082008-08-16

julius <juliusk@gmail.com> wrote in news:b87e92d9-710d-48ba-90ce-
9a0f33f25e50@w24g2000prd.googlegroups.com:

> On Aug 16, 9:34�am, "magouliana" <h...@in.gr> wrote:
>> Hi,
>> I am trying to simulate a Reed-Solomon simulation over AWGN channel.
>> When I plot the BER vs SNR the line stops every time in SNR 7db with BER
>> almost 5*10^-5. I want the BER to be smaller than 10^-6.
>> I tried to run for more codewords (e.x 10000) but the line stopped again
>> at 5*10^-5.
>> Any suggestions?
>> Thanks.
>
> Without any information on how you are doing your simulation,
> it's hard to suggest anything.
>
> What do you mean by "the line stops". Are you saying that your
> simulation stops at SNR = 7 dB, or what you are not able to estimate
> results showing BER below 5e-5?

It's possible the OP is running into problems with the accuracy of the
AWGN. Most generators don't have very good tails, falling to zero at only
a few sigma away from the mean.
Regards,
Allan

Reply by julius●August 16, 20082008-08-16

On Aug 16, 9:34�am, "magouliana" <h...@in.gr> wrote:

> Hi,
> I am trying to simulate a Reed-Solomon simulation over AWGN channel.
> When I plot the BER vs SNR the line stops every time in SNR 7db with BER
> almost 5*10^-5. I want the BER to be smaller than 10^-6.
> I tried to run for more codewords (e.x 10000) but the line stopped again
> at 5*10^-5.
> Any suggestions?
> Thanks.

Without any information on how you are doing your simulation,
it's hard to suggest anything.
What do you mean by "the line stops". Are you saying that your
simulation stops at SNR = 7 dB, or what you are not able to estimate
results showing BER below 5e-5?

Reply by magouliana●August 16, 20082008-08-16

Hi,
I am trying to simulate a Reed-Solomon simulation over AWGN channel.
When I plot the BER vs SNR the line stops every time in SNR 7db with BER
almost 5*10^-5. I want the BER to be smaller than 10^-6.
I tried to run for more codewords (e.x 10000) but the line stopped again
at 5*10^-5.
Any suggestions?
Thanks.