FPGA Central

Hi everybody,

I have a doubt that can be very obvious for you but it has driven m
crazy. I want to know the performance of my demodulator by calculating th
BER curve respect to the EbN0. For that, I input some signals at differen
EbN0 but how should I calculate the EbN0? My method for a complex signal
as I read several times, is:

Eb = S/R; where S is the signal power and R is the data rate
N0 = N/Fs where N is the variance^2 and Fs is the sampling frequency.

However, I've also seen that N0 = N/B where B is the bandwidth of th
channel. Comparing my BER curve with the theoretical one, it is quite fa
and I would like to be sure that my EbN0 calculation is 100% right and the
check the demodulator.

Could somebody please clear this point?
Thank you very much

Regards
mary

On Mar 25, 6:06*am, "m" <stuttbr...@hotmail.com> wrote:
> Hi everybody,
>
> I have a doubt that can be very obvious for you but it has driven me
> crazy. I want to know the performance of my demodulator by calculating the
> BER curve respect to the EbN0. For that, I input some signals at different
> EbN0 but how should I calculate the EbN0? My method for a complex signal,
> as I read several times, is:
>
> Eb = S/R; where S is the signal power and R is the data rate
> N0 = N/Fs where N is the variance^2 and Fs is the sampling frequency.
>
> However, I've also seen that N0 = N/B where B is the bandwidth of the
> channel. Comparing my BER curve with the theoretical one, it is quite far
> and I would like to be sure that my EbN0 calculation is 100% right and then
> check the demodulator.
>
> Could somebody please clear this point?
> Thank you very much
>
> Regards
> mary

Surprisingly, the explanation on the MathWorks' website is quite
good, and useful if you are simulating an AWGN channel in
discrete-time.

http://www.mathworks.com/support/sol...lution=1-19I4S

Hope this helps,
Julius

>On Mar 25, 6:06=A0am, "m" <stuttbr...@hotmail.com> wrote:
>> Hi everybody,
>>
>> I have a doubt that can be very obvious for you but it has driven me
>> crazy. I want to know the performance of my demodulator by calculatin
th=
>e
>> BER curve respect to the EbN0. For that, I input some signals a
differen=
>t
>> EbN0 but how should I calculate the EbN0? My method for a comple
signal,
>> as I read several times, is:
>>
>> Eb =3D S/R; where S is the signal power and R is the data rate
>> N0 =3D N/Fs where N is the variance^2 and Fs is the samplin
frequency.
>>
>> However, I've also seen that N0 =3D N/B where B is the bandwidth o
the
>> channel. Comparing my BER curve with the theoretical one, it is quit
far
>> and I would like to be sure that my EbN0 calculation is 100% right an
th=
>en
>> check the demodulator.
>>
>> Could somebody please clear this point?
>> Thank you very much
>>
>> Regards
>> mary
>
>Surprisingly, the explanation on the MathWorks' website is quite
>good, and useful if you are simulating an AWGN channel in
>discrete-time.
>
>http://www.mathworks.com/support/sol...olution=3D1-1=
>9I4S
>
>Hope this helps,
>Julius
>

Thank you for your answer. Then it is using the sampling frequency.
Regards

Maria

On Mar 25, 9:35*am, "m" <stuttbr...@hotmail.com> wrote:
> >On Mar 25, 6:06=A0am, "m" <stuttbr...@hotmail.com> wrote:
> >> Hi everybody,
>
> >> I have a doubt that can be very obvious for you but it has driven me
> >> crazy. I want to know the performance of my demodulator by calculating
> th=
> >e
> >> BER curve respect to the EbN0. For that, I input some signals at
> differen=
> >t
> >> EbN0 but how should I calculate the EbN0? My method for a complex
> signal,
> >> as I read several times, is:
>
> >> Eb =3D S/R; where S is the signal power and R is the data rate
> >> N0 =3D N/Fs where N is the variance^2 and Fs is the sampling
> frequency.
>
> >> However, I've also seen that N0 =3D N/B where B is the bandwidth of
> the
> >> channel. Comparing my BER curve with the theoretical one, it is quite
> far
> >> and I would like to be sure that my EbN0 calculation is 100% right and
> th=
> >en
> >> check the demodulator.
>
> >> Could somebody please clear this point?
> >> Thank you very much
>
> >> Regards
> >> mary
>
> >Surprisingly, the explanation on the MathWorks' website is quite
> >good, and useful if you are simulating an AWGN channel in
> >discrete-time.
>
> >http://www.mathworks.com/support/sol....html?solution...
> >9I4S
>
> >Hope this helps,
> >Julius
>
> Thank you for your answer. Then it is using the sampling frequency.
> Regards
>
> Maria

The confusion comes in simulating a sampled representation with
oversampling. N0 should be the *density* of the AWGN. Hence
there is scaling depending on the sampling rate.

After matched filtering, they should all come out to be the same
as the "width" of the matched filter in Hz is set according to the
symbol rate, not the sampling rate.

Julius

>On Mar 25, 9:35=A0am, "m" <stuttbr...@hotmail.com> wrote:
>> >On Mar 25, 6:06=3DA0am, "m" <stuttbr...@hotmail.com> wrote:
>> >> Hi everybody,
>>
>> >> I have a doubt that can be very obvious for you but it has drive
me
>> >> crazy. I want to know the performance of my demodulator b
calculating
>> th=3D
>> >e
>> >> BER curve respect to the EbN0. For that, I input some signals at
>> differen=3D
>> >t
>> >> EbN0 but how should I calculate the EbN0? My method for a complex
>> signal,
>> >> as I read several times, is:
>>
>> >> Eb =3D3D S/R; where S is the signal power and R is the data rate
>> >> N0 =3D3D N/Fs where N is the variance^2 and Fs is the sampling
>> frequency.
>>
>> >> However, I've also seen that N0 =3D3D N/B where B is the bandwidt
of
>> the
>> >> channel. Comparing my BER curve with the theoretical one, it i
quite
>> far
>> >> and I would like to be sure that my EbN0 calculation is 100% righ
and
>> th=3D
>> >en
>> >> check the demodulator.
>>
>> >> Could somebody please clear this point?
>> >> Thank you very much
>>
>> >> Regards
>> >> mary
>>
>> >Surprisingly, the explanation on the MathWorks' website is quite
>> >good, and useful if you are simulating an AWGN channel in
>> >discrete-time.
>>
>
>http://www.mathworks.com/support/sol....html?solution...
>> >9I4S
>>
>> >Hope this helps,
>> >Julius
>>
>> Thank you for your answer. Then it is using the sampling frequency.
>> Regards
>>
>> Maria
>
>The confusion comes in simulating a sampled representation with
>oversampling. N0 should be the *density* of the AWGN. Hence
>there is scaling depending on the sampling rate.
>
>After matched filtering, they should all come out to be the same
>as the "width" of the matched filter in Hz is set according to the
>symbol rate, not the sampling rate.
>
>Julius
>

Just to be sure. The signal that I want to measure the Eb/N0 i
oversampled, I have 10 samples per bit, so:
Eb/N0 = (S/R)/(N/Fs) = (S/N)*(Fs/R) = (S/N)*10;

is that right? My demodulator is for GMSK and I'm not using a matche
filter. Is that a problem?

Thank you very much for your answer Julius
Regards

Mary