1- So, you have an SNR of best-case 16 dB; that's not high for an OFDM
system.
2- No, there's no power normalization. Hint: you can look all this up
by actually looking inside these blocks! This would make a lot of
sense, since it sounds you don't actually want to use tzhe OFDM blocks
at all. The whole advantage of the OFDM blocks compared to just doing
an IFFT of your transmit vector is that you get a header and modulation
scheme.
3- Not quite sure what "information is linearly related to complex
symbols" means? Can you elaborate?
3b- A case where you *don't* do FEC is either a non-communications
system (i.e. you don't actually want to do OFDM for the reason of
transmitting information) or the extremely-bad-SNR case (where FEC
makes your BER better). For both cases, the existing OFDM blocks are
more of an obstacle than a solution.
What are you building? What is your overall application. Please paint
the bigger picture – it's a bit frustrating to try to help you, but
then only get told that "this is not how I want to do it".
Best regards,
Marcus
On Sat, 2019-05-25 at 18:39 +0200, Marcus Müller wrote:
Dear Farid,
please always respond on the mailing list.
Thank you,
Marcus Müller
On Sat, 2019-05-25 at 17:36 +0100, farid mihoub wrote:
> 1- For the noise : in the TX side the output is in the order of 2A,
> the noise 0.05A.
> 2-Second even without noise, the const does not affect the
> transmission, is there any sort of power normalization?
> 3-For the FEC and the modulation I want to try my custom mapping
> where information is linearly related to complex symbols, and my
> application doesn't require error correction.
>
> Thank you.
>
>
> 25.05.2019, 17:06, "Marcus Müller" <address@hidden>:
> > Hello Farid,
> > On Sat, 2019-05-25 at 15:59 +0100, farid mihoub wrote:
> > > Hello,
> > >
> > > In the OFDM_tx, rx examples in gr-digital :
> > > 1- Why just a low level of noise affect the transmission and
> > > cause it
> > > to stop.
> >
> > "low" is relative. It seems it's high enough to cause packet
> > losses,
> > iff it's actually the noise.
> >
> > > 2- in the the Tx output and the Rx input no matter the value
> > > of
> > > the
> > > multiply constant we apply
> > > that would not affect our transmission.
> >
> > Then it's probably not only the noise!
> >
> > > 3- Is there any way to separate channel estimation and
> > > tracking
> > > from
> > > data transmission, sometime I get the error "invalid packet
> > > detected!" form the packet parser, also I need my data to
> > > bypass
> > > FEC
> > > and QAM.
> >
> > Um, prior to QAM demodulation there is no data, and prior to FEC
> > decoding there is no information bits, so I'm not sure what you
> > want?
> >
> > > My purpose is to stream raw complex data to the I/Q
> > > components
> > > directly.
> >
> > Then it seems you don't want an OFDM transceiver but maybe just
> > simply
> > a single IFFT? Not quite sure what you have in mind.
> >
> > Best regards,
> > Marcus
> >
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