Hi Johannes,
I'm not sure what you mean with "Did you check the actual sample level on the "OFDM
Transmitter" output port?" but in the output of the OFDM transmitter block I got about 15
[dBW], this measurement was done like this: OFDM Transmitter -> complex to mag^2 -> moving
average -> 10log(input) -> file sink
For the SNR, I calculate it with the attach flowgraph and test different levels of ''Noise
Voltage", I can share the values if need it.
i understand that adding noise it results in losing packets, but I don't think it should
be that aggressive, i really think there is something that I'm doing wrong or not seeing
thanks for your time and comments
kindly
Jorge
El vie, 14 jul 2023 a las 4:12, Johannes Demel (<demel@ant.uni-bremen.de
<mailto:demel@ant.uni-bremen.de>>) escribió:
Hi Jorge,
a couple of observations first:
- the "throttle" block needs to be part of the actual flowgraph to have
any effect. You might want to remove your null source -> throttle ->
null sink chain.
- for the sake of a Minimum Working Example (MWE) I suggest to remove
the file sink and virtual sinks as well.
- Did you check the actual sample level on the "OFDM Transmitter" output
port? I suspect these values do not have a mean energy of 1 but way
less. In your case probably 1/sqrt(64). You'd need to adopt the "Noise
Voltage" parameter in your "Channel Model" block accordingly.
- How did you compute your SNR value?
- As long as there's noise, you'd eventually lose packets.
Cheers
Johannes
On 13.07.23 20:08, JORGE GONZALEZ ORELLANA via GNU Radio, the Free &
Open-Source Toolkit for Software Radio wrote:
> As you can see, it's the basic implementation of OFDM.
> My goal it's to measure the BER, but as I mentioned earlier, below
> certain level or SNR (20dB)
>
> El jue, 13 jul 2023 a las 8:05, Marcus Müller (<mmueller@gnuradio.org
<mailto:mmueller@gnuradio.org>
> <mailto:mmueller@gnuradio.org <mailto:mmueller@gnuradio.org>>>) escribió:
>
> Hi Jorge,
>
> yes, please share your flowgraph. It's moot even beginning talking
> about it without
> knowing it.
>
> Best regards,
> Marcus
>
> On 12.07.23 20:53, JORGE GONZALEZ ORELLANA via GNU Radio, the Free &
> Open-Source Toolkit
> for Software Radio wrote:
> > Hello everyone, I have some question related with a OFDM
> transmission simulation, in
> > particular, about losing packets.
> >
> > I am using the OFDM Transmitter and Receiver blocks to do the
> transmission (if you need
> > more details, I can upload an image of the flowgraph).
> >
> > The problem that I get is when put some noise (to get some level
> of SNR), when I have
> > about 20dB (or more) of SNR I don't lose any packet, but if I put
> less than 20dB of SNR,
> > almost all packets gets lost, (just 1 or 2 packets are received),
> all of this happen over
> > simulation.
> >
> > Any suggestions on why this might happen?
>