Re: Missings packets on OFDM system simulation

[Johannes Demel]

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>>) 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?

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