Re: [Discuss-gnuradio] gr-ieee802-11 wifi signal bitrate

[Bastian Bloessl]

Hi,


> On 8. May 2017, at 09:00, Thom L <address@hidden> wrote:
> 
> IIRC, it shows the autocorrelation of the signal. If you add a trigger to the 
> default plot (level ~0.56) you should see the characteristic plateau of the 
> short training sequence at the beginning of frames (this is used for frame 
> detection).
> 
> Ok that's right? But I don't understand very well the signification of the 
> “plateau”

The  characteristic plateau of the autocorrelation is used for frame detection 
by the Sync Short block. The plot can sometimes help to debug issues with it. 
For example, it can be used to
- roughly adjust the gain even if synchronization / decoding does not work 
(i.e. if there are no subcarrier constellations)
- often people experience a DC offset or LO leakage. In that case the 
autocorrelation is always high, which is directly visible in the plot.
- determine a threshold for frame detection
Also, I hoped, it might be helpful to better understand what the Sync Short 
block is locking for.

Best,
Bastian