Re: [Discuss-gnuradio] OFDM results.

[Bob McGwier]

In your sixteen QAM and other figures I see two effects.

Notice just the slightest hint that arcs through the top four 
constellation points in the 16 QAM is not straight.  This curvature is 
caused by nonlinearity.

Your result almost surely can NOT be clock jitter.  If you had a lot of 
clock jitter,  the pictures would look much worse.  Notice the 
dispersion gets larger as your proceed away from the origin.  This is 
almost surely phase noise in some oscillator.

Bob


Per Zetterberg wrote:
> Dear all,
>
> I am experimenting with OFDM between two USRPs. Unfortunately, I am not yet
> able to master the gnuradio framework so I have made my own implementation.
> The results are given in the link below.
>
> http://www.s3.kth.se/~perz/usrp/OFDM_results.pdf
>
>
> How does this compare with the gnuradio OFDM implementation ?
>
> What is the cause of the problems. Clock jitter ?, non-linearities ?
>
>
> BR/
> Per Zetterberg
>
>
>
>
>
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