OFDM and SNR EST

GNU Radio
1

Dear all,

we are trying to use the block digital_mpsk_snr_est in an OFDM
flowgraph.
We think that the right place for the snr_est is after the
ofdm_frame_sink
however we have the following error:

itemsize mismatch: ofdm_frame_sink(27):0 using 1600,
mpsk_snr_est_cc(28):0
using 8

(consider that we have 200 occupied tones and hence 1600 is 200*8)

Do you have any idea?

Thank you
Vanessa

2

On Fri, Aug 3, 2012 at 10:36 AM, Vanessa Gardellin
[email protected] wrote:

Do you have any idea?

Thank you
Vanessa

Vanessa,

I don’t think that the mpsk_snr_est is really appropriate for OFDM.
It’d probably work if you applied it directly to one subcarrier, but
definitely not the entire symbol. It really is designed for MPSK
signals, after all.

There are other methods for measuring OFDM SNR that I’ve seen in
papers; of course, I can’t recall what they are off the top of my
head, but they definitely exist. So I’d spend my time looking at
algorithms that are specific to OFDM instead of trying to cram the
MPSK SNR ests into it.

Tom