Re: [Discuss-gnuradio] references using in ofdm_equalizer_simpledfe

[Aditya Dhananjay]

On Thu, Sep 4, 2014 at 9:04 AM, Tiankun Hu <address@hidden> wrote:

Hi Martin,
Could you tell me the reference paper that you used in ofdm_equalizer_simpledfe?

​Hello Tiankun,

A decision feedback equalizer (DFE) works like this:

The equalizer keeps track of the channel estimate on every subcarrier​ i. Call this estimate H_i. The initial values of H_i are provided by the Schmidl-Cox block, and these values are calculated from the SYNC symbols present in every packet.

Now, when a symbol r_i is received on subcarrier i, it is equalized using the estimate H_i. The equalized symbol is matched to the nearest constellation point. Let this symbol be R_i. Now, the new estimate of H_i is calculated from r_i and R_i. This new value of H_i is then used for the next symbol on subcarrier i.

DFE works well when the channel changes slowly across time. However, if there is substantial residual CFO (carrier frequency offset) or Doppler, then errors are possible. Substantial channel variations across subcarrier indices is irrelevant, because DFE maintains an independent channel estimate H_i for each subcarrier i.

Good luck with GNU Radio. :)

Best,

Aditya