# Gr-ieee802-11

**URL:** <https://www.ruby-forum.com/t/gr-ieee802-11/232152>\
**Category:** GNU Radio\
**Created:** [September 21, 2014, 9:27am UTC](https://www.ruby-forum.com/t/gr-ieee802-11/232152 "2014-09-21T09:27:19Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [September 21, 2014, 9:27am UTC](https://www.ruby-forum.com/t/gr-ieee802-11/232152/1 "2014-09-21T09:27:19Z")

</div>

Hi all,

I would like to overcome a limitation of gr-ieee802-11, which is due to  
the fact it must copy a fixed amount of samples in the ofdm\_sync\_short  
block; the consequence of this is that is non possible to capture all of  
the wifi frame on the air; if you copy 40 sym and there was a frame  
start after 35 sym you lose it. At the moment I have failed to overcome  
this limitation, so I’m asking if someone can point me in the right  
direction.

I’m experimenting with this great work, in the area of 802.11a rtx using  
my B200 at 20Msps and my home 802.11a modem. For experimenting purpose,  
I have implemented 2 blocks, one for frequency offset estimation and  
correction, and one for equalization based on pilot carriers. I have  
also modified ofdm\_sync\_long to add LT frequency correction. My work is  
based on paper “Frequency Offset Estimation and correction in the  
802.11a WLAN (2004)”, wich you can find on the web. I can see a lot of  
traffic at 6Mbit bpsk, but not all of the frames, and frequency offset  
correction can reach 200khz of cfo with correct decoding.

thanks in advance

Stefano