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#1 2019-Feb-19 10:05:48

Yan Wang
Member
Registered: 2018-Oct-25
Posts: 21

802.11 Reference Design: log capture and channel estimate viewer

Hello,

After I configured the two WARP boards using "Mango_802.11_RefDes_v1.7.8.zip". I tried to compute the "log_capture_two_node_two_flow.py" without any change to generate two log files. The two nodes keep static.  Then I use the "chan_est_to_HDF5.py" to convert the raw log file to MATLAB compatible file and use the MATLAB script "ofdm_chan_est_viewer.m" to observe the result. The following figure is the configuration of equipment.
https://upload.cc/i1/2019/02/19/3wA0TV.jpeg

However, when I look at the results in MATLAB, I found that the received power is almost smaller than the achieved sensitivity as can be seen in the figure.

https://upload.cc/i1/2019/02/19/5FHZsG.png
Thus, why does this happen?

Best regards,
Yan

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#2 2019-Feb-19 13:50:09

murphpo
Administrator
From: Mango Communications
Registered: 2006-Jul-03
Posts: 5159

Re: 802.11 Reference Design: log capture and channel estimate viewer

The Rx Power is estimated from the RSSI and radio Rx gains. The gains in your screenshot are high (max RF gain = 30, max BB gain = 63), indicating the AGC observed a lower power signal during the packet preamble. There are many possibilities. For example, is the Tx power set low? Do the antennas support your current center frequency? Are the antennas connected properly (i.e. antennas have SMA plugs, not RP-SMA plus)? A good debugging experiment would be to replace the antennas with a cable + attenuator (*always* have >30dB attenuation between Tx/Rx when using a cable). You could also directly test the Tx power using a spectrum analyzer.

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