Sense data backfill and WiFi SNR


I have complained for a long time that my data doesn’t backfill when Sense comes back online (even if it was not connected to Sense’s servers for just 30 minutes).

The first thing I did was to ensure that my Sense stayed on my WiFi network during these periods. For this, I setup a cron job that ARPinged the Sense unit once every minute, and logged the data. I could not use ping because the Sense unit does not respond to icmp-echo-request packets. Nonetheless, ARPing indicated no apparent connectivity issues at my end.

The next thing I did was to log the SNR for Sense by recording the general background dBm and the RSSI for the Sense unit over 24 hours. This script ran every 5 minutes. The average background was -87 dBm, and the average RSSI at the Sense unit was -68 dBm. So the average SNR is 19 dB, which I thought wasn’t bad.

But, a very helpful fellow-Sense user, Dave Sherrington (@dave_n_s), suggested I look into a poor WiFi signal as a possible issue. So, I did that last night. The closest AP to the Sense unit, which is in my garage, is several walls away. I wasn’t inclined to add an AP to the garage until I had some indication signal strength was an issue, so I replaced the antenna on the Sense with a 9 dBi directional antenna, and aimed it toward the AP that’s in my exercise/cat room. Over the last 20 hours, the SNR for Sense has ranged between 22-30, with an average of 24 dB.

While I was setting up the new antenna, Sense wasn’t transmitting data to the servers for about 35 minutes, which showed up as a gap in the data. But, I was pleasantly surprised that the data backfilled just fine - so the gap disappeared. I did a second test early this morning where I disconnected my cable modem for 30 minutes. That data backfilled also.

So @dave_n_s - thank you very much!!

And everyone else - measure the SNR for your Sense. 19-20 dB is sufficient for general internet browsing and pulling email, but clearly the volume of data sent by Sense needs a higher SNR - my experience indicates at least 23-24 dB. Also, while that difference seems small - it’s a log scale.

Sense Monitor Offline. Two flashing red lights

Thanks! Can you share a link to the model of antenna you used so we can easily make similar upgrades?

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I put another Ubiquiti UniFi AP AC Lite access point in our basement to help the Sense out. Thankfully it also makes my wife happy as Netflix now works more consistently while she’s on the cardio equipment down there. :slight_smile:

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