Inconsistent WiFi scanning and "Ghost" ESSID's

On a Jetson TX-1 we are seeing very inconsistent WiFi performance. To troubleshoot I ran this small script to repeatedly show signal strength for nearby AP’s:

while true; do sudo iwlist wlan0 scan | egrep 'Cell |Encryption|Quality|Last beacon|ESSID|Frequency' >> wifiscan; sleep 3; echo "-----" >> wifiscan; done

In the output below there are a few issues I am trying to understand:

  1. Several entries have ESSID:"". I don’t see these empty SSID’s with any of several WiFi analyzer tools running on co-located (same desk) Android, iOS and Linux machines.

  2. The empty ESSID’s sometimes share a MAC address, or are very close to other MAC addresses (for example lines 5/6, 50/51) below.

  3. The signal level is sometimes shown as 0dBm and Quality 70/70 (lines 10/11, 18, 50/51) for both valid and empty SSID’s. At other times a different (and likely more legitimate) signal level is shown.

This occurs on a stock TX-1 Devkit with the stock antennas and has been verified on two different TX-1’s, both with the -400 serial number suffix. Are these normal occurrences?

Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=58/70  Signal level=-52 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 100ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=25/70  Signal level=-85 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 100ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=65/70  Signal level=-45 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 100ms ago
Cell 04 - Address: B2:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 14380ms ago
Cell 05 - Address: 00:1D:D5:8B:AC:50 Frequency:2.412 GHz (Channel 1) Quality=21/70  Signal level=-89 dBm  Encryption key:on ESSID:"Stefano" Extra: Last beacon: 4840ms ago
Cell 06 - Address: 02:1D:D5:8B:AC:50 Frequency:2.412 GHz (Channel 1) Quality=18/70  Signal level=-92 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 14380ms ago
Cell 07 - Address: DC:EF:09:3C:ED:91 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"NETGEAR61_EXT" Extra: Last beacon: 100ms ago
-----
Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=58/70  Signal level=-52 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 90ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 90ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 90ms ago
Cell 04 - Address: 00:1D:D5:8B:AC:50 Frequency:2.412 GHz (Channel 1) Quality=21/70  Signal level=-89 dBm  Encryption key:on ESSID:"Stefano" Extra: Last beacon: 9580ms ago
Cell 05 - Address: DC:EF:09:3C:ED:91 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"NETGEAR61_EXT" Extra: Last beacon: 4840ms ago
Cell 06 - Address: BC:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"HOME-3A02" Extra: Last beacon: 90ms ago
-----
Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=58/70  Signal level=-52 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 90ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=26/70  Signal level=-84 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 90ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 90ms ago
Cell 04 - Address: 00:1D:D5:8B:AC:50 Frequency:2.412 GHz (Channel 1) Quality=21/70  Signal level=-89 dBm  Encryption key:on ESSID:"Stefano" Extra: Last beacon: 14300ms ago
Cell 05 - Address: DC:EF:09:3C:ED:91 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"NETGEAR61_EXT" Extra: Last beacon: 9560ms ago
Cell 06 - Address: BC:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"HOME-3A02" Extra: Last beacon: 4810ms ago
Cell 07 - Address: BE:34:26:53:51:EE Frequency:2.437 GHz (Channel 6) Quality=22/70  Signal level=-88 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 90ms ago
-----
Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=57/70  Signal level=-53 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 90ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=25/70  Signal level=-85 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 90ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 90ms ago
Cell 04 - Address: DC:EF:09:3C:ED:91 Frequency:2.412 GHz (Channel 1) Quality=18/70  Signal level=-92 dBm  Encryption key:on ESSID:"NETGEAR61_EXT" Extra: Last beacon: 90ms ago
Cell 05 - Address: BC:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"HOME-3A02" Extra: Last beacon: 9640ms ago
Cell 06 - Address: BE:34:26:53:51:EE Frequency:2.437 GHz (Channel 6) Quality=22/70  Signal level=-88 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 4920ms ago
-----
Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=57/70  Signal level=-53 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 100ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=22/70  Signal level=-88 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 100ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 100ms ago
Cell 04 - Address: DC:EF:09:3C:ED:91 Frequency:2.412 GHz (Channel 1) Quality=18/70  Signal level=-92 dBm  Encryption key:on ESSID:"NETGEAR61_EXT" Extra: Last beacon: 4820ms ago
Cell 05 - Address: BC:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=20/70  Signal level=-90 dBm  Encryption key:on ESSID:"HOME-3A02" Extra: Last beacon: 14370ms ago
Cell 06 - Address: BE:34:26:53:51:EE Frequency:2.437 GHz (Channel 6) Quality=22/70  Signal level=-88 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 9650ms ago
-----
Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=57/70  Signal level=-53 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 100ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 100ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 100ms ago
Cell 04 - Address: DC:EF:09:3C:ED:91 Frequency:2.412 GHz (Channel 1) Quality=18/70  Signal level=-92 dBm  Encryption key:on ESSID:"NETGEAR61_EXT" Extra: Last beacon: 9550ms ago
Cell 05 - Address: BE:34:26:53:51:EE Frequency:2.437 GHz (Channel 6) Quality=22/70  Signal level=-88 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 14380ms ago
Cell 06 - Address: 84:00:2D:57:E2:5B Frequency:2.437 GHz (Channel 6) Quality=20/70  Signal level=-90 dBm  Encryption key:off ESSID:"" Extra: Last beacon: 100ms ago
-----
Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=57/70  Signal level=-53 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 90ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 4870ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 90ms ago
Cell 04 - Address: DC:EF:09:3C:ED:91 Frequency:2.412 GHz (Channel 1) Quality=18/70  Signal level=-92 dBm  Encryption key:on ESSID:"NETGEAR61_EXT" Extra: Last beacon: 14320ms ago
Cell 05 - Address: 84:00:2D:57:E2:5B Frequency:2.437 GHz (Channel 6) Quality=20/70  Signal level=-90 dBm  Encryption key:off ESSID:"" Extra: Last beacon: 4870ms ago
Cell 06 - Address: BC:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"HOME-3A02" Extra: Last beacon: 90ms ago
Cell 07 - Address: B2:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 90ms ago
Cell 08 - Address: 02:1D:D5:8B:AC:50 Frequency:2.412 GHz (Channel 1) Quality=21/70  Signal level=-89 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 90ms ago
-----
Cell 01 - Address: 78:24:AF:7A:F1:04 Frequency:5.2 GHz (Channel 40) Quality=58/70  Signal level=-52 dBm  Encryption key:on ESSID:"ASUS_5G" Extra: Last beacon: 100ms ago
Cell 02 - Address: 08:86:3B:22:8F:4C Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"LifeIsGood" Extra: Last beacon: 9680ms ago
Cell 03 - Address: 78:24:AF:7A:F1:00 Frequency:2.442 GHz (Channel 7) Quality=64/70  Signal level=-46 dBm  Encryption key:on ESSID:"ASUS-24" Extra: Last beacon: 100ms ago
Cell 04 - Address: 84:00:2D:57:E2:5B Frequency:2.437 GHz (Channel 6) Quality=20/70  Signal level=-90 dBm  Encryption key:off ESSID:"" Extra: Last beacon: 9680ms ago
Cell 05 - Address: BC:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"HOME-3A02" Extra: Last beacon: 4900ms ago
Cell 06 - Address: B2:CA:B5:AA:3A:00 Frequency:2.412 GHz (Channel 1) Quality=70/70  Signal level=0 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 4900ms ago
Cell 07 - Address: 02:1D:D5:8B:AC:50 Frequency:2.412 GHz (Channel 1) Quality=21/70  Signal level=-89 dBm  Encryption key:on ESSID:"" Extra: Last beacon: 4900ms ago

I couldn’t answer your question, but I’m curious about whether you are using anything PCIe? I’m curious about whether there is a noise relationship. If there is anything PCIe, it might be of interest to see if you have the same issues with the PCIe device removed.

nope. No PCIe devices. The issue occurs both in the lab and in the field with completely different RF environments. The TX-1 can be mounted on a stock dev kit or on our Leopard Imaging carrier cards with multiple sensors and the same issue occurs.

Hi sperok,

I just tried the scripts on my device. However, I cannot see duplicate ghost SSID…

Found the problem - Chromecast devices with Guest Accesss enabled generate these bogus SSID’s.