Why Linux WiFi indicator shows low signal strength

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Related: Wifi performance at low signal strength


You may wonder why Linux shows less than full “signal bars” for Wifi, even for a device relatively close to the Wifi AP (Access Point, the “router”). The answer is that the Linux desktop GUI is being honest about the quality of the connection, which is immediately relevant to the data throughput and connection latency. The end user shouldn’t care as much about raw RF signal strength (e.g. -70 dBm) as they should about the quality (SNR) of that connection. Of course, low signal strength < -80 dBm also causes low SNR and hence decreased link quality, even in relatively clear Wifi signal environments.

Unfortunately, many OEMs (and tech websites on click-commission) have duped people into buying expensive individual APs instead of quality sub-$100 APs (such as from Ubiquiti ) that can be distributed evenly throughout the home or office. You actually typically want to lower transmit power from the default level to around +18..+21 dBm to help the user devices roam between APs for best performance, and to disconnect promptly as a user moves off-premises.

In a particular client site with suboptimally configured Wifi network, I can see in my GNOME desktop environment (and also in Unity desktop) that I have 2 out of 3 signal bars for WiFi, despite being connected at MCS index 15 to an 802.11n AP on 5 GHz with a signal strength approaching -50 dBm. MCS 15 is the fastest possible connection for 802.11n, so why does GNOME/Unity show only moderate “signal bars”? This is because there are very many other high utilization APs on the same channel so that SNR (“link quality” for many Wifi cards in iwconfig) is low (less than say 0.7 normalized).

Summary

Home and business Wifi users will virtually always get better performance from:

  • multiple low-power APs instead of single high-power AP
  • 5 GHz instead of 2.4 GHz
  • APs set to the clearest possible Wifi channels (such as DFS)
  • APs placed as much as possible to interior of environment, high on wall or ceiling
  • iterative tuning of the system to minimize co-channel high utilization APs

The goal is for the AP to not “hear” other off-premises Wifi or other on-channel wireless activity, since generally the AP due to siting and high performance chipset “hears” significantly better than the end user devices.

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