I know that the link quality indicates the packet drops, errors etc. But when it tells me that link quality is "31/70", what is '31' and what is '70'?
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In the code for iwinfo, a newer tool similar to iwconfig, is a comment that states:
/* The cfg80211 wext compat layer assumes a signal range of -110 dBm to -40 dBm, the quality value is derived by adding 110 to the signal level */
Adding 110 moves the minimum value to 0 to simplify the presentation of the range and thus moves the maximum to 70. To convert signal strength to a percentage [0,100], do:
quality_percent = (signal_strength + 110) * 10 / 7
In one of the functions, the quality value is stored in a variable named rssi which is an acronym for received signal strength indication, "an indication of the power level (signal strength in arbitrary units) being received by the receive radio after the antenna and possible cable loss."
Speaking of "wext" (in the aforementioned code's comment) and iwconfig, in 2015, Wireless-Extensions (WE or Wext) and its tools including iwconfig were abandoned by the Linux kernel wireless developers. Its replacements are cfg80211 and nl80211, and the tool they strongly recommend is iw.
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