This question was asked a year and a half ago with no response nor related threads I could find.

What does the "Link Quality" number in the mesh status represent?

And,

Do the Signal/Noise/Ratio numbers in the signal strength page reflect anything close to reality in dB?

Thanks

Hello Mark,

The LQ (Link Quality) number is provided by the OLSR routing daemon (which makes the decisions of what is the best way to get to each node in the mesh)

The LQ variable is the measure of the quality of the link from the remote node TO  your node.

It is basically based on how likely a packet sent from the remote node is to make it to you.  If it shows 70% you have a 30% chance that any packet sent from that node to you will need to be resent because it was lost being sent to you.

Signal Strength has a lot of impact on LQ, local noise on your side from other wifi devices etc will have an impact as well (Wifi is a Carrier Sense Multiple Access protocol -- However most indoor nodes will NOT hear your far away remote sender so they will NOT sense the channel is in use and as such they can double on top of the packet you are trying to receive)

As far as I know the signal levels are fairly accurate.  They are not a spectrum analyzer so I wouldn't use it to say "this device transmits at X watts"   but it should be close enough for discussion of figuring out how strong a receive signal you have.

Thanks for that info Conrad, that's what I was looking for.

The from/to aspect of it explains why often I see the LQ between two nodes is not reciprocal.  Likely explained by co-channel interference at one node but not the other.

I suspect anything other than 100% will have an impact to throughput.

LQ doesn't actually tell you about throughput.

The fact is that a negotiated link at 24mbps with with 20% losses (an LQ of 80%) can actually handle more successful traffic (throughput) than a link at 11mbps with no loss (100 % LQ) because of the speed advantage.

LQ simply tells you the probability of what you send making it to the next hop. Nothing more nothing less.  A throughput measure requires a link speed knowledge which can change for each packet in the wifi world as the radios adjust to changing conditions